/* Copyright (c) 2004-2008, Sara Golemon <sarag@libssh2.org>
 * Copyright (c) 2007 Eli Fant <elifantu@mail.ru>
 * Copyright (c) 2009-2010 by Daniel Stenberg
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms,
 * with or without modification, are permitted provided
 * that the following conditions are met:
 *
 *   Redistributions of source code must retain the above
 *   copyright notice, this list of conditions and the
 *   following disclaimer.
 *
 *   Redistributions in binary form must reproduce the above
 *   copyright notice, this list of conditions and the following
 *   disclaimer in the documentation and/or other materials
 *   provided with the distribution.
 *
 *   Neither the name of the copyright holder nor the names
 *   of any other contributors may be used to endorse or
 *   promote products derived from this software without
 *   specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
 * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
 * USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
 * OF SUCH DAMAGE.
 */

#include <assert.h>

#include "libssh2_priv.h"
#include "libssh2_sftp.h"
#include "channel.h"
#include "session.h"
#include "sftp.h"

/* Note: Version 6 was documented at the time of writing
 * However it was marked as "DO NOT IMPLEMENT" due to pending changes
 *
 * This release of libssh2 implements Version 5 with automatic downgrade
 * based on server's declaration
 */

/* SFTP packet types */
#define SSH_FXP_INIT                            1
#define SSH_FXP_VERSION                         2
#define SSH_FXP_OPEN                            3
#define SSH_FXP_CLOSE                           4
#define SSH_FXP_READ                            5
#define SSH_FXP_WRITE                           6
#define SSH_FXP_LSTAT                           7
#define SSH_FXP_FSTAT                           8
#define SSH_FXP_SETSTAT                         9
#define SSH_FXP_FSETSTAT                        10
#define SSH_FXP_OPENDIR                         11
#define SSH_FXP_READDIR                         12
#define SSH_FXP_REMOVE                          13
#define SSH_FXP_MKDIR                           14
#define SSH_FXP_RMDIR                           15
#define SSH_FXP_REALPATH                        16
#define SSH_FXP_STAT                            17
#define SSH_FXP_RENAME                          18
#define SSH_FXP_READLINK                        19
#define SSH_FXP_SYMLINK                         20
#define SSH_FXP_STATUS                          101
#define SSH_FXP_HANDLE                          102
#define SSH_FXP_DATA                            103
#define SSH_FXP_NAME                            104
#define SSH_FXP_ATTRS                           105
#define SSH_FXP_EXTENDED                        200
#define SSH_FXP_EXTENDED_REPLY                  201

/* S_IFREG */
#define LIBSSH2_SFTP_ATTR_PFILETYPE_FILE        0100000
/* S_IFDIR */
#define LIBSSH2_SFTP_ATTR_PFILETYPE_DIR         0040000

#define SSH_FXE_STATVFS_ST_RDONLY               0x00000001
#define SSH_FXE_STATVFS_ST_NOSUID               0x00000002

static int sftp_close_handle(LIBSSH2_SFTP_HANDLE *handle);
static int sftp_packet_ask(LIBSSH2_SFTP *sftp, unsigned char packet_type,
                           uint32_t request_id, unsigned char **data,
                           size_t *data_len);
static void sftp_packet_flush(LIBSSH2_SFTP *sftp);

/* sftp_attrsize
 * Size that attr with this flagset will occupy when turned into a bin struct
 */
static int sftp_attrsize(unsigned long flags)
{
    return (4 +                                 /* flags(4) */
            ((flags & LIBSSH2_SFTP_ATTR_SIZE) ? 8 : 0) +
            ((flags & LIBSSH2_SFTP_ATTR_UIDGID) ? 8 : 0) +
            ((flags & LIBSSH2_SFTP_ATTR_PERMISSIONS) ? 4 : 0) +
            ((flags & LIBSSH2_SFTP_ATTR_ACMODTIME) ? 8 : 0));
                                                /* atime + mtime as u32 */
}

/* _libssh2_store_u64
 */
static void _libssh2_store_u64(unsigned char **ptr, libssh2_uint64_t value)
{
    uint32_t msl = (uint32_t)(value >> 32);
    unsigned char *buf = *ptr;

    buf[0] = (unsigned char)((msl >> 24) & 0xFF);
    buf[1] = (unsigned char)((msl >> 16) & 0xFF);
    buf[2] = (unsigned char)((msl >> 8)  & 0xFF);
    buf[3] = (unsigned char)( msl        & 0xFF);

    buf[4] = (unsigned char)((value >> 24) & 0xFF);
    buf[5] = (unsigned char)((value >> 16) & 0xFF);
    buf[6] = (unsigned char)((value >> 8)  & 0xFF);
    buf[7] = (unsigned char)( value        & 0xFF);

    *ptr += 8;
}

/*
 * sftp_packet_add
 *
 * Add a packet to the SFTP packet brigade
 */
static int
sftp_packet_add(LIBSSH2_SFTP *sftp, unsigned char *data,
                size_t data_len)
{
    LIBSSH2_SESSION *session = sftp->channel->session;
    LIBSSH2_SFTP_PACKET *packet;

    _libssh2_debug(session, LIBSSH2_TRACE_SFTP, "Received packet %d (len %d)",
                   (int) data[0], data_len);
    packet = LIBSSH2_ALLOC(session, sizeof(LIBSSH2_SFTP_PACKET));
    if (!packet) {
        return _libssh2_error(session, LIBSSH2_ERROR_ALLOC,
                              "Unable to allocate datablock for SFTP packet");
    }

    packet->data = data;
    packet->data_len = data_len;
    packet->request_id = _libssh2_ntohu32(&data[1]);

    _libssh2_list_add(&sftp->packets, &packet->node);

    return 0;
}

/*
 * sftp_packet_read
 *
 * Frame an SFTP packet off the channel
 */
static int
sftp_packet_read(LIBSSH2_SFTP *sftp)
{
    LIBSSH2_CHANNEL *channel = sftp->channel;
    LIBSSH2_SESSION *session = channel->session;
    unsigned char *packet;
    size_t packet_received;
    ssize_t rc;
    uint32_t packet_len; /* 32bits on the wire */

    _libssh2_debug(session, LIBSSH2_TRACE_SFTP, "recv packet");

    /* If there was a previous partial, start using it */
    if (sftp->partial_packet) {

        packet = sftp->partial_packet;
        packet_len = sftp->partial_len;
        packet_received = sftp->partial_received;
        sftp->partial_packet = NULL;

        _libssh2_debug(session, LIBSSH2_TRACE_SFTP,
                       "partial read cont, len: %lu", packet_len);
    }
    else {
        /* each packet starts with a 32 bit length field */
        rc = _libssh2_channel_read(channel, 0,
                                   (char *)&sftp->partial_size[
                                       sftp->partial_size_len],
                                   4 - sftp->partial_size_len);
        if (rc == LIBSSH2_ERROR_EAGAIN)
            return rc;
        else if (rc < 0)
            return _libssh2_error(session, rc, "channel read");

        sftp->partial_size_len += rc;

        if(4 != sftp->partial_size_len)
            /* we got a short read for the length part */
            return LIBSSH2_ERROR_EAGAIN;

        packet_len = _libssh2_ntohu32(sftp->partial_size);
        /* make sure we don't proceed if the packet size is unreasonably
           large */
        if (packet_len > LIBSSH2_SFTP_PACKET_MAXLEN)
            return _libssh2_error(session,
                                  LIBSSH2_ERROR_CHANNEL_PACKET_EXCEEDED,
                                  "SFTP packet too large");

        _libssh2_debug(session, LIBSSH2_TRACE_SFTP,
                       "Data begin - Packet Length: %lu", packet_len);
        packet = LIBSSH2_ALLOC(session, packet_len);
        if (!packet)
            return _libssh2_error(session, LIBSSH2_ERROR_ALLOC,
                                  "Unable to allocate SFTP packet");
        sftp->partial_size_len = 0;
        packet_received = 0;
    }

    /* Read as much of the packet as we can */
    while (packet_len > packet_received) {
        rc = _libssh2_channel_read(channel, 0,
                                   (char *) packet + packet_received,
                                   packet_len - packet_received);

        if (rc == LIBSSH2_ERROR_EAGAIN) {
            /*
             * We received EAGAIN, save what we have and return EAGAIN to the
             * caller
             */
            sftp->partial_packet = packet;
            sftp->partial_len = packet_len;
            sftp->partial_received = packet_received;
            return rc;
        }
        else if (rc < 0) {
            LIBSSH2_FREE(session, packet);
            return _libssh2_error(session, rc,
                                  "Error waiting for SFTP packet");
        }
        packet_received += rc;
    }

    sftp->partial_packet = NULL;

    rc = sftp_packet_add(sftp, packet, packet_len);
    if (rc) {
        LIBSSH2_FREE(session, packet);
        return rc;
    }

    return packet[0];
}
/*
 * sftp_packetlist_flush
 *
 * Remove all pending packets in the packet_list and the corresponding one(s)
 * in the SFTP packet brigade.
 */
static void sftp_packetlist_flush(LIBSSH2_SFTP_HANDLE *handle)
{
    struct sftp_pipeline_chunk *chunk;
    LIBSSH2_SFTP *sftp = handle->sftp;
    LIBSSH2_SESSION *session = sftp->channel->session;

    /* remove pending packets, if any */
    chunk = _libssh2_list_first(&handle->packet_list);
    while(chunk) {
        unsigned char *data;
        size_t data_len;
        int rc;
        struct sftp_pipeline_chunk *next = _libssh2_list_next(&chunk->node);

        rc = sftp_packet_ask(sftp, SSH_FXP_STATUS,
                             chunk->request_id, &data, &data_len);
        if(rc)
            rc = sftp_packet_ask(sftp, SSH_FXP_DATA,
                                 chunk->request_id, &data, &data_len);

        if(!rc)
            /* we found a packet, free it */
            LIBSSH2_FREE(session, data);

        _libssh2_list_remove(&chunk->node);
        LIBSSH2_FREE(session, chunk);
        chunk = next;
    }
}


/*
 * sftp_packet_ask()
 *
 * Checks if there's a matching SFTP packet available.
 */
static int
sftp_packet_ask(LIBSSH2_SFTP *sftp, unsigned char packet_type,
                uint32_t request_id, unsigned char **data,
                size_t *data_len)
{
    LIBSSH2_SESSION *session = sftp->channel->session;
    LIBSSH2_SFTP_PACKET *packet = _libssh2_list_first(&sftp->packets);

    if(!packet)
        return -1;

    /* Special consideration when getting VERSION packet */

    while (packet) {
        if((packet->data[0] == packet_type) &&
           ((packet_type == SSH_FXP_VERSION) ||
            (packet->request_id == request_id))) {

            /* Match! Fetch the data */
            *data = packet->data;
            *data_len = packet->data_len;

            /* unlink and free this struct */
            _libssh2_list_remove(&packet->node);
            LIBSSH2_FREE(session, packet);

            return 0;
        }
        /* check next struct in the list */
        packet = _libssh2_list_next(&packet->node);
    }
    return -1;
}

/* sftp_packet_require
 * A la libssh2_packet_require
 */
static int
sftp_packet_require(LIBSSH2_SFTP *sftp, unsigned char packet_type,
                    uint32_t request_id, unsigned char **data,
                    size_t *data_len)
{
    LIBSSH2_SESSION *session = sftp->channel->session;
    int rc;

    _libssh2_debug(session, LIBSSH2_TRACE_SFTP, "Requiring packet %d id %ld",
                   (int) packet_type, request_id);

    if (sftp_packet_ask(sftp, packet_type, request_id, data, data_len) == 0) {
        /* The right packet was available in the packet brigade */
        _libssh2_debug(session, LIBSSH2_TRACE_SFTP, "Got %d",
                       (int) packet_type);
        return LIBSSH2_ERROR_NONE;
    }

    while (session->socket_state == LIBSSH2_SOCKET_CONNECTED) {
        rc = sftp_packet_read(sftp);
        if (rc == LIBSSH2_ERROR_EAGAIN)
            return rc;
        else if (rc <= 0)
            /* TODO: isn't this supposed to be < 0 only? */
            return rc;

        /* data was read, check the queue again */
        if (!sftp_packet_ask(sftp, packet_type, request_id, data, data_len)) {
            /* The right packet was available in the packet brigade */
            _libssh2_debug(session, LIBSSH2_TRACE_SFTP, "Got %d",
                           (int) packet_type);
            return LIBSSH2_ERROR_NONE;
        }
    }

    /* Only reached if the socket died */
    return LIBSSH2_ERROR_SOCKET_DISCONNECT;
}

/* sftp_packet_requirev
 * Require one of N possible reponses
 */
static int
sftp_packet_requirev(LIBSSH2_SFTP *sftp, int num_valid_responses,
                     const unsigned char *valid_responses,
                     uint32_t request_id, unsigned char **data,
                     size_t *data_len)
{
    int i;
    int rc;

