libstats/socket/stats_event_list.c

/*
 * Copyright (C) 2018, The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "include/stats_event_list.h"

#include <string.h>
#include <sys/time.h>
#include "stats_buffer_writer.h"

#define MAX_EVENT_PAYLOAD (LOGGER_ENTRY_MAX_PAYLOAD - sizeof(int32_t))

typedef struct {
    uint32_t tag;
    unsigned pos;                                    /* Read/write position into buffer */
    unsigned count[ANDROID_MAX_LIST_NEST_DEPTH + 1]; /* Number of elements   */
    unsigned list[ANDROID_MAX_LIST_NEST_DEPTH + 1];  /* pos for list counter */
    unsigned list_nest_depth;
    unsigned len; /* Length or raw buffer. */
    bool overflow;
    bool list_stop; /* next call decrement list_nest_depth and issue a stop */
    enum {
        kAndroidLoggerRead = 1,
        kAndroidLoggerWrite = 2,
    } read_write_flag;
    uint8_t storage[LOGGER_ENTRY_MAX_PAYLOAD];
} android_log_context_internal;

// Similar to create_android_logger(), but instead of allocation a new buffer,
// this function resets the buffer for resuse.
void reset_log_context(android_log_context ctx) {
    if (!ctx) {
        return;
    }
    android_log_context_internal* context = (android_log_context_internal*)(ctx);
    uint32_t tag = context->tag;
    memset(context, 0, sizeof(android_log_context_internal));

    context->tag = tag;
    context->read_write_flag = kAndroidLoggerWrite;
    size_t needed = sizeof(uint8_t) + sizeof(uint8_t);
    if ((context->pos + needed) > MAX_EVENT_PAYLOAD) {
        context->overflow = true;
    }
    /* Everything is a list */
    context->storage[context->pos + 0] = EVENT_TYPE_LIST;
    context->list[0] = context->pos + 1;
    context->pos += needed;
}

int stats_write_list(android_log_context ctx) {
    android_log_context_internal* context;
    const char* msg;
    ssize_t len;

    context = (android_log_context_internal*)(ctx);
    if (!context || (kAndroidLoggerWrite != context->read_write_flag)) {
        return -EBADF;
    }

    if (context->list_nest_depth) {
        return -EIO;
    }

    /* NB: if there was overflow, then log is truncated. Nothing reported */
    context->storage[1] = context->count[0];
    len = context->len = context->pos;
    msg = (const char*)context->storage;
    /* it's not a list */
    if (context->count[0] <= 1) {
        len -= sizeof(uint8_t) + sizeof(uint8_t);
        if (len < 0) {
            len = 0;
        }
        msg += sizeof(uint8_t) + sizeof(uint8_t);
    }

    return write_buffer_to_statsd((void*)msg, len, 0);
}

int write_to_logger(android_log_context ctx, log_id_t id) {
    int retValue = 0;

    if (WRITE_TO_LOGD) {
        retValue = android_log_write_list(ctx, id);
    }

    if (WRITE_TO_STATSD) {
        // log_event_list's cast operator is overloaded.
        int ret = stats_write_list(ctx);
        // In debugging phase, we may write to both logd and statsd. Prefer to
        // return statsd socket write error code here.
        if (ret < 0) {
            retValue = ret;
        }
    }

    return retValue;
}

static inline void copy4LE(uint8_t* buf, uint32_t val) {
    buf[0] = val & 0xFF;
    buf[1] = (val >> 8) & 0xFF;
    buf[2] = (val >> 16) & 0xFF;
    buf[3] = (val >> 24) & 0xFF;
}

// Note: this function differs from android_log_write_string8_len in that the length passed in
// should be treated as actual length and not max length.
int android_log_write_char_array(android_log_context ctx, const char* value, size_t actual_len) {
    size_t needed;
    ssize_t len = actual_len;
    android_log_context_internal* context;

    context = (android_log_context_internal*)ctx;
    if (!context || (kAndroidLoggerWrite != context->read_write_flag)) {
        return -EBADF;
    }
    if (context->overflow) {
        return -EIO;
    }
    if (!value) {
        value = "";
        len = 0;
    }
    needed = sizeof(uint8_t) + sizeof(int32_t) + len;
    if ((context->pos + needed) > MAX_EVENT_PAYLOAD) {
        /* Truncate string for delivery */
        len = MAX_EVENT_PAYLOAD - context->pos - 1 - sizeof(int32_t);
        if (len <= 0) {
            context->overflow = true;
            return -EIO;
        }
    }
    context->count[context->list_nest_depth]++;
    context->storage[context->pos + 0] = EVENT_TYPE_STRING;
    copy4LE(&context->storage[context->pos + 1], len);
    if (len) {
        memcpy(&context->storage[context->pos + 5], value, len);
    }
    context->pos += needed;
    return len;
}