src/comp.c

/* Copyright (c) 2004-2005, Sara Golemon <sarag@libssh2.org>
 * 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 "libssh2_priv.h"
#include <zlib.h>

/* ********
   * none *
   ******** */

/* {{{ libssh2_comp_method_none_comp
 * Minimalist compression: Absolutely none
 */
static int libssh2_comp_method_none_comp(LIBSSH2_SESSION *session, int compress,
										 unsigned char **dest, unsigned long *dest_len, unsigned long payload_limit, int *free_dest,
										 const unsigned char *src, unsigned long src_len, void **abstract)
{
	*dest = (unsigned char *)src;
	*dest_len = src_len;

	*free_dest = 0;

	return 0;
}
/* }}} */

static LIBSSH2_COMP_METHOD libssh2_comp_method_none = {
	"none",
	NULL,
	libssh2_comp_method_none_comp,
	NULL
};

#ifdef LIBSSH2_HAVE_ZLIB
/* ********
   * zlib *
   ******** */

/* {{{ Memory management wrappers
 * Yes, I realize we're doing a callback to a callback,
 * Deal...
 */

static voidpf libssh2_comp_method_zlib_alloc(voidpf opaque, uInt items, uInt size)
{
	LIBSSH2_SESSION *session = (LIBSSH2_SESSION*)opaque;

	return (voidpf)LIBSSH2_ALLOC(session, items * size);
}

static void libssh2_comp_method_zlib_free(voidpf opaque, voidpf address)
{
	LIBSSH2_SESSION *session = (LIBSSH2_SESSION*)opaque;

	LIBSSH2_FREE(session, address);
}
/* }}} */

/* {{{ libssh2_comp_method_zlib_init
 * All your bandwidth are belong to us (so save some)
 */
static int libssh2_comp_method_zlib_init(LIBSSH2_SESSION *session, int compress, void **abstract)
{
	z_stream *strm;
	int status;

	strm = LIBSSH2_ALLOC(session, sizeof(z_stream));
	if (!strm) {
		libssh2_error(session, LIBSSH2_ERROR_ALLOC, "Unable to allocate memory for zlib compression/decompression", 0);
		return -1;
	}
	memset(strm, 0, sizeof(z_stream));

	strm->opaque = (voidpf)session;
	strm->zalloc = (alloc_func)libssh2_comp_method_zlib_alloc;
	strm->zfree = (free_func)libssh2_comp_method_zlib_free;
	if (compress) {
		/* deflate */
		status = deflateInit(strm, Z_DEFAULT_COMPRESSION);
	} else {
		/* inflate */
		status = inflateInit(strm);
	}

	if (status != Z_OK) {
		LIBSSH2_FREE(session, strm);
		return -1;
	}
	*abstract = strm;

	return 0;
}
/* }}} */

/* {{{ libssh2_comp_method_zlib_comp
 * zlib, a compression standard for all occasions
 */
static int libssh2_comp_method_zlib_comp(LIBSSH2_SESSION *session, int compress,
										 unsigned char **dest, unsigned long *dest_len, unsigned long payload_limit, int *free_dest,
										 const unsigned char *src, unsigned long src_len, void **abstract)
{
	z_stream *strm = *abstract;
	/* A short-term alloc of a full data chunk is better than a series of reallocs */
	char *out;
	int out_maxlen = compress ? (src_len + 4) : (2 * src_len);
	int limiter = 0;

	/* In practice they never come smaller than this */
	if (out_maxlen < 25) {
		out_maxlen = 25;
	}

	if (out_maxlen > payload_limit) {
		out_maxlen = payload_limit;
	}

	strm->next_in = (char *)src;
	strm->avail_in = src_len;
	out = strm->next_out = LIBSSH2_ALLOC(session, out_maxlen);
	strm->avail_out = out_maxlen;
	if (!strm->next_out) {
		libssh2_error(session, LIBSSH2_ERROR_ALLOC, "Unable to allocate compression/decompression buffer", 0);
		return -1;
	}
	while (strm->avail_in) {
		int status;