    /* If no timeout is active, start a new one */
    if (sftp->requirev_start == 0)
        sftp->requirev_start = time(NULL);

    while (sftp->channel->session->socket_state == LIBSSH2_SOCKET_CONNECTED) {
        for(i = 0; i < num_valid_responses; i++) {
            if (sftp_packet_ask(sftp, valid_responses[i], request_id,
                                data, data_len) == 0) {
                /*
                 * Set to zero before all returns to say
                 * the timeout is not active
                 */
                sftp->requirev_start = 0;
                return LIBSSH2_ERROR_NONE;
            }
        }

        rc = sftp_packet_read(sftp);
        if ((rc < 0) && (rc != LIBSSH2_ERROR_EAGAIN)) {
            sftp->requirev_start = 0;
            return rc;
        } else if (rc <= 0) {
            /* prevent busy-looping */
            long left =
                LIBSSH2_READ_TIMEOUT - (long)(time(NULL) - sftp->requirev_start);

            if (left <= 0) {
                sftp->requirev_start = 0;
                return LIBSSH2_ERROR_TIMEOUT;
            }
            else if (rc == LIBSSH2_ERROR_EAGAIN) {
                return rc;
            }
        }
    }

    sftp->requirev_start = 0;

    /* Only reached if the socket died */
    return LIBSSH2_ERROR_SOCKET_DISCONNECT;
}

/* sftp_attr2bin
 * Populate attributes into an SFTP block
 */
static ssize_t
sftp_attr2bin(unsigned char *p, const LIBSSH2_SFTP_ATTRIBUTES * attrs)
{
    unsigned char *s = p;
    uint32_t flag_mask =
        LIBSSH2_SFTP_ATTR_SIZE | LIBSSH2_SFTP_ATTR_UIDGID |
        LIBSSH2_SFTP_ATTR_PERMISSIONS | LIBSSH2_SFTP_ATTR_ACMODTIME;

    /* TODO: When we add SFTP4+ functionality flag_mask can get additional
       bits */

    if (!attrs) {
        _libssh2_htonu32(s, 0);
        return 4;
    }

    _libssh2_store_u32(&s, attrs->flags & flag_mask);

    if (attrs->flags & LIBSSH2_SFTP_ATTR_SIZE) {
        _libssh2_store_u64(&s, attrs->filesize);
    }

    if (attrs->flags & LIBSSH2_SFTP_ATTR_UIDGID) {
        _libssh2_store_u32(&s, attrs->uid);
        _libssh2_store_u32(&s, attrs->gid);
    }

    if (attrs->flags & LIBSSH2_SFTP_ATTR_PERMISSIONS) {
        _libssh2_store_u32(&s, attrs->permissions);
    }

    if (attrs->flags & LIBSSH2_SFTP_ATTR_ACMODTIME) {
        _libssh2_store_u32(&s, attrs->atime);
        _libssh2_store_u32(&s, attrs->mtime);
    }

    return (s - p);
}

/* sftp_bin2attr
 */
static int
sftp_bin2attr(LIBSSH2_SFTP_ATTRIBUTES * attrs, const unsigned char *p)
{
    const unsigned char *s = p;

    memset(attrs, 0, sizeof(LIBSSH2_SFTP_ATTRIBUTES));
    attrs->flags = _libssh2_ntohu32(s);
    s += 4;

    if (attrs->flags & LIBSSH2_SFTP_ATTR_SIZE) {
        attrs->filesize = _libssh2_ntohu64(s);
        s += 8;
    }

    if (attrs->flags & LIBSSH2_SFTP_ATTR_UIDGID) {
        attrs->uid = _libssh2_ntohu32(s);
        s += 4;
        attrs->gid = _libssh2_ntohu32(s);
        s += 4;
    }

    if (attrs->flags & LIBSSH2_SFTP_ATTR_PERMISSIONS) {
        attrs->permissions = _libssh2_ntohu32(s);
        s += 4;
    }

    if (attrs->flags & LIBSSH2_SFTP_ATTR_ACMODTIME) {
        attrs->atime = _libssh2_ntohu32(s);
        s += 4;
        attrs->mtime = _libssh2_ntohu32(s);
        s += 4;
    }

    return (s - p);
}

/* ************
 * SFTP API *
 ************ */

LIBSSH2_CHANNEL_CLOSE_FUNC(libssh2_sftp_dtor);

/* libssh2_sftp_dtor
 * Shutdown an SFTP stream when the channel closes
 */
LIBSSH2_CHANNEL_CLOSE_FUNC(libssh2_sftp_dtor)
{
    LIBSSH2_SFTP *sftp = (LIBSSH2_SFTP *) (*channel_abstract);

    (void) session_abstract;
    (void) channel;

    /* Free the partial packet storage for sftp_packet_read */
    if (sftp->partial_packet) {
        LIBSSH2_FREE(session, sftp->partial_packet);
    }

    /* Free the packet storage for _libssh2_sftp_packet_readdir */
    if (sftp->readdir_packet) {
        LIBSSH2_FREE(session, sftp->readdir_packet);
    }

    LIBSSH2_FREE(session, sftp);
}

/*
 * sftp_init
 *
 * Startup an SFTP session
 */
static LIBSSH2_SFTP *sftp_init(LIBSSH2_SESSION *session)
{
    unsigned char *data, *s;
    size_t data_len;
    ssize_t rc;
    LIBSSH2_SFTP *sftp_handle;

    if (session->sftpInit_state == libssh2_NB_state_idle) {
        _libssh2_debug(session, LIBSSH2_TRACE_SFTP,
                       "Initializing SFTP subsystem");

        /*
         * The 'sftpInit_sftp' and 'sftpInit_channel' struct fields within the
         * session struct are only to be used during the setup phase. As soon
         * as the SFTP session is created they are cleared and can thus be
         * re-used again to allow any amount of SFTP handles per sessions.
         *
         * Note that you MUST NOT try to call libssh2_sftp_init() again to get
         * another handle until the previous call has finished and either
         * succesffully made a handle or failed and returned error (not
         * including *EAGAIN).
         */

        assert(session->sftpInit_sftp == NULL);
        session->sftpInit_sftp = NULL;
        session->sftpInit_state = libssh2_NB_state_created;
    }

    sftp_handle = session->sftpInit_sftp;

    if (session->sftpInit_state == libssh2_NB_state_created) {
        session->sftpInit_channel =
            _libssh2_channel_open(session, "session", sizeof("session") - 1,
                                  LIBSSH2_CHANNEL_WINDOW_DEFAULT,
                                  LIBSSH2_CHANNEL_PACKET_DEFAULT, NULL, 0);
        if (!session->sftpInit_channel) {
            if (libssh2_session_last_errno(session) == LIBSSH2_ERROR_EAGAIN) {
                _libssh2_error(session, LIBSSH2_ERROR_EAGAIN,
                               "Would block starting up channel");
            }
            else {
                _libssh2_error(session, LIBSSH2_ERROR_CHANNEL_FAILURE,
                               "Unable to startup channel");
                session->sftpInit_state = libssh2_NB_state_idle;
            }
            return NULL;
        }

        session->sftpInit_state = libssh2_NB_state_sent;
    }

    if (session->sftpInit_state == libssh2_NB_state_sent) {
        int ret = _libssh2_channel_process_startup(session->sftpInit_channel,
                                                   "subsystem",
                                                   sizeof("subsystem") - 1, "sftp",
                                                   strlen("sftp"));
        if (ret == LIBSSH2_ERROR_EAGAIN) {
            _libssh2_error(session, LIBSSH2_ERROR_EAGAIN,
                           "Would block to request SFTP subsystem");
            return NULL;
        } else if (ret) {
            _libssh2_error(session, LIBSSH2_ERROR_CHANNEL_FAILURE,
                           "Unable to request SFTP subsystem");
            goto sftp_init_error;
        }

        session->sftpInit_state = libssh2_NB_state_sent1;
    }

    if (session->sftpInit_state == libssh2_NB_state_sent1) {
        rc = _libssh2_channel_extended_data(session->sftpInit_channel,
                                            LIBSSH2_CHANNEL_EXTENDED_DATA_IGNORE);
        if (rc == LIBSSH2_ERROR_EAGAIN) {
            _libssh2_error(session, LIBSSH2_ERROR_EAGAIN,
                           "Would block requesting handle extended data");
            return NULL;
        }

        sftp_handle =
            session->sftpInit_sftp =
            LIBSSH2_ALLOC(session, sizeof(LIBSSH2_SFTP));
        if (!sftp_handle) {
            _libssh2_error(session, LIBSSH2_ERROR_ALLOC,
                           "Unable to allocate a new SFTP structure");
            goto sftp_init_error;
        }
        memset(sftp_handle, 0, sizeof(LIBSSH2_SFTP));
        sftp_handle->channel = session->sftpInit_channel;
        sftp_handle->request_id = 0;

        _libssh2_htonu32(session->sftpInit_buffer, 5);
        session->sftpInit_buffer[4] = SSH_FXP_INIT;
        _libssh2_htonu32(session->sftpInit_buffer + 5, LIBSSH2_SFTP_VERSION);
        session->sftpInit_sent = 0; /* nothing's sent yet */

        _libssh2_debug(session, LIBSSH2_TRACE_SFTP,
                       "Sending FXP_INIT packet advertising version %d support",
                       (int) LIBSSH2_SFTP_VERSION);

        session->sftpInit_state = libssh2_NB_state_sent2;
    }

    if (session->sftpInit_state == libssh2_NB_state_sent2) {
        /* sent off what's left of the init buffer to send */
        rc = _libssh2_channel_write(session->sftpInit_channel, 0,
                                    session->sftpInit_buffer +
                                    session->sftpInit_sent,
                                    9 - session->sftpInit_sent);
        if (rc == LIBSSH2_ERROR_EAGAIN) {
            _libssh2_error(session, LIBSSH2_ERROR_EAGAIN,
                           "Would block sending SSH_FXP_INIT");
            return NULL;
        }
        else if(rc < 0) {
            _libssh2_error(session, LIBSSH2_ERROR_SOCKET_SEND,
                           "Unable to send SSH_FXP_INIT");
            goto sftp_init_error;
        }
        else {
            /* add up the number of bytes sent */
            session->sftpInit_sent += rc;

            if(session->sftpInit_sent == 9)
                /* move on */
                session->sftpInit_state = libssh2_NB_state_sent3;

            /* if less than 9, we remain in this state to send more later on */
        }
    }

    rc = sftp_packet_require(sftp_handle, SSH_FXP_VERSION,
                             0, &data, &data_len);
    if (rc == LIBSSH2_ERROR_EAGAIN) {
        _libssh2_error(session, LIBSSH2_ERROR_EAGAIN,
                       "Would block waiting for response from SFTP subsystem");
        return NULL;
    } else if (rc) {
        _libssh2_error(session, LIBSSH2_ERROR_SOCKET_TIMEOUT,
                       "Timeout waiting for response from SFTP subsystem");
        goto sftp_init_error;
    }
    if (data_len < 5) {
        _libssh2_error(session, LIBSSH2_ERROR_SFTP_PROTOCOL,
                       "Invalid SSH_FXP_VERSION response");
        goto sftp_init_error;
    }

    s = data + 1;
    sftp_handle->version = _libssh2_ntohu32(s);
    s += 4;
    if (sftp_handle->version > LIBSSH2_SFTP_VERSION) {
        _libssh2_debug(session, LIBSSH2_TRACE_SFTP,
                       "Truncating remote SFTP version from %lu",
                       sftp_handle->version);
        sftp_handle->version = LIBSSH2_SFTP_VERSION;
    }
    _libssh2_debug(session, LIBSSH2_TRACE_SFTP,
                   "Enabling SFTP version %lu compatability",
                   sftp_handle->version);
    while (s < (data + data_len)) {
        size_t extname_len, extdata_len;

        extname_len = _libssh2_ntohu32(s);
        s += 4;
        /* the extension name starts here */
        s += extname_len;

        extdata_len = _libssh2_ntohu32(s);
        s += 4;

        /* TODO: Actually process extensions */
        s += extdata_len;

    }
    LIBSSH2_FREE(session, data);

    /* Make sure that when the channel gets closed, the SFTP service is shut
       down too */
    sftp_handle->channel->abstract = sftp_handle;
    sftp_handle->channel->close_cb = libssh2_sftp_dtor;

    session->sftpInit_state = libssh2_NB_state_idle;

    /* clear the sftp and channel pointers in this session struct now */
    session->sftpInit_sftp = NULL;
    session->sftpInit_channel = NULL;

    _libssh2_list_init(&sftp_handle->sftp_handles);

    return sftp_handle;

  sftp_init_error:
    while (_libssh2_channel_free(session->sftpInit_channel) ==
           LIBSSH2_ERROR_EAGAIN);
    session->sftpInit_channel = NULL;
    if (session->sftpInit_sftp) {
        LIBSSH2_FREE(session, session->sftpInit_sftp);
        session->sftpInit_sftp = NULL;
    }
    session->sftpInit_state = libssh2_NB_state_idle;
    return NULL;
}

/*
 * libssh2_sftp_init
 *
 * Startup an SFTP session
 */
LIBSSH2_API LIBSSH2_SFTP *libssh2_sftp_init(LIBSSH2_SESSION *session)
{
    LIBSSH2_SFTP *ptr;

    if(!session)
        return NULL;

    if(!(session->state & LIBSSH2_STATE_AUTHENTICATED)) {
        _libssh2_error(session, LIBSSH2_ERROR_INVAL,
                       "session not authenticated yet");
        return NULL;
    }

