path: root/src/third_party/wiredtiger/ext/compressors/zstd/zstd_compress.c

/*-
 * Public Domain 2014-2020 MongoDB, Inc.
 * Public Domain 2008-2014 WiredTiger, Inc.
 *
 * This is free and unencumbered software released into the public domain.
 *
 * Anyone is free to copy, modify, publish, use, compile, sell, or
 * distribute this software, either in source code form or as a compiled
 * binary, for any purpose, commercial or non-commercial, and by any
 * means.
 *
 * In jurisdictions that recognize copyright laws, the author or authors
 * of this software dedicate any and all copyright interest in the
 * software to the public domain. We make this dedication for the benefit
 * of the public at large and to the detriment of our heirs and
 * successors. We intend this dedication to be an overt act of
 * relinquishment in perpetuity of all present and future rights to this
 * software under copyright law.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 */

#include <zstd.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>

/*
 * We need to include the configuration file to detect whether this extension is being built into
 * the WiredTiger library; application-loaded compression functions won't need it.
 */
#include <wiredtiger_config.h>

#include <wiredtiger.h>
#include <wiredtiger_ext.h>

#ifdef _MSC_VER
#define inline __inline
#endif

/* Local compressor structure. */
typedef struct {
    WT_COMPRESSOR compressor; /* Must come first */

    WT_EXTENSION_API *wt_api; /* Extension API */

    int compression_level; /* compression level */
} ZSTD_COMPRESSOR;

/*
 * Zstd decompression requires an exact compressed byte count. WiredTiger doesn't track that value,
 * store it in the destination buffer.
 */
#define ZSTD_PREFIX sizeof(uint64_t)

#ifdef WORDS_BIGENDIAN
/*
 * zstd_bswap64 --
 *     64-bit unsigned little-endian to/from big-endian value.
 */
static inline uint64_t
zstd_bswap64(uint64_t v)
{
    return (((v << 56) & 0xff00000000000000UL) | ((v << 40) & 0x00ff000000000000UL) |
      ((v << 24) & 0x0000ff0000000000UL) | ((v << 8) & 0x000000ff00000000UL) |
      ((v >> 8) & 0x00000000ff000000UL) | ((v >> 24) & 0x0000000000ff0000UL) |
      ((v >> 40) & 0x000000000000ff00UL) | ((v >> 56) & 0x00000000000000ffUL));
}
#endif

/*
 * zstd_error --
 *     Output an error message, and return a standard error code.
 */
static int
zstd_error(WT_COMPRESSOR *compressor, WT_SESSION *session, const char *call, size_t error)
{
    WT_EXTENSION_API *wt_api;

    wt_api = ((ZSTD_COMPRESSOR *)compressor)->wt_api;

    (void)wt_api->err_printf(wt_api, session, "zstd error: %s: %s", call, ZSTD_getErrorName(error));
    return (WT_ERROR);
}

/*
 *  zstd_compress --
 *	WiredTiger Zstd compression.
 */
static int
zstd_compress(WT_COMPRESSOR *compressor, WT_SESSION *session, uint8_t *src, size_t src_len,
  uint8_t *dst, size