		if (compress) {
			status = deflate(strm, Z_PARTIAL_FLUSH);
		} else {
			status = inflate(strm, Z_PARTIAL_FLUSH);
		}
		if (status != Z_OK) {
			libssh2_error(session, LIBSSH2_ERROR_ZLIB, "compress/decompression failure", 0);
			LIBSSH2_FREE(session, out);
			return -1;
		}
		if (strm->avail_in) {
			unsigned long out_ofs = out_maxlen - strm->avail_out;

			out_maxlen += compress ? (strm->avail_in + 4) : (2 * strm->avail_in);

			if ((out_maxlen > payload_limit) && !compress && limiter++) {
				libssh2_error(session, LIBSSH2_ERROR_ZLIB, "Excessive growth in decompression phase", 0);
				LIBSSH2_FREE(session, out);
				return -1;
			}

			out = LIBSSH2_REALLOC(session, out, out_maxlen);	
			if (!out) {
				libssh2_error(session, LIBSSH2_ERROR_ALLOC, "Unable to expand compress/decompression buffer", 0);
				return -1;
			}
			strm->next_out = out + out_ofs;
			strm->avail_out += compress ? (strm->avail_in + 4) : (2 * strm->avail_in);
		} else while (!strm->avail_out) {
			/* Done with input, might be a byte or two in internal buffer during compress
			 * Or potentially many bytes if it's a decompress
			 */
			int grow_size = compress ? 8 : 1024;

			if (out_maxlen >= payload_limit) {
				libssh2_error(session, LIBSSH2_ERROR_ZLIB, "Excessive growth in decompression phase", 0);
				LIBSSH2_FREE(session, out);
				return -1;
			}

			if (grow_size > (payload_limit - out_maxlen)) {
				grow_size = payload_limit - out_maxlen;
			}

			out_maxlen += grow_size;
			strm->avail_out = grow_size;

			out = LIBSSH2_REALLOC(session, out, out_maxlen);
			if (!out) {
				libssh2_error(session, LIBSSH2_ERROR_ALLOC, "Unable to expand final compress/decompress buffer", 0);
				return -1;
			}
			strm->next_out = out + out_maxlen - grow_size;

			if (compress) {
				status = deflate(strm, Z_PARTIAL_FLUSH);
			} else {
				status = inflate(strm, Z_PARTIAL_FLUSH);
			}
			if (status != Z_OK) {
				libssh2_error(session, LIBSSH2_ERROR_ZLIB, "compress/decompression failure", 0);
				LIBSSH2_FREE(session, out);
				return -1;
			}
		}
	}

	*dest = out;
	*dest_len = out_maxlen - strm->avail_out;
	*free_dest = 1;

	return 0;
}
/* }}} */

/* {{{ libssh2_comp_method_zlib_dtor
 * All done, no more compression for you
 */
static int libssh2_comp_method_zlib_dtor(LIBSSH2_SESSION *session, int compress, void **abstract)
{
	z_stream *strm = *abstract;

	if (strm) {
		if (compress) {
			/* deflate */
			deflateEnd(strm);
		} else {
			/* inflate */
			inflateEnd(strm);
		}

		LIBSSH2_FREE(session, strm);
	}

	*abstract = NULL;

	return 0;
}
/* }}} */

static LIBSSH2_COMP_METHOD libssh2_comp_method_zlib = {
	"zlib",
	libssh2_comp_method_zlib_init,
	libssh2_comp_method_zlib_comp,
	libssh2_comp_method_zlib_dtor,
};
#endif /* LIBSSH2_HAVE_ZLIB */

/* ***********************
   * Compression Methods *
   *********************** */

static LIBSSH2_COMP_METHOD *_libssh2_comp_methods[] = {
	&libssh2_comp_method_none,
#ifdef LIBSSH2_HAVE_ZLIB
	&libssh2_comp_method_zlib,
#endif /* LIBSSH2_HAVE_ZLIB */
	NULL
};

LIBSSH2_COMP_METHOD **libssh2_comp_methods(void) {
	return _libssh2_comp_methods;
}