    BLOCK_ADJUST_ERRNO(ptr, session, sftp_init(session));
    return ptr;
}

/*
 * sftp_shutdown
 *
 * Shutsdown the SFTP subsystem
 */
static int
sftp_shutdown(LIBSSH2_SFTP *sftp)
{
    int rc;
    LIBSSH2_SESSION *session = sftp->channel->session;
    /*
     * Make sure all memory used in the state variables are free
     */
    if (sftp->partial_packet) {
        LIBSSH2_FREE(session, sftp->partial_packet);
        sftp->partial_packet = NULL;
    }
    if (sftp->open_packet) {
        LIBSSH2_FREE(session, sftp->open_packet);
        sftp->open_packet = NULL;
    }
    if (sftp->readdir_packet) {
        LIBSSH2_FREE(session, sftp->readdir_packet);
        sftp->readdir_packet = NULL;
    }
    if (sftp->fstat_packet) {
        LIBSSH2_FREE(session, sftp->fstat_packet);
        sftp->fstat_packet = NULL;
    }
    if (sftp->unlink_packet) {
        LIBSSH2_FREE(session, sftp->unlink_packet);
        sftp->unlink_packet = NULL;
    }
    if (sftp->rename_packet) {
        LIBSSH2_FREE(session, sftp->rename_packet);
        sftp->rename_packet = NULL;
    }
    if (sftp->fstatvfs_packet) {
        LIBSSH2_FREE(session, sftp->fstatvfs_packet);
        sftp->fstatvfs_packet = NULL;
    }
    if (sftp->statvfs_packet) {
        LIBSSH2_FREE(session, sftp->statvfs_packet);
        sftp->statvfs_packet = NULL;
    }
    if (sftp->mkdir_packet) {
        LIBSSH2_FREE(session, sftp->mkdir_packet);
        sftp->mkdir_packet = NULL;
    }
    if (sftp->rmdir_packet) {
        LIBSSH2_FREE(session, sftp->rmdir_packet);
        sftp->rmdir_packet = NULL;
    }
    if (sftp->stat_packet) {
        LIBSSH2_FREE(session, sftp->stat_packet);
        sftp->stat_packet = NULL;
    }
    if (sftp->symlink_packet) {
        LIBSSH2_FREE(session, sftp->symlink_packet);
        sftp->symlink_packet = NULL;
    }

    sftp_packet_flush(sftp);

    /* TODO: We should consider walking over the sftp_handles list and kill
     * any remaining sftp handles ... */

    rc = _libssh2_channel_free(sftp->channel);

    return rc;
}

/* libssh2_sftp_shutdown
 * Shutsdown the SFTP subsystem
 */
LIBSSH2_API int
libssh2_sftp_shutdown(LIBSSH2_SFTP *sftp)
{
    int rc;
    if(!sftp)
        return LIBSSH2_ERROR_BAD_USE;
    BLOCK_ADJUST(rc, sftp->channel->session, sftp_shutdown(sftp));
    return rc;
}

/* *******************************
 * SFTP File and Directory Ops *
 ******************************* */

/* sftp_open
 */
static LIBSSH2_SFTP_HANDLE *
sftp_open(LIBSSH2_SFTP *sftp, const char *filename,
          size_t filename_len, uint32_t flags, long mode,
          int open_type)
{
    LIBSSH2_CHANNEL *channel = sftp->channel;
    LIBSSH2_SESSION *session = channel->session;
    LIBSSH2_SFTP_HANDLE *fp;
    LIBSSH2_SFTP_ATTRIBUTES attrs = {
        LIBSSH2_SFTP_ATTR_PERMISSIONS, 0, 0, 0, 0, 0, 0
    };
    unsigned char *s;
    ssize_t rc;
    int open_file = (open_type == LIBSSH2_SFTP_OPENFILE)?1:0;

    if (sftp->open_state == libssh2_NB_state_idle) {
        /* packet_len(4) + packet_type(1) + request_id(4) + filename_len(4) +
           flags(4) */
        sftp->open_packet_len = filename_len + 13 +
            (open_file? (4 + sftp_attrsize(LIBSSH2_SFTP_ATTR_PERMISSIONS)) : 0);

        /* surprise! this starts out with nothing sent */
        sftp->open_packet_sent = 0;
        s = sftp->open_packet = LIBSSH2_ALLOC(session, sftp->open_packet_len);
        if (!sftp->open_packet) {
            _libssh2_error(session, LIBSSH2_ERROR_ALLOC,
                           "Unable to allocate memory for FXP_OPEN or "
                           "FXP_OPENDIR packet");
            return NULL;
        }
        /* Filetype in SFTP 3 and earlier */
        attrs.permissions = mode |
            (open_file ? LIBSSH2_SFTP_ATTR_PFILETYPE_FILE :
             LIBSSH2_SFTP_ATTR_PFILETYPE_DIR);

        _libssh2_store_u32(&s, sftp->open_packet_len - 4);
        *(s++) = open_file? SSH_FXP_OPEN : SSH_FXP_OPENDIR;
        sftp->open_request_id = sftp->request_id++;
        _libssh2_store_u32(&s, sftp->open_request_id);
        _libssh2_store_str(&s, filename, filename_len);

        if (open_file) {
            _libssh2_store_u32(&s, flags);
            s += sftp_attr2bin(s, &attrs);
        }

        _libssh2_debug(session, LIBSSH2_TRACE_SFTP, "Sending %s open request",
                       open_file? "file" : "directory");

        sftp->open_state = libssh2_NB_state_created;
    }

    if (sftp->open_state == libssh2_NB_state_created) {
        rc = _libssh2_channel_write(channel, 0, sftp->open_packet+
                                    sftp->open_packet_sent,
                                    sftp->open_packet_len -
                                    sftp->open_packet_sent);
        if (rc == LIBSSH2_ERROR_EAGAIN) {
            _libssh2_error(session, LIBSSH2_ERROR_EAGAIN,
                           "Would block sending FXP_OPEN or FXP_OPENDIR command");
            return NULL;
        }
        else if(rc < 0) {
            _libssh2_error(session, rc, "Unable to send FXP_OPEN*");
            LIBSSH2_FREE(session, sftp->open_packet);
            sftp->open_packet = NULL;
            sftp->open_state = libssh2_NB_state_idle;
            return NULL;
        }

        /* bump the sent counter and remain in this state until the whole
           data is off */
        sftp->open_packet_sent += rc;

        if(sftp->open_packet_len == sftp->open_packet_sent) {
            LIBSSH2_FREE(session, sftp->open_packet);
            sftp->open_packet = NULL;

            sftp->open_state = libssh2_NB_state_sent;
        }
    }

    if (sftp->open_state == libssh2_NB_state_sent) {
        size_t data_len;
        unsigned char *data;
        static const unsigned char fopen_responses[2] =
            { SSH_FXP_HANDLE, SSH_FXP_STATUS };
        rc = sftp_packet_requirev(sftp, 2, fopen_responses,
                                  sftp->open_request_id, &data,
                                  &data_len);
        if (rc == LIBSSH2_ERROR_EAGAIN) {
            _libssh2_error(session, LIBSSH2_ERROR_EAGAIN,
                           "Would block waiting for status message");
            return NULL;
        }
        sftp->open_state = libssh2_NB_state_idle;
        if (rc) {
            _libssh2_error(session, rc, "Timeout waiting for status message");
            return NULL;
        }

        /* OPEN can basically get STATUS or HANDLE back, where HANDLE implies
           a fine response while STATUS means error. It seems though that at
           times we get an SSH_FX_OK back in a STATUS, followed the "real"
           HANDLE so we need to properly deal with that. */
        if (data[0] == SSH_FXP_STATUS) {
            int badness = 1;

            if(data_len < 9) {
                _libssh2_error(session, LIBSSH2_ERROR_SFTP_PROTOCOL,
                               "Too small FXP_STATUS");
                LIBSSH2_FREE(session, data);
                return NULL;
            }

            sftp->last_errno = _libssh2_ntohu32(data + 5);

            if(LIBSSH2_FX_OK == sftp->last_errno) {
                _libssh2_debug(session, LIBSSH2_TRACE_SFTP, "got HANDLE FXOK!");

                LIBSSH2_FREE(session, data);

                /* silly situation, but check for a HANDLE */
                rc = sftp_packet_require(sftp, SSH_FXP_HANDLE,
                                         sftp->open_request_id, &data,
                                         &data_len);
                if(rc == LIBSSH2_ERROR_EAGAIN) {
                    /* go back to sent state and wait for something else */
                    sftp->open_state = libssh2_NB_state_sent;
                    return NULL;
                }
                else if(!rc)
                    /* we got the handle so this is not a bad situation */
                    badness = 0;
            }

            if(badness) {
                _libssh2_error(session, LIBSSH2_ERROR_SFTP_PROTOCOL,
                               "Failed opening remote file");
                _libssh2_debug(session, LIBSSH2_TRACE_SFTP, "got FXP_STATUS %d",
                               sftp->last_errno);
                LIBSSH2_FREE(session, data);
                return NULL;
            }
        }

        if(data_len < 10) {
            _libssh2_error(session, LIBSSH2_ERROR_SFTP_PROTOCOL,
                           "Too small FXP_HANDLE");
            LIBSSH2_FREE(session, data);
            return NULL;
        }

        fp = LIBSSH2_ALLOC(session, sizeof(LIBSSH2_SFTP_HANDLE));
        if (!fp) {
            _libssh2_error(session, LIBSSH2_ERROR_ALLOC,
                           "Unable to allocate new SFTP handle structure");
            LIBSSH2_FREE(session, data);
            return NULL;
        }
        memset(fp, 0, sizeof(LIBSSH2_SFTP_HANDLE));
        fp->handle_type = open_file ? LIBSSH2_SFTP_HANDLE_FILE :
            LIBSSH2_SFTP_HANDLE_DIR;

        fp->handle_len = _libssh2_ntohu32(data + 5);
        if (fp->handle_len > SFTP_HANDLE_MAXLEN)
            /* SFTP doesn't allow handles longer than 256 characters */
            fp->handle_len = SFTP_HANDLE_MAXLEN;

        if(fp->handle_len > (data_len - 9))
            /* do not reach beyond the end of the data we got */
            fp->handle_len = data_len - 9;

        memcpy(fp->handle, data + 9, fp->handle_len);

        LIBSSH2_FREE(session, data);

        /* add this file handle to the list kept in the sftp session */
        _libssh2_list_add(&sftp->sftp_handles, &fp->node);

        fp->sftp = sftp; /* point to the parent struct */

        fp->u.file.offset = 0;
        fp->u.file.offset_sent = 0;

        _libssh2_debug(session, LIBSSH2_TRACE_SFTP, "Open command successful");
        return fp;
    }
    return NULL;
}

/* libssh2_sftp_open_ex
 */
LIBSSH2_API LIBSSH2_SFTP_HANDLE *
libssh2_sftp_open_ex(LIBSSH2_SFTP *sftp, const char *filename,
                     unsigned int filename_len, unsigned long flags, long mode,
                     int open_type)
{
    LIBSSH2_SFTP_HANDLE *hnd;

    if(!sftp)
        return NULL;

    BLOCK_ADJUST_ERRNO(hnd, sftp->channel->session,
                       sftp_open(sftp, filename, filename_len, flags, mode,
                                 open_type));
    return hnd;
}

/*
 * sftp_read
 *
 * Read from an SFTP file handle
 *
 */
static ssize_t sftp_read(LIBSSH2_SFTP_HANDLE * handle, char *buffer,
                         size_t buffer_size)
{
    LIBSSH2_SFTP *sftp = handle->sftp;
    LIBSSH2_CHANNEL *channel = sftp->channel;
    LIBSSH2_SESSION *session = channel->session;
    size_t count = 0;
    struct sftp_pipeline_chunk *chunk;
    struct sftp_pipeline_chunk *next;
    ssize_t rc;
    size_t eagain = 0;
    size_t total_read = 0;
    struct _libssh2_sftp_handle_file_data *filep =
        &handle->u.file;

    /* Number of bytes asked for that haven't been acked yet */
    size_t already = (filep->offset_sent - filep->offset);

    if(filep->data_left) {
        /* data left from previous call */
        size_t copy = MIN(buffer_size, filep->data_left);

        memcpy(buffer, &filep->data[ filep->data_len - filep->data_left],
               copy);

        total_read += copy;
        filep->data_left -= copy;

        if(filep->data_left)
            return total_read;

        LIBSSH2_FREE(session, filep->data);
        filep->data = NULL;
    }

    /* We allow a number of bytes being requested at any given time without
       having been acked - until we reach EOF. */
    if(!filep->eof) {
        /* if the buffer_size passed in now is smaller than what has already
           been sent, we risk getting count become a very large number */
        if((buffer_size*4) > already)
            count = (buffer_size*4) - already;
    }

    while(count > 0) {
        unsigned char *s;
        uint32_t size = MIN(MAX_SFTP_READ_SIZE, count);

        /* 25 = packet_len(4) + packet_type(1) + request_id(4) +
           handle_len(4) + offset(8) + count(4) */
        uint32_t packet_len = (uint32_t)handle->handle_len + 25;
        uint32_t request_id;

        chunk = LIBSSH2_ALLOC(session, packet_len +
                              sizeof(struct sftp_pipeline_chunk));
        if (!chunk)
            return _libssh2_error(session, LIBSSH2_ERROR_ALLOC,
                                  "malloc fail for FXP_WRITE");

        chunk->len = size;
        chunk->lefttosend = packet_len;
        chunk->sent = 0;

        s = chunk->packet;

        _libssh2_store_u32(&s, packet_len - 4);
        *s++ = SSH_FXP_READ;
        request_id = sftp->request_id++;
        chunk->request_id = request_id;
        _libssh2_store_u32(&s, request_id);
        _libssh2_store_str(&s, handle->handle, handle->handle_len);
        _libssh2_store_u64(&s, filep->offset_sent);
        filep->offset_sent += size; /* advance offset at once */
        _libssh2_store_u32(&s, size);

        /* add this new entry LAST in the list */
        _libssh2_list_add(&handle->packet_list, &chunk->node);
        count -= size; /* deduct the size we used, as we might have
                          to create more packets */
    }

    /* move through the READ packets that haven't been sent and send as many
       as possible - remember that we don't block */
    chunk = _libssh2_list_first(&handle->packet_list);

    while(chunk) {
        if(chunk->lefttosend) {
            rc = _libssh2_channel_write(channel, 0,
                                        &chunk->packet[chunk->sent],
                                        chunk->lefttosend);
            if(rc < 0) {
                if(rc != LIBSSH2_ERROR_EAGAIN)
                    /* error */
                    return rc;
                eagain++;
                break;
            }

            /* remember where to continue sending the next time */
            chunk->lefttosend -= rc;
            chunk->sent += rc;

            if(chunk->lefttosend)
                /* data left to send, get out of loop */
                break;
        }

        /* move on to the next chunk with data to send */
        chunk = _libssh2_list_next(&chunk->node);
    }

    /*
     * Count all ACKed packets and act on the contents of them.
     */
    chunk = _libssh2_list_first(&handle->packet_list);

    while(chunk) {
        unsigned char *data;
        size_t data_len;
        uint32_t rc32;
        static const unsigned char read_responses[2] = {
            SSH_FXP_DATA, SSH_FXP_STATUS
        };

        if(chunk->lefttosend)
            /* if the chunk still has data left to send, we shouldn't wait for
               an ACK for it just yet */
            break;

        rc = sftp_packet_requirev(sftp, 2, read_responses,
                                  chunk->request_id, &data, &data_len);
        if (rc == LIBSSH2_ERROR_EAGAIN) {
            eagain++;
            break;
        }
        else if (rc)
            return _libssh2_error(session, rc,
                                  "Error waiting for FXP_READ ACK");

        /*
         * We get DATA or STATUS back. STATUS can be error, or it is FX_EOF
         * when we reach the end of the file.
         */

        switch (data[0]) {
        case SSH_FXP_STATUS:
            /* we must remove all outstanding READ requests, as either we got
               an error or we're at end of file */
            sftp_packetlist_flush(handle);

            rc32 = _libssh2_ntohu32(data + 5);
            LIBSSH2_FREE(session, data);

            if (rc32 == LIBSSH2_FX_EOF) {
                filep->eof = TRUE;
                return total_read;
            }
            else {
                sftp->last_errno = rc32;
                return _libssh2_error(session, LIBSSH2_ERROR_SFTP_PROTOCOL,
                                      "SFTP READ error");
            }
            break;

        case SSH_FXP_DATA:
            rc32 = _libssh2_ntohu32(data + 5);
            if (rc32 > (data_len - 9))
                return _libssh2_error(session, LIBSSH2_ERROR_SFTP_PROTOCOL,
                                      "SFTP Protocol badness");

            if(rc32 != chunk->len)
                /* a short read means this is the last read in the file */
                filep->eof = TRUE;

            if(total_read + rc32 > buffer_size) {
                /* figure out the overlap amount */
                filep->data_left = (total_read + rc32) - buffer_size;

                /* getting the full packet would overflow the buffer, so
                   only get the correct amount and keep the remainder */
                rc32 = (uint32_t)(buffer_size - total_read);

                /* store data to keep for next call */
                filep->data = data;
                filep->data_len = data_len;
            }
            else
                filep->data_len = 0;

            /* copy the received data from the received FXP_DATA packet to the
               buffer at the correct index */
            memcpy(buffer + total_read, data + 9, rc32);
            filep->offset += rc32;
            total_read += rc32;

            if(!filep->data_len)
                /* free the allocated data if not stored to keep */
                LIBSSH2_FREE(session, data);
            else {
                /* force the loop to end since the receive buffer is full
                   already, but remove this chunk from the list first */
                _libssh2_list_remove(&chunk->node); /* remove from list */
                LIBSSH2_FREE(session, chunk); /* free memory */

                chunk = NULL;
                continue;
            }
            break;
        }

        next = _libssh2_list_next(&chunk->node);

        _libssh2_list_remove(&chunk->node); /* remove from list */
        LIBSSH2_FREE(session, chunk); /* free memory */

        chunk = next;
    }

    if(total_read)
        return total_read;
    else if(eagain)
        return _libssh2_error(session, LIBSSH2_ERROR_EAGAIN,
                              "Would block sftp_read");
    return 0;
}

/* libssh2_sftp_read
 * Read from an SFTP file handle
 */
LIBSSH2_API ssize_t
libssh2_sftp_read(LIBSSH2_SFTP_HANDLE *hnd, char *buffer,
                  size_t buffer_maxlen)
{
    ssize_t rc;
    if(!hnd)
        return LIBSSH2_ERROR_BAD_USE;
    BLOCK_ADJUST(rc, hnd->sftp->channel->session,
                 sftp_read(hnd, buffer, buffer_maxlen));
    return rc;
}

/* sftp_readdir
 * Read from an SFTP directory handle
 */
static ssize_t sftp_readdir(LIBSSH2_SFTP_HANDLE *handle, char *buffer,
                            size_t buffer_maxlen, char *longentry,
                            size_t longentry_maxlen,
                            LIBSSH2_SFTP_ATTRIBUTES *attrs)
{
    LIBSSH2_SFTP *sftp = handle->sftp;
    LIBSSH2_CHANNEL *channel = sftp->channel;
    LIBSSH2_SESSION *session = channel->session;
    size_t data_len;
    uint32_t num_names;
    /* 13 = packet_len(4) + packet_type(1) + request_id(4) + handle_len(4) */
    uint32_t packet_len = handle->handle_len + 13;
    unsigned char *s, *data;
    static const unsigned char read_responses[2] = {
        SSH_FXP_NAME, SSH_FXP_STATUS };
    ssize_t retcode;

    if (sftp->readdir_state == libssh2_NB_state_idle) {
        if (handle->u.dir.names_left) {
            /*
             * A prior request returned more than one directory entry,
             * feed it back from the buffer
             */
            LIBSSH2_SFTP_ATTRIBUTES attrs_dummy;
            size_t real_longentry_len;
            size_t real_filename_len;
            size_t filename_len;
            size_t longentry_len;

            s = (unsigned char *) handle->u.dir.next_name;
            real_filename_len = _libssh2_ntohu32(s);

            s += 4;

            filename_len = real_filename_len;
            if (filename_len >= buffer_maxlen) {
                filename_len = LIBSSH2_ERROR_BUFFER_TOO_SMALL;
                goto end;
            }

            memcpy(buffer, s, filename_len);
            buffer[filename_len] = '\0';           /* zero terminate */
            s += real_filename_len;

            real_longentry_len = _libssh2_ntohu32(s);
            s += 4;

            if (longentry && (longentry_maxlen>1)) {
                longentry_len = real_longentry_len;

                if (longentry_len >= longentry_maxlen) {
                    filename_len = LIBSSH2_ERROR_BUFFER_TOO_SMALL;
                    goto end;
                }

                memcpy(longentry, s, longentry_len);
                longentry[longentry_len] = '\0'; /* zero terminate */
            }
            s += real_longentry_len;

            if (attrs)
                memset(attrs, 0, sizeof(LIBSSH2_SFTP_ATTRIBUTES));

            s += sftp_bin2attr(attrs ? attrs : &attrs_dummy, s);

            handle->u.dir.next_name = (char *) s;
          end:

            if ((--handle->u.dir.names_left) == 0)
                LIBSSH2_FREE(session, handle->u.dir.names_packet);

            _libssh2_debug(session, LIBSSH2_TRACE_SFTP,
                           "libssh2_sftp_readdir_ex() return %d",
                           filename_len);
            return (ssize_t)filename_len;
        }

        /* Request another entry(entries?) */

        s = sftp->readdir_packet = LIBSSH2_ALLOC(session, packet_len);
        if (!sftp->readdir_packet)
            return _libssh2_error(session, LIBSSH2_ERROR_ALLOC,
                                  "Unable to allocate memory for "
                                  "FXP_READDIR packet");

        _libssh2_store_u32(&s, packet_len - 4);
        *(s++) = SSH_FXP_READDIR;
        sftp->readdir_request_id = sftp->request_id++;
        _libssh2_store_u32(&s, sftp->readdir_request_id);
        _libssh2_store_str(&s, handle->handle, handle->handle_len);

        sftp->readdir_state = libssh2_NB_state_created;
    }

    if (sftp->readdir_state == libssh2_NB_state_created) {
        _libssh2_debug(session, LIBSSH2_TRACE_SFTP,
                       "Reading entries from directory handle");
        retcode = _libssh2_channel_write(channel, 0, sftp->readdir_packet,
                                         packet_len);
        if (retcode == LIBSSH2_ERROR_EAGAIN) {
            return retcode;
        }
        else if ((ssize_t)packet_len != retcode) {
            LIBSSH2_FREE(session, sftp->readdir_packet);
            sftp->readdir_packet = NULL;
            sftp->readdir_state = libssh2_NB_state_idle;
            return _libssh2_error(session, LIBSSH2_ERROR_SOCKET_SEND,
                                  "_libssh2_channel_write() failed");
        }

        LIBSSH2_FREE(session, sftp->readdir_packet);
        sftp->readdir_packet = NULL;

        sftp->readdir_state = libssh2_NB_state_sent;
    }

    retcode = sftp_packet_requirev(sftp, 2, read_responses,
                                   sftp->readdir_request_id, &data,
                                   &data_len);
    if (retcode == LIBSSH2_ERROR_EAGAIN)
        return retcode;
    else if (retcode) {
        sftp->readdir_state = libssh2_NB_state_idle;
        return _libssh2_error(session, LIBSSH2_ERROR_SOCKET_TIMEOUT,
                              "Timeout waiting for status message");
    }

    if (data[0] == SSH_FXP_STATUS) {
        retcode = _libssh2_ntohu32(data + 5);
        LIBSSH2_FREE(session, data);
        if (retcode == LIBSSH2_FX_EOF) {
            sftp->readdir_state = libssh2_NB_state_idle;
            return 0;
        }
        else {
            sftp->last_errno = retcode;
            sftp->readdir_state = libssh2_NB_state_idle;
            return _libssh2_error(session, LIBSSH2_ERROR_SFTP_PROTOCOL,
                                  "SFTP Protocol Error");
        }
    }

    sftp->readdir_state = libssh2_NB_state_idle;

    num_names = _libssh2_ntohu32(data + 5);
    _libssh2_debug(session, LIBSSH2_TRACE_SFTP, "%lu entries returned",
                   num_names);
    if (!num_names) {
        LIBSSH2_FREE(session, data);
        return 0;
    }

    handle->u.dir.names_left = num_names;
    handle->u.dir.names_packet = data;
    handle->u.dir.next_name = (char *) data + 9;

    /* use the name popping mechanism from the start of the function */
    return sftp_readdir(handle, buffer, buffer_maxlen, longentry,
                        longentry_maxlen, attrs);
}

/* libssh2_sftp_readdir_ex
 * Read from an SFTP directory handle
 */
LIBSSH2_API int
libssh2_sftp_readdir_ex(LIBSSH2_SFTP_HANDLE *hnd, char *buffer,
                        size_t buffer_maxlen, char *longentry,
                        size_t longentry_maxlen,
                        LIBSSH2_SFTP_ATTRIBUTES *attrs)
{
    int rc;
    if(!hnd)
        return LIBSSH2_ERROR_BAD_USE;
    BLOCK_ADJUST(rc, hnd->sftp->channel->session,
                 sftp_readdir(hnd, buffer, buffer_maxlen, longentry,
                              longentry_maxlen, attrs));
    return rc;
}

/*
 * sftp_write
 *
 * Write data to an SFTP handle. Returns the number of bytes written, or
 * a negative error code.
 *
 * We recommend sending very large data buffers to this function!
 *
 * Concept:
 *
 * - Detect how much of the given buffer that was already sent in a previous
 *   call by inspecting the linked list of outgoing chunks. Make sure to skip
 *   passed the data that has already been taken care of.
 *
 * - Split all (new) outgoing data in chunks no larger than N.
 *
 * - Each N bytes chunk gets created as a separate SFTP packet.
 *
 * - Add all created outgoing packets to the linked list.
 *
 * - Walk through the list and send the chunks that haven't been sent,
 *   as many as possible until EAGAIN. Some of the chunks may have been put
 *   in the list in a previous invoke.
 *
 * - For all the chunks in the list that have been completely sent off, check
 *   for ACKs. If a chunk has been ACKed, it is removed from the linked
 *   list and the "acked" counter gets increased with that data amount.
 *
 * - Return TOTAL bytes acked so far.
 *
 * Caveats:
 * -  be careful: we must not return a higher number than what was given!
 *
 * TODO:
 *   Introduce an option that disables this sort of "speculative" ahead writing
 *   as there's a risk that it will do harm to some app.
 */

static ssize_t sftp_write(LIBSSH2_SFTP_HANDLE *handle, const char *buffer,
                          size_t count)
{
    LIBSSH2_SFTP *sftp = handle->sftp;
    LIBSSH2_CHANNEL *channel = sftp->channel;
    LIBSSH2_SESSION *session = channel->session;
    size_t data_len;
    uint32_t retcode;
    uint32_t packet_len;
    unsigned char *s, *data;
    ssize_t rc;
    struct sftp_pipeline_chunk *chunk;
    struct sftp_pipeline_chunk *next;
    size_t acked = 0;
    size_t org_count = count;
    size_t eagain = 0;

    /* Number of bytes sent off that haven't been acked and therefor we will
       get passed in here again.

       Also, add up the number of bytes that actually already have been acked
       but we haven't been able to return as such yet, so we will get that
       data as well passed in here again.
    */
    size_t already = (handle->u.file.offset_sent - handle->u.file.offset)+
        handle->u.file.acked;

    if(count >= already) {
        /* skip the part already made into packets */
        buffer += already;
        count -= already;
    }
    else
        /* there is more data already fine than what we got in this call */
        count = 0;

    while(count) {
        /* TODO: Possibly this should have some logic to prevent a very very
           small fraction to be left but lets ignore that for now */
        uint32_t size = MIN(MAX_SFTP_OUTGOING_SIZE, count);
        uint32_t request_id;

        /* 25 = packet_len(4) + packet_type(1) + request_id(4) +
           handle_len(4) + offset(8) + count(4) */
        packet_len = handle->handle_len + size + 25;

        chunk = LIBSSH2_ALLOC(session, packet_len +
                              sizeof(struct sftp_pipeline_chunk));
        if (!chunk)
            return _libssh2_error(session, LIBSSH2_ERROR_ALLOC,
                                  "malloc fail for FXP_WRITE");

        chunk->len = size;
        chunk->sent = 0;
        chunk->lefttosend = packet_len;

        s = chunk->packet;
        _libssh2_store_u32(&s, packet_len - 4);

        *(s++) = SSH_FXP_WRITE;
        request_id = sftp->request_id++;
        chunk->request_id = request_id;
        _libssh2_store_u32(&s, request_id);
        _libssh2_store_str(&s, handle->handle, handle->handle_len);
        _libssh2_store_u64(&s, handle->u.file.offset_sent);
        handle->u.file.offset_sent += size; /* advance offset at once */
        _libssh2_store_str(&s, buffer, size);

        /* add this new entry LAST in the list */
        _libssh2_list_add(&handle->packet_list, &chunk->node);

        buffer += size;
        count -= size; /* deduct the size we used, as we might have
                          to create more packets */
    }

    /* move through the WRITE packets that haven't been sent and send as many
       as possible - remember that we don't block */
    chunk = _libssh2_list_first(&handle->packet_list);

    while(chunk) {
        if(chunk->lefttosend) {
            rc = _libssh2_channel_write(channel, 0,
                                        &chunk->packet[chunk->sent],
                                        chunk->lefttosend);
            if(rc < 0) {
                if(rc != LIBSSH2_ERROR_EAGAIN)
                    /* error */
                    return rc;
                eagain++;
                break;
            }

            /* remember where to continue sending the next time */
            chunk->lefttosend -= rc;
            chunk->sent += rc;

            if(chunk->lefttosend)
                /* data left to send, get out of loop */
                break;
        }

        /* move on to the next chunk with data to send */
        chunk = _libssh2_list_next(&chunk->node);
    }

    /*
     * Count all ACKed packets
     */
    chunk = _libssh2_list_first(&handle->packet_list);

    while(chunk) {
        if(chunk->lefttosend)
            /* if the chunk still has data left to send, we shouldn't wait for
               an ACK for it just yet */
            break;

        /* we check the packets in order */
        rc = sftp_packet_require(sftp, SSH_FXP_STATUS,
                                 chunk->request_id, &data, &data_len);
        if (rc == LIBSSH2_ERROR_EAGAIN) {
            eagain++;
            break;
        }
        else if (rc) {
            return _libssh2_error(session, rc, "Waiting for SFTP status");
        }
        retcode = _libssh2_ntohu32(data + 5);
        LIBSSH2_FREE(session, data);

        sftp->last_errno = retcode;
        if (retcode == LIBSSH2_FX_OK) {
            acked += chunk->len; /* number of payload data that was acked
                                    here */

            /* we increase the offset value for all acks */
            handle->u.file.offset += chunk->len;

            next = _libssh2_list_next(&chunk->node);

            _libssh2_list_remove(&chunk->node); /* remove from list */
            LIBSSH2_FREE(session, chunk); /* free memory */

            chunk = next;
        }
        else
            /* the server returned an error for that written chunk, propagate
               this back to our parent function */
            return _libssh2_error(session, LIBSSH2_ERROR_SFTP_PROTOCOL,
                                  "FXP write failed");
    }

    /* if there were acked data in a previous call that wasn't returned then,
       add that up and try to return it all now. This can happen if the app
       first sends a huge buffer of data, and then in a second call it sends a
       smaller one. */
    acked += handle->u.file.acked;

    if(acked) {
        ssize_t ret = MIN(acked, org_count);
        /* we got data acked so return that amount, but no more than what
           was asked to get sent! */

        /* store the remainder. 'ret' is always equal to or less than 'acked'
           here */
        handle->u.file.acked = acked - ret;

        return ret;
    }
    else if(eagain)
        return _libssh2_error(session, LIBSSH2_ERROR_EAGAIN,
                              "Would block sftp_write");
    else
        return 0; /* nothing was acked, and no EAGAIN was received! */
}

/* libssh2_sftp_write
 * Write data to a file handle
 */
LIBSSH2_API ssize_t
libssh2_sftp_write(LIBSSH2_SFTP_HANDLE *hnd, const char *buffer,
                   size_t count)
{
    ssize_t rc;
    if(!hnd)
        return LIBSSH2_ERROR_BAD_USE;
    BLOCK_ADJUST(rc, hnd->sftp->channel->session,
                 sftp_write(hnd, buffer, count));
    return rc;

}

/*
 * sftp_fstat
 *
 * Get or Set stat on a file
 */
static int sftp_fstat(LIBSSH2_SFTP_HANDLE *handle,
                      LIBSSH2_SFTP_ATTRIBUTES *attrs, int setstat)
{
    LIBSSH2_SFTP *sftp = handle->sftp;
    LIBSSH2_CHANNEL *channel = sftp->channel;
    LIBSSH2_SESSION *session = channel->session;
    size_t data_len;
    /* 13 = packet_len(4) + packet_type(1) + request_id(4) + handle_len(4) */
    uint32_t packet_len =
        handle->handle_len + 13 + (setstat ? sftp_attrsize(attrs->flags) : 0);
    unsigned char *s, *data;
    static const unsigned char fstat_responses[2] =
        { SSH_FXP_ATTRS, SSH_FXP_STATUS };
    ssize_t rc;

    if (sftp->fstat_state == libssh2_NB_state_idle) {
        _libssh2_debug(session, LIBSSH2_TRACE_SFTP, "Issuing %s command",
                       setstat ? "set-stat" : "stat");
        s = sftp->fstat_packet = LIBSSH2_ALLOC(session, packet_len);
        if (!sftp->fstat_packet) {
            return _libssh2_error(session, LIBSSH2_ERROR_ALLOC,
                                  "Unable to allocate memory for "
                                  "FSTAT/FSETSTAT packet");
        }

        _libssh2_store_u32(&s, packet_len - 4);
        *(s++) = setstat ? SSH_FXP_FSETSTAT : SSH_FXP_FSTAT;
        sftp->fstat_request_id = sftp->request_id++;
        _libssh2_store_u32(&s, sftp->fstat_request_id);
        _libssh2_store_str(&s, handle->handle, handle->handle_len);

        if (setstat) {
            s += sftp_attr2bin(s, attrs);
        }

        sftp->fstat_state = libssh2_NB_state_created;
    }

    if (sftp->fstat_state == libssh2_NB_state_created) {
        rc = _libssh2_channel_write(channel, 0, sftp->fstat_packet,
                                    packet_len);
        if (rc == LIBSSH2_ERROR_EAGAIN) {
            return rc;
        }
        else if ((ssize_t)packet_len != rc) {
            LIBSSH2_FREE(session, sftp->fstat_packet);
            sftp->fstat_packet = NULL;
            sftp->fstat_state = libssh2_NB_state_idle;
            return _libssh2_error(session, LIBSSH2_ERROR_SOCKET_SEND,
                                  (setstat ? "Unable to send FXP_FSETSTAT"
                                   : "Unable to send FXP_FSTAT command"));
        }
        LIBSSH2_FREE(session, sftp->fstat_packet);
        sftp->fstat_packet = NULL;

        sftp->fstat_state = libssh2_NB_state_sent;
    }

    rc = sftp_packet_requirev(sftp, 2, fstat_responses,
                              sftp->fstat_request_id, &data,
                              &data_len);
    if (rc == LIBSSH2_ERROR_EAGAIN) {
        return rc;
    } else if (rc) {
        sftp->fstat_state = libssh2_NB_state_idle;
        return _libssh2_error(session, LIBSSH2_ERROR_SOCKET_TIMEOUT,
                              "Timeout waiting for status message");
    }

    sftp->fstat_state = libssh2_NB_state_idle;

    if (data[0] == SSH_FXP_STATUS) {
        uint32_t retcode;

        retcode = _libssh2_ntohu32(data + 5);
        LIBSSH2_FREE(session, data);
        if (retcode == LIBSSH2_FX_OK) {
            return 0;
        } else {
            sftp->last_errno = retcode;
            return _libssh2_error(session, LIBSSH2_ERROR_SFTP_PROTOCOL,
                                  "SFTP Protocol Error");
        }
    }

    sftp_bin2attr(attrs, data + 5);
    LIBSSH2_FREE(session, data);

    return 0;
}

/* libssh2_sftp_fstat_ex
 * Get or Set stat on a file
 */
LIBSSH2_API int
libssh2_sftp_fstat_ex(LIBSSH2_SFTP_HANDLE *hnd,
                      LIBSSH2_SFTP_ATTRIBUTES *attrs, int setstat)
{
    int rc;
    if(!hnd || !attrs)
        return LIBSSH2_ERROR_BAD_USE;
    BLOCK_ADJUST(rc, hnd->sftp->channel->session,
                 sftp_fstat(hnd, attrs, setstat));
    return rc;
}


/* libssh2_sftp_seek64
 * Set the read/write pointer to an arbitrary position within the file
 */
LIBSSH2_API void
libssh2_sftp_seek64(LIBSSH2_SFTP_HANDLE *handle, libssh2_uint64_t offset)
{
    if(handle)
        handle->u.file.offset = handle->u.file.offset_sent = offset;
}

/* libssh2_sftp_seek
 * Set the read/write pointer to an arbitrary position within the file
 */
LIBSSH2_API void
libssh2_sftp_seek(LIBSSH2_SFTP_HANDLE *handle, size_t offset)
{
    libssh2_sftp_seek64(handle, (libssh2_uint64_t)offset);
}

/* libssh2_sftp_tell
 * Return the current read/write pointer's offset
 */
LIBSSH2_API size_t
libssh2_sftp_tell(LIBSSH2_SFTP_HANDLE *handle)
{
    if(!handle)
        return 0; /* no handle, no size */

    /* NOTE: this may very well truncate the size if it is larger than what
       size_t can hold, so libssh2_sftp_tell64() is really the function you
       should use */
    return (size_t)(handle->u.file.offset);
}

/* libssh2_sftp_tell64
 * Return the current read/write pointer's offset
 */
LIBSSH2_API libssh2_uint64_t
libssh2_sftp_tell64(LIBSSH2_SFTP_HANDLE *handle)
{
    if(!handle)
        return 0; /* no handle, no size */

    return handle->u.file.offset;
}

/*
 * Flush all remaining incoming SFTP packets.
 */
static void sftp_packet_flush(LIBSSH2_SFTP *sftp)
{
    LIBSSH2_CHANNEL *channel = sftp->channel;
    LIBSSH2_SESSION *session = channel->session;
    LIBSSH2_SFTP_PACKET *packet = _libssh2_list_first(&sftp->packets);

    while(packet) {
        LIBSSH2_SFTP_PACKET *next;

        /* check next struct in the list */
        next =  _libssh2_list_next(&packet->node);
        _libssh2_list_remove(&packet->node);
        LIBSSH2_FREE(session, packet->data);
        LIBSSH2_FREE(session, packet);

        packet = next;
    }

}

/* sftp_close_handle
 *
 * Close a file or directory handle
 * Also frees handle resource and unlinks it from the SFTP structure
 */
static int
sftp_close_handle(LIBSSH2_SFTP_HANDLE *handle)
{
    LIBSSH2_SFTP *sftp = handle->sftp;
    LIBSSH2_CHANNEL *channel = sftp->channel;
    LIBSSH2_SESSION *session = channel->session;
    size_t data_len;
    int retcode;
    /* 13 = packet_len(4) + packet_type(1) + request_id(4) + handle_len(4) */
    uint32_t packet_len = handle->handle_len + 13;
    unsigned char *s, *data = NULL;
    int rc;

    if (handle->close_state == libssh2_NB_state_idle) {
        _libssh2_debug(session, LIBSSH2_TRACE_SFTP, "Closing handle");
        s = handle->close_packet = LIBSSH2_ALLOC(session, packet_len);
        if (!handle->close_packet) {
            return _libssh2_error(session, LIBSSH2_ERROR_ALLOC,
                                  "Unable to allocate memory for FXP_CLOSE "
                                  "packet");
        }

        _libssh2_store_u32(&s, packet_len - 4);
        *(s++) = SSH_FXP_CLOSE;
        handle->close_request_id = sftp->request_id++;
        _libssh2_store_u32(&s, handle->close_request_id);
        _libssh2_store_str(&s, handle->handle, handle->handle_len);
        handle->close_state = libssh2_NB_state_created;
    }

    if (handle->close_state == libssh2_NB_state_created) {
        rc = _libssh2_channel_write(channel, 0, handle->close_packet,
                                    packet_len);
        if (rc == LIBSSH2_ERROR_EAGAIN) {
            return rc;
        } else if ((ssize_t)packet_len != rc) {
            LIBSSH2_FREE(session, handle->close_packet);
            handle->close_packet = NULL;
            handle->close_state = libssh2_NB_state_idle;
            return _libssh2_error(session, LIBSSH2_ERROR_SOCKET_SEND,
                                  "Unable to send FXP_CLOSE command");
        }
        LIBSSH2_FREE(session, handle->close_packet);
        handle->close_packet = NULL;

        handle->close_state = libssh2_NB_state_sent;
    }

    if (handle->close_state == libssh2_NB_state_sent) {
        rc = sftp_packet_require(sftp, SSH_FXP_STATUS,
                                 handle->close_request_id, &data,
                                 &data_len);
        if (rc == LIBSSH2_ERROR_EAGAIN) {
            return rc;
        } else if (rc) {
            handle->close_state = libssh2_NB_state_idle;
            return _libssh2_error(session, LIBSSH2_ERROR_SOCKET_TIMEOUT,
                                  "Timeout waiting for status message");
        }

        handle->close_state = libssh2_NB_state_sent1;
    }

    if(!data)
        /* if it reaches this point with data unset, something unwanted
           happened (like this function is called again when in
           libssh2_NB_state_sent1 state) and we just bail out */
        return LIBSSH2_ERROR_INVAL;

    retcode = _libssh2_ntohu32(data + 5);
    LIBSSH2_FREE(session, data);

    if (retcode != LIBSSH2_FX_OK) {
        sftp->last_errno = retcode;
        handle->close_state = libssh2_NB_state_idle;
        return _libssh2_error(session, LIBSSH2_ERROR_SFTP_PROTOCOL,
                              "SFTP Protocol Error");
    }

    /* remove this handle from the parent's list */
    _libssh2_list_remove(&handle->node);

    if ((handle->handle_type == LIBSSH2_SFTP_HANDLE_DIR)
        && handle->u.dir.names_left) {
        LIBSSH2_FREE(session, handle->u.dir.names_packet);
    }
    else {
        if(handle->u.file.data)
            LIBSSH2_FREE(session, handle->u.file.data);
    }

    sftp_packetlist_flush(handle);

    handle->close_state = libssh2_NB_state_idle;

    LIBSSH2_FREE(session, handle);

    return 0;
}

/* libssh2_sftp_close_handle
 *
 * Close a file or directory handle
 * Also frees handle resource and unlinks it from the SFTP structure
 */
LIBSSH2_API int
libssh2_sftp_close_handle(LIBSSH2_SFTP_HANDLE *hnd)
{
    int rc;
    if(!hnd)
        return LIBSSH2_ERROR_BAD_USE;
    BLOCK_ADJUST(rc, hnd->sftp->channel->session, sftp_close_handle(hnd));
    return rc;
}

/* sftp_unlink
 * Delete a file from the remote server
 */
static int sftp_unlink(LIBSSH2_SFTP *sftp, const char *filename,
                       size_t filename_len)
{
    LIBSSH2_CHANNEL *channel = sftp->channel;
    LIBSSH2_SESSION *session = channel->session;
    size_t data_len;
    int retcode;
    /* 13 = packet_len(4) + packet_type(1) + request_id(4) + filename_len(4) */
    uint32_t packet_len = filename_len + 13;
    unsigned char *s, *data;
    int rc;

    if (sftp->unlink_state == libssh2_NB_state_idle) {
        _libssh2_debug(session, LIBSSH2_TRACE_SFTP, "Unlinking %s", filename);
        s = sftp->unlink_packet = LIBSSH2_ALLOC(session, packet_len);
        if (!sftp->unlink_packet) {
            return _libssh2_error(session, LIBSSH2_ERROR_ALLOC,
                                  "Unable to allocate memory for FXP_REMOVE "
                                  "packet");
        }

        _libssh2_store_u32(&s, packet_len - 4);
        *(s++) = SSH_FXP_REMOVE;
        sftp->unlink_request_id = sftp->request_id++;
        _libssh2_store_u32(&s, sftp->unlink_request_id);
        _libssh2_store_str(&s, filename, filename_len);
        sftp->unlink_state = libssh2_NB_state_created;
    }

    if (sftp->unlink_state == libssh2_NB_state_created) {
        rc = _libssh2_channel_write(channel, 0, sftp->unlink_packet,
                                    packet_len);
        if (rc == LIBSSH2_ERROR_EAGAIN) {
            return rc;
        } else if ((ssize_t)packet_len != rc) {
            LIBSSH2_FREE(session, sftp->unlink_packet);
            sftp->unlink_packet = NULL;
            sftp->unlink_state = libssh2_NB_state_idle;
            return _libssh2_error(session, LIBSSH2_ERROR_SOCKET_SEND,
                                  "Unable to send FXP_REMOVE command");
        }
        LIBSSH2_FREE(session, sftp->unlink_packet);
        sftp->unlink_packet = NULL;

        sftp->unlink_state = libssh2_NB_state_sent;
    }

    rc = sftp_packet_require(sftp, SSH_FXP_STATUS,
                             sftp->unlink_request_id, &data,
                             &data_len);
    if (rc == LIBSSH2_ERROR_EAGAIN) {
        return rc;
    }
    else if (rc) {
        sftp->unlink_state = libssh2_NB_state_idle;
        return _libssh2_error(session, LIBSSH2_ERROR_SOCKET_TIMEOUT,
                              "Timeout waiting for status message");
    }

    sftp->unlink_state = libssh2_NB_state_idle;

    retcode = _libssh2_ntohu32(data + 5);
    LIBSSH2_FREE(session, data);

    if (retcode == LIBSSH2_FX_OK) {
        return 0;
    } else {
        sftp->last_errno = retcode;
        return _libssh2_error(session, LIBSSH2_ERROR_SFTP_PROTOCOL,
                              "SFTP Protocol Error");
    }
}

/* libssh2_sftp_unlink_ex
 * Delete a file from the remote server
 */
LIBSSH2_API int
libssh2_sftp_unlink_ex(LIBSSH2_SFTP *sftp, const char *filename,
                       unsigned int filename_len)
{
    int rc;
    if(!sftp)
        return LIBSSH2_ERROR_BAD_USE;
    BLOCK_ADJUST(rc, sftp->channel->session,
                 sftp_unlink(sftp, filename, filename_len));
    return rc;
}

/*
 * sftp_rename
 *
 * Rename a file on the remote server
 */
static int sftp_rename(LIBSSH2_SFTP *sftp, const char *source_filename,
                       unsigned int source_filename_len,
                       const char *dest_filename,
                       unsigned int dest_filename_len, long flags)
{
    LIBSSH2_CHANNEL *channel = sftp->channel;
    LIBSSH2_SESSION *session = channel->session;
    size_t data_len;
    int retcode;
    uint32_t packet_len =
        source_filename_len + dest_filename_len + 17 + (sftp->version >=
                                                        5 ? 4 : 0);
    /* packet_len(4) + packet_type(1) + request_id(4) +
       source_filename_len(4) + dest_filename_len(4) + flags(4){SFTP5+) */
    unsigned char *data;
    ssize_t rc;

    if (sftp->version < 2) {
        return _libssh2_error(session, LIBSSH2_ERROR_SFTP_PROTOCOL,
                              "Server does not support RENAME");
    }

    if (sftp->rename_state == libssh2_NB_state_idle) {
        _libssh2_debug(session, LIBSSH2_TRACE_SFTP, "Renaming %s to %s",
                       source_filename, dest_filename);
        sftp->rename_s = sftp->rename_packet =
            LIBSSH2_ALLOC(session, packet_len);
        if (!sftp->rename_packet) {
            return _libssh2_error(session, LIBSSH2_ERROR_ALLOC,
                                  "Unable to allocate memory for FXP_RENAME "
                                  "packet");
        }

        _libssh2_store_u32(&sftp->rename_s, packet_len - 4);
        *(sftp->rename_s++) = SSH_FXP_RENAME;
        sftp->rename_request_id = sftp->request_id++;
        _libssh2_store_u32(&sftp->rename_s, sftp->rename_request_id);
        _libssh2_store_str(&sftp->rename_s, source_filename,
                           source_filename_len);
        _libssh2_store_str(&sftp->rename_s, dest_filename, dest_filename_len);

        if (sftp->version >= 5)
            _libssh2_store_u32(&sftp->rename_s, flags);

        sftp->rename_state = libssh2_NB_state_created;
    }

    if (sftp->rename_state == libssh2_NB_state_created) {
        rc = _libssh2_channel_write(channel, 0, sftp->rename_packet,
                                    sftp->rename_s - sftp->rename_packet);
        if (rc == LIBSSH2_ERROR_EAGAIN) {
            return rc;
        } else if ((ssize_t)packet_len != rc) {
            LIBSSH2_FREE(session, sftp->rename_packet);
            sftp->rename_packet = NULL;
            sftp->rename_state = libssh2_NB_state_idle;
            return _libssh2_error(session, LIBSSH2_ERROR_SOCKET_SEND,
                                  "Unable to send FXP_RENAME command");
        }
        LIBSSH2_FREE(session, sftp->rename_packet);
        sftp->rename_packet = NULL;

        sftp->rename_state = libssh2_NB_state_sent;
    }

    rc = sftp_packet_require(sftp, SSH_FXP_STATUS,
                             sftp->rename_request_id, &data,
                             &data_len);
    if (rc == LIBSSH2_ERROR_EAGAIN) {
        return rc;
    } else if (rc) {
        sftp->rename_state = libssh2_NB_state_idle;
        return _libssh2_error(session, LIBSSH2_ERROR_SOCKET_TIMEOUT,
                              "Timeout waiting for status message");
    }

    sftp->rename_state = libssh2_NB_state_idle;

    retcode = _libssh2_ntohu32(data + 5);
    LIBSSH2_FREE(session, data);

    sftp->last_errno = retcode;

    /* now convert the SFTP error code to libssh2 return code or error
       message */
    switch (retcode) {
    case LIBSSH2_FX_OK:
        retcode = LIBSSH2_ERROR_NONE;
        break;

    case LIBSSH2_FX_FILE_ALREADY_EXISTS:
        retcode = _libssh2_error(session, LIBSSH2_ERROR_SFTP_PROTOCOL,
                                 "File already exists and "
                                 "SSH_FXP_RENAME_OVERWRITE not specified");
        break;

    case LIBSSH2_FX_OP_UNSUPPORTED:
        retcode = _libssh2_error(session, LIBSSH2_ERROR_SFTP_PROTOCOL,
                                 "Operation Not Supported");
        break;

    default:
        retcode = _libssh2_error(session, LIBSSH2_ERROR_SFTP_PROTOCOL,
                                 "SFTP Protocol Error");
        break;
    }

    return retcode;
}

/* libssh2_sftp_rename_ex
 * Rename a file on the remote server
 */
LIBSSH2_API int
libssh2_sftp_rename_ex(LIBSSH2_SFTP *sftp, const char *source_filename,
                       unsigned int source_filename_len,
                       const char *dest_filename,
                       unsigned int dest_filename_len, long flags)
{
    int rc;
    if(!sftp)
        return LIBSSH2_ERROR_BAD_USE;
    BLOCK_ADJUST(rc, sftp->channel->session,
                 sftp_rename(sftp, source_filename, source_filename_len,
                             dest_filename, dest_filename_len, flags));
    return rc;
}

/*
 * sftp_fstatvfs
 *
 * Get file system statistics
 */
static int sftp_fstatvfs(LIBSSH2_SFTP_HANDLE *handle, LIBSSH2_SFTP_STATVFS *st)
{
    LIBSSH2_SFTP *sftp = handle->sftp;
    LIBSSH2_CHANNEL *channel = sftp->channel;
    LIBSSH2_SESSION *session = channel->session;
    size_t data_len;
    /* 17 = packet_len(4) + packet_type(1) + request_id(4) + ext_len(4)
          + handle_len (4) */
    /* 20 = strlen ("fstatvfs@openssh.com") */
    uint32_t packet_len = handle->handle_len + 20 + 17;
    unsigned char *packet, *s, *data;
    ssize_t rc;
    unsigned int flag;

    if (sftp->fstatvfs_state == libssh2_NB_state_idle) {
        _libssh2_debug(session, LIBSSH2_TRACE_SFTP,
                       "Getting file system statistics");
        s = packet = LIBSSH2_ALLOC(session, packet_len);
        if (!packet) {
            return _libssh2_error(session, LIBSSH2_ERROR_ALLOC,
                                  "Unable to allocate memory for FXP_EXTENDED "
                                  "packet");
        }

        _libssh2_store_u32(&s, packet_len - 4);
        *(s++) = SSH_FXP_EXTENDED;
        sftp->fstatvfs_request_id = sftp->request_id++;
        _libssh2_store_u32(&s, sftp->fstatvfs_request_id);
        _libssh2_store_str(&s, "fstatvfs@openssh.com", 20);
        _libssh2_store_str(&s, handle->handle, handle->handle_len);

        sftp->fstatvfs_state = libssh2_NB_state_created;
    }
    else {
        packet = sftp->fstatvfs_packet;
    }

    if (sftp->fstatvfs_state == libssh2_NB_state_created) {
        rc = _libssh2_channel_write(channel, 0, packet, packet_len);
        if (rc == LIBSSH2_ERROR_EAGAIN ||
            (0 <= rc && rc < (ssize_t)packet_len)) {
            sftp->fstatvfs_packet = packet;
            return LIBSSH2_ERROR_EAGAIN;
        }

        LIBSSH2_FREE(session, packet);
        sftp->fstatvfs_packet = NULL;

        if (rc < 0) {
            sftp->fstatvfs_state = libssh2_NB_state_idle;
            return _libssh2_error(session, LIBSSH2_ERROR_SOCKET_SEND,
                                  "_libssh2_channel_write() failed");
        }
        sftp->fstatvfs_state = libssh2_NB_state_sent;
    }

    rc = sftp_packet_require(sftp, SSH_FXP_EXTENDED_REPLY,
                             sftp->fstatvfs_request_id, &data, &data_len);
    if (rc == LIBSSH2_ERROR_EAGAIN) {
        return rc;
    } else if (rc) {
        sftp->fstatvfs_state = libssh2_NB_state_idle;
        return _libssh2_error(session, LIBSSH2_ERROR_SOCKET_TIMEOUT,
                              "Timeout waiting for status message");
    } else if (data_len < 93) {
        LIBSSH2_FREE(session, data);
        sftp->fstatvfs_state = libssh2_NB_state_idle;
        return _libssh2_error(session, LIBSSH2_ERROR_SFTP_PROTOCOL,
                              "SFTP Protocol Error: short response");
    }

    sftp->fstatvfs_state = libssh2_NB_state_idle;

    st->f_bsize = _libssh2_ntohu64(data + 5);
    st->f_frsize = _libssh2_ntohu64(data + 13);
    st->f_blocks = _libssh2_ntohu64(data + 21);
    st->f_bfree = _libssh2_ntohu64(data + 29);
    st->f_bavail = _libssh2_ntohu64(data + 37);
    st->f_files = _libssh2_ntohu64(data + 45);
    st->f_ffree = _libssh2_ntohu64(data + 53);
    st->f_favail = _libssh2_ntohu64(data + 61);
    st->f_fsid = _libssh2_ntohu64(data + 69);
    flag = _libssh2_ntohu64(data + 77);
    st->f_namemax = _libssh2_ntohu64(data + 85);

    st->f_flag = (flag & SSH_FXE_STATVFS_ST_RDONLY)
                  ? LIBSSH2_SFTP_ST_RDONLY : 0;
    st->f_flag |= (flag & SSH_FXE_STATVFS_ST_NOSUID)
                  ? LIBSSH2_SFTP_ST_NOSUID : 0;

    LIBSSH2_FREE(session, data);
    return 0;
}

/* libssh2_sftp_fstatvfs
 * Get filesystem space and inode utilization (requires fstatvfs@openssh.com
 * support on the server)
 */
LIBSSH2_API int
libssh2_sftp_fstatvfs(LIBSSH2_SFTP_HANDLE *handle, LIBSSH2_SFTP_STATVFS *st)
{
    int rc;
    if(!handle || !st)
        return LIBSSH2_ERROR_BAD_USE;
    BLOCK_ADJUST(rc, handle->sftp->channel->session, sftp_fstatvfs(handle, st));
    return rc;
}

/*
 * sftp_statvfs
 *
 * Get file system statistics
 */
static int sftp_statvfs(LIBSSH2_SFTP *sftp, const char *path,
                        unsigned int path_len, LIBSSH2_SFTP_STATVFS *st)
{
    LIBSSH2_CHANNEL *channel = sftp->channel;
    LIBSSH2_SESSION *session = channel->session;
    size_t data_len;
    /* 17 = packet_len(4) + packet_type(1) + request_id(4) + ext_len(4)
          + path_len (4) */
    /* 19 = strlen ("statvfs@openssh.com") */
    uint32_t packet_len = path_len + 19 + 17;
    unsigned char *packet, *s, *data;
    ssize_t rc;
    unsigned int flag;

    if (sftp->statvfs_state == libssh2_NB_state_idle) {
        _libssh2_debug(session, LIBSSH2_TRACE_SFTP,
                       "Getting file system statistics of %s", path);
        s = packet = LIBSSH2_ALLOC(session, packet_len);
        if (!packet) {
            return _libssh2_error(session, LIBSSH2_ERROR_ALLOC,
                                  "Unable to allocate memory for FXP_EXTENDED "
                                  "packet");
        }

        _libssh2_store_u32(&s, packet_len - 4);
        *(s++) = SSH_FXP_EXTENDED;
        sftp->statvfs_request_id = sftp->request_id++;
        _libssh2_store_u32(&s, sftp->statvfs_request_id);
        _libssh2_store_str(&s, "statvfs@openssh.com", 19);
        _libssh2_store_str(&s, path, path_len);

        sftp->statvfs_state = libssh2_NB_state_created;
    }
    else {
        packet = sftp->statvfs_packet;
    }

    if (sftp->statvfs_state == libssh2_NB_state_created) {
        rc = _libssh2_channel_write(channel, 0, packet, packet_len);
        if (rc == LIBSSH2_ERROR_EAGAIN ||
            (0 <= rc && rc < (ssize_t)packet_len)) {
            sftp->statvfs_packet = packet;
            return LIBSSH2_ERROR_EAGAIN;
        }

        LIBSSH2_FREE(session, packet);
        sftp->statvfs_packet = NULL;

        if (rc < 0) {
            sftp->statvfs_state = libssh2_NB_state_idle;
            return _libssh2_error(session, LIBSSH2_ERROR_SOCKET_SEND,
                                  "_libssh2_channel_write() failed");
        }
        sftp->statvfs_state = libssh2_NB_state_sent;
    }

    rc = sftp_packet_require(sftp, SSH_FXP_EXTENDED_REPLY,
                             sftp->statvfs_request_id, &data, &data_len);
    if (rc == LIBSSH2_ERROR_EAGAIN) {
        return rc;
    } else if (rc) {
        sftp->statvfs_state = libssh2_NB_state_idle;
        return _libssh2_error(session, LIBSSH2_ERROR_SOCKET_TIMEOUT,
                              "Timeout waiting for status message");
    } else if (data_len < 93) {
        LIBSSH2_FREE(session, data);
        sftp->fstatvfs_state = libssh2_NB_state_idle;
        return _libssh2_error(session, LIBSSH2_ERROR_SFTP_PROTOCOL,
                              "SFTP Protocol Error: short response");
    }

    sftp->statvfs_state = libssh2_NB_state_idle;

    st->f_bsize = _libssh2_ntohu64(data + 5);
    st->f_frsize = _libssh2_ntohu64(data + 13);
    st->f_blocks = _libssh2_ntohu64(data + 21);
    st->f_bfree = _libssh2_ntohu64(data + 29);
    st->f_bavail = _libssh2_ntohu64(data + 37);
    st->f_files = _libssh2_ntohu64(data + 45);
    st->f_ffree = _libssh2_ntohu64(data + 53);
    st->f_favail = _libssh2_ntohu64(data + 61);
    st->f_fsid = _libssh2_ntohu64(data + 69);
    flag = _libssh2_ntohu64(data + 77);
    st->f_namemax = _libssh2_ntohu64(data + 85);

    st->f_flag = (flag & SSH_FXE_STATVFS_ST_RDONLY)
                  ? LIBSSH2_SFTP_ST_RDONLY : 0;
    st->f_flag |= (flag & SSH_FXE_STATVFS_ST_NOSUID)
                  ? LIBSSH2_SFTP_ST_NOSUID : 0;

    LIBSSH2_FREE(session, data);
    return 0;
}

/* libssh2_sftp_statvfs_ex
 * Get filesystem space and inode utilization (requires statvfs@openssh.com
 * support on the server)
 */
LIBSSH2_API int
libssh2_sftp_statvfs(LIBSSH2_SFTP *sftp, const char *path,
                     size_t path_len, LIBSSH2_SFTP_STATVFS *st)
{
    int rc;
    if(!sftp || !st)
        return LIBSSH2_ERROR_BAD_USE;
    BLOCK_ADJUST(rc, sftp->channel->session, sftp_statvfs(sftp, path, path_len,
                                                          st));
    return rc;
}


/*
 * sftp_mkdir
 *
 * Create an SFTP directory
 */
static int sftp_mkdir(LIBSSH2_SFTP *sftp, const char *path,
                      unsigned int path_len, long mode)
{
    LIBSSH2_CHANNEL *channel = sftp->channel;
    LIBSSH2_SESSION *session = channel->session;
    LIBSSH2_SFTP_ATTRIBUTES attrs = {
        LIBSSH2_SFTP_ATTR_PERMISSIONS, 0, 0, 0, 0, 0, 0
    };
    size_t data_len;
    int retcode;
    /* 13 = packet_len(4) + packet_type(1) + request_id(4) + path_len(4) */
    ssize_t packet_len = path_len + 13 +
        sftp_attrsize(LIBSSH2_SFTP_ATTR_PERMISSIONS);
    unsigned char *packet, *s, *data;
    int rc;

    if (sftp->mkdir_state == libssh2_NB_state_idle) {
        _libssh2_debug(session, LIBSSH2_TRACE_SFTP,
                       "Creating directory %s with mode 0%lo", path, mode);
        s = packet = LIBSSH2_ALLOC(session, packet_len);
        if (!packet) {
            return _libssh2_error(session, LIBSSH2_ERROR_ALLOC,
                                  "Unable to allocate memory for FXP_MKDIR "
                                  "packet");
        }
        /* Filetype in SFTP 3 and earlier */
        attrs.permissions = mode | LIBSSH2_SFTP_ATTR_PFILETYPE_DIR;

        _libssh2_store_u32(&s, packet_len - 4);
        *(s++) = SSH_FXP_MKDIR;
        sftp->mkdir_request_id = sftp->request_id++;
        _libssh2_store_u32(&s, sftp->mkdir_request_id);
        _libssh2_store_str(&s, path, path_len);

        s += sftp_attr2bin(s, &attrs);

        sftp->mkdir_state = libssh2_NB_state_created;
    }
    else {
        packet = sftp->mkdir_packet;
    }

    if (sftp->mkdir_state == libssh2_NB_state_created) {
        rc = _libssh2_channel_write(channel, 0, packet, packet_len);
        if (rc == LIBSSH2_ERROR_EAGAIN) {
            sftp->mkdir_packet = packet;
            return rc;
        }
        if (packet_len != rc) {
            LIBSSH2_FREE(session, packet);
            sftp->mkdir_state = libssh2_NB_state_idle;
            return _libssh2_error(session, LIBSSH2_ERROR_SOCKET_SEND,
                                  "_libssh2_channel_write() failed");
        }
        LIBSSH2_FREE(session, packet);
        sftp->mkdir_state = libssh2_NB_state_sent;
        sftp->mkdir_packet = NULL;
    }

    rc = sftp_packet_require(sftp, SSH_FXP_STATUS, sftp->mkdir_request_id,
                             &data, &data_len);
    if (rc == LIBSSH2_ERROR_EAGAIN) {
        return rc;
    } else if (rc) {
        sftp->mkdir_state = libssh2_NB_state_idle;
        return _libssh2_error(session, LIBSSH2_ERROR_SOCKET_TIMEOUT,
                              "Timeout waiting for status message");
    }

    sftp->mkdir_state = libssh2_NB_state_idle;

    retcode = _libssh2_ntohu32(data + 5);
    LIBSSH2_FREE(session, data);

    if (retcode == LIBSSH2_FX_OK) {
        _libssh2_debug(session, LIBSSH2_TRACE_SFTP, "OK!");
        return 0;
    } else {
        sftp->last_errno = retcode;
        return _libssh2_error(session, LIBSSH2_ERROR_SFTP_PROTOCOL,
                              "SFTP Protocol Error");
    }
}

/*
 * libssh2_sftp_mkdir_ex
 *
 * Create an SFTP directory
 */
LIBSSH2_API int
libssh2_sftp_mkdir_ex(LIBSSH2_SFTP *sftp, const char *path,
                      unsigned int path_len, long mode)
{
    int rc;
    if(!sftp)
        return LIBSSH2_ERROR_BAD_USE;
    BLOCK_ADJUST(rc, sftp->channel->session,
                 sftp_mkdir(sftp, path, path_len, mode));
    return rc;
}

/* sftp_rmdir
 * Remove a directory
 */
static int sftp_rmdir(LIBSSH2_SFTP *sftp, const char *path,
                      unsigned int path_len)
{
    LIBSSH2_CHANNEL *channel = sftp->channel;
    LIBSSH2_SESSION *session = channel->session;
    size_t data_len;
    int retcode;
    /* 13 = packet_len(4) + packet_type(1) + request_id(4) + path_len(4) */
    ssize_t packet_len = path_len + 13;
    unsigned char *s, *data;
    int rc;

    if (sftp->rmdir_state == libssh2_NB_state_idle) {
        _libssh2_debug(session, LIBSSH2_TRACE_SFTP, "Removing directory: %s",
                       path);
        s = sftp->rmdir_packet = LIBSSH2_ALLOC(session, packet_len);
        if (!sftp->rmdir_packet) {
            return _libssh2_error(session, LIBSSH2_ERROR_ALLOC,
                                  "Unable to allocate memory for FXP_RMDIR "
                                  "packet");
        }

        _libssh2_store_u32(&s, packet_len - 4);
        *(s++) = SSH_FXP_RMDIR;
        sftp->rmdir_request_id = sftp->request_id++;
        _libssh2_store_u32(&s, sftp->rmdir_request_id);
        _libssh2_store_str(&s, path, path_len);

        sftp->rmdir_state = libssh2_NB_state_created;
    }

    if (sftp->rmdir_state == libssh2_NB_state_created) {
        rc = _libssh2_channel_write(channel, 0, sftp->rmdir_packet,
                                    packet_len);
        if (rc == LIBSSH2_ERROR_EAGAIN) {
            return rc;
        } else if (packet_len != rc) {
            LIBSSH2_FREE(session, sftp->rmdir_packet);
            sftp->rmdir_packet = NULL;
            sftp->rmdir_state = libssh2_NB_state_idle;
            return _libssh2_error(session, LIBSSH2_ERROR_SOCKET_SEND,
                                  "Unable to send FXP_RMDIR command");
        }
        LIBSSH2_FREE(session, sftp->rmdir_packet);
        sftp->rmdir_packet = NULL;

        sftp->rmdir_state = libssh2_NB_state_sent;
    }

    rc = sftp_packet_require(sftp, SSH_FXP_STATUS,
                             sftp->rmdir_request_id, &data, &data_len);
    if (rc == LIBSSH2_ERROR_EAGAIN) {
        return rc;
    } else if (rc) {
        sftp->rmdir_state = libssh2_NB_state_idle;
        return _libssh2_error(session, LIBSSH2_ERROR_SOCKET_TIMEOUT,
                              "Timeout waiting for status message");
    }

    sftp->rmdir_state = libssh2_NB_state_idle;

    retcode = _libssh2_ntohu32(data + 5);
    LIBSSH2_FREE(session, data);

    if (retcode == LIBSSH2_FX_OK) {
        return 0;
    } else {
        sftp->last_errno = retcode;
        return _libssh2_error(session, LIBSSH2_ERROR_SFTP_PROTOCOL,
                              "SFTP Protocol Error");
    }
}

/* libssh2_sftp_rmdir_ex
 * Remove a directory
 */
LIBSSH2_API int
libssh2_sftp_rmdir_ex(LIBSSH2_SFTP *sftp, const char *path,
                      unsigned int path_len)
{
    int rc;
    if(!sftp)
        return LIBSSH2_ERROR_BAD_USE;
    BLOCK_ADJUST(rc, sftp->channel->session,
                 sftp_rmdir(sftp, path, path_len));
    return rc;
}

/* sftp_stat
 * Stat a file or symbolic link
 */
static int sftp_stat(LIBSSH2_SFTP *sftp, const char *path,
                     unsigned int path_len, int stat_type,
                     LIBSSH2_SFTP_ATTRIBUTES * attrs)
{
    LIBSSH2_CHANNEL *channel = sftp->channel;
    LIBSSH2_SESSION *session = channel->session;
    size_t data_len;
    /* 13 = packet_len(4) + packet_type(1) + request_id(4) + path_len(4) */
    ssize_t packet_len =
        path_len + 13 +
        ((stat_type ==
          LIBSSH2_SFTP_SETSTAT) ? sftp_attrsize(attrs->flags) : 0);
    unsigned char *s, *data;
    static const unsigned char stat_responses[2] =
        { SSH_FXP_ATTRS, SSH_FXP_STATUS };
    int rc;

    if (sftp->stat_state == libssh2_NB_state_idle) {
        _libssh2_debug(session, LIBSSH2_TRACE_SFTP, "%s %s",
                       (stat_type == LIBSSH2_SFTP_SETSTAT) ? "Set-statting" :
                       (stat_type ==
                        LIBSSH2_SFTP_LSTAT ? "LStatting" : "Statting"), path);
        s = sftp->stat_packet = LIBSSH2_ALLOC(session, packet_len);
        if (!sftp->stat_packet) {
            return _libssh2_error(session, LIBSSH2_ERROR_ALLOC,
                                  "Unable to allocate memory for FXP_*STAT "
                                  "packet");
        }

        _libssh2_store_u32(&s, packet_len - 4);

        switch (stat_type) {
        case LIBSSH2_SFTP_SETSTAT:
            *(s++) = SSH_FXP_SETSTAT;
            break;

        case LIBSSH2_SFTP_LSTAT:
            *(s++) = SSH_FXP_LSTAT;
            break;

        case LIBSSH2_SFTP_STAT:
        default:
            *(s++) = SSH_FXP_STAT;
        }
        sftp->stat_request_id = sftp->request_id++;
        _libssh2_store_u32(&s, sftp->stat_request_id);
        _libssh2_store_str(&s, path, path_len);

        if (stat_type == LIBSSH2_SFTP_SETSTAT)
            s += sftp_attr2bin(s, attrs);

        sftp->stat_state = libssh2_NB_state_created;
    }

    if (sftp->stat_state == libssh2_NB_state_created) {
        rc = _libssh2_channel_write(channel, 0, sftp->stat_packet, packet_len);
        if (rc == LIBSSH2_ERROR_EAGAIN) {
            return rc;
        } else if (packet_len != rc) {
            LIBSSH2_FREE(session, sftp->stat_packet);
            sftp->stat_packet = NULL;
            sftp->stat_state = libssh2_NB_state_idle;
            return _libssh2_error(session, LIBSSH2_ERROR_SOCKET_SEND,
                                  "Unable to send STAT/LSTAT/SETSTAT command");
        }
        LIBSSH2_FREE(session, sftp->stat_packet);
        sftp->stat_packet = NULL;

        sftp->stat_state = libssh2_NB_state_sent;
    }

    rc = sftp_packet_requirev(sftp, 2, stat_responses,
                              sftp->stat_request_id, &data, &data_len);
    if (rc == LIBSSH2_ERROR_EAGAIN) {
        return rc;
    } else if (rc) {
        sftp->stat_state = libssh2_NB_state_idle;
        return _libssh2_error(session, LIBSSH2_ERROR_SOCKET_TIMEOUT,
                              "Timeout waiting for status message");
    }

    sftp->stat_state = libssh2_NB_state_idle;

    if (data[0] == SSH_FXP_STATUS) {
        int retcode;

        retcode = _libssh2_ntohu32(data + 5);
        LIBSSH2_FREE(session, data);
        if (retcode == LIBSSH2_FX_OK) {
            return 0;
        } else {
            sftp->last_errno = retcode;
            return _libssh2_error(session, LIBSSH2_ERROR_SFTP_PROTOCOL,
                                  "SFTP Protocol Error");
        }
    }

    memset(attrs, 0, sizeof(LIBSSH2_SFTP_ATTRIBUTES));
    sftp_bin2attr(attrs, data + 5);
    LIBSSH2_FREE(session, data);

    return 0;
}

/* libssh2_sftp_stat_ex
 * Stat a file or symbolic link
 */
LIBSSH2_API int
libssh2_sftp_stat_ex(LIBSSH2_SFTP *sftp, const char *path,
                     unsigned int path_len, int stat_type,
                     LIBSSH2_SFTP_ATTRIBUTES *attrs)
{
    int rc;
    if(!sftp)
        return LIBSSH2_ERROR_BAD_USE;
    BLOCK_ADJUST(rc, sftp->channel->session,
                 sftp_stat(sftp, path, path_len, stat_type, attrs));
    return rc;
}

/* sftp_symlink
 * Read or set a symlink
 */
static int sftp_symlink(LIBSSH2_SFTP *sftp, const char *path,
                        unsigned int path_len, char *target,
                        unsigned int target_len, int link_type)
{
    LIBSSH2_CHANNEL *channel = sftp->channel;
    LIBSSH2_SESSION *session = channel->session;
    size_t data_len, link_len;
    /* 13 = packet_len(4) + packet_type(1) + request_id(4) + path_len(4) */
    ssize_t packet_len =
        path_len + 13 +
        ((link_type == LIBSSH2_SFTP_SYMLINK) ? (4 + target_len) : 0);
    unsigned char *s, *data;
    static const unsigned char link_responses[2] =
        { SSH_FXP_NAME, SSH_FXP_STATUS };
    int retcode;

    if ((sftp->version < 3) && (link_type != LIBSSH2_SFTP_REALPATH)) {
        return _libssh2_error(session, LIBSSH2_ERROR_SFTP_PROTOCOL,
                              "Server does not support SYMLINK or READLINK");
    }

    if (sftp->symlink_state == libssh2_NB_state_idle) {
        s = sftp->symlink_packet = LIBSSH2_ALLOC(session, packet_len);
        if (!sftp->symlink_packet) {
            return _libssh2_error(session, LIBSSH2_ERROR_ALLOC,
                                  "Unable to allocate memory for "
                                  "SYMLINK/READLINK/REALPATH packet");
        }

        _libssh2_debug(session, LIBSSH2_TRACE_SFTP, "%s %s on %s",
                       (link_type ==
                        LIBSSH2_SFTP_SYMLINK) ? "Creating" : "Reading",
                       (link_type ==
                        LIBSSH2_SFTP_REALPATH) ? "realpath" : "symlink", path);

        _libssh2_store_u32(&s, packet_len - 4);

        switch (link_type) {
        case LIBSSH2_SFTP_REALPATH:
            *(s++) = SSH_FXP_REALPATH;
            break;

        case LIBSSH2_SFTP_SYMLINK:
            *(s++) = SSH_FXP_SYMLINK;
            break;

        case LIBSSH2_SFTP_READLINK:
        default:
            *(s++) = SSH_FXP_READLINK;
        }
        sftp->symlink_request_id = sftp->request_id++;
        _libssh2_store_u32(&s, sftp->symlink_request_id);
        _libssh2_store_str(&s, path, path_len);

        if (link_type == LIBSSH2_SFTP_SYMLINK)
            _libssh2_store_str(&s, target, target_len);

        sftp->symlink_state = libssh2_NB_state_created;
    }

    if (sftp->symlink_state == libssh2_NB_state_created) {
        ssize_t rc = _libssh2_channel_write(channel, 0, sftp->symlink_packet,
                                            packet_len);
        if (rc == LIBSSH2_ERROR_EAGAIN)
            return rc;
        else if (packet_len != rc) {
            LIBSSH2_FREE(session, sftp->symlink_packet);
            sftp->symlink_packet = NULL;
            sftp->symlink_state = libssh2_NB_state_idle;
            return _libssh2_error(session, LIBSSH2_ERROR_SOCKET_SEND,
                                  "Unable to send SYMLINK/READLINK command");
        }
        LIBSSH2_FREE(session, sftp->symlink_packet);
        sftp->symlink_packet = NULL;

        sftp->symlink_state = libssh2_NB_state_sent;
    }

    retcode = sftp_packet_requirev(sftp, 2, link_responses,
                                   sftp->symlink_request_id, &data,
                                   &data_len);
    if (retcode == LIBSSH2_ERROR_EAGAIN)
        return retcode;
    else if (retcode) {
        sftp->symlink_state = libssh2_NB_state_idle;
        return _libssh2_error(session, LIBSSH2_ERROR_SOCKET_TIMEOUT,
                              "Timeout waiting for status message");
    }

    sftp->symlink_state = libssh2_NB_state_idle;

    if (data[0] == SSH_FXP_STATUS) {
        int retcode;

        retcode = _libssh2_ntohu32(data + 5);
        LIBSSH2_FREE(session, data);
        if (retcode == LIBSSH2_FX_OK)
            return LIBSSH2_ERROR_NONE;
        else {
            sftp->last_errno = retcode;
            return _libssh2_error(session, LIBSSH2_ERROR_SFTP_PROTOCOL,
                                  "SFTP Protocol Error");
        }
    }

    if (_libssh2_ntohu32(data + 5) < 1) {
        LIBSSH2_FREE(session, data);
        return _libssh2_error(session, LIBSSH2_ERROR_SFTP_PROTOCOL,
                              "Invalid READLINK/REALPATH response, "
                              "no name entries");
    }

    /* this reads a u32 and stores it into a signed 32bit value */
    link_len = _libssh2_ntohu32(data + 9);
    if (link_len < target_len) {
        memcpy(target, data + 13, link_len);
        target[link_len] = 0;
        retcode = (int)link_len;
    }
    else
        retcode = LIBSSH2_ERROR_BUFFER_TOO_SMALL;
    LIBSSH2_FREE(session, data);

    return retcode;
}

/* libssh2_sftp_symlink_ex
 * Read or set a symlink
 */
LIBSSH2_API int
libssh2_sftp_symlink_ex(LIBSSH2_SFTP *sftp, const char *path,
                        unsigned int path_len, char *target,
                        unsigned int target_len, int link_type)
{
    int rc;
    if(!sftp)
        return LIBSSH2_ERROR_BAD_USE;
    BLOCK_ADJUST(rc, sftp->channel->session,
                 sftp_symlink(sftp, path, path_len, target, target_len,
                              link_type));
    return rc;
}

/* libssh2_sftp_last_error
 * Returns the last error code reported by SFTP
 */
LIBSSH2_API unsigned long
libssh2_sftp_last_error(LIBSSH2_SFTP *sftp)
{
    if(!sftp)
       return 0;

    return sftp->last_errno;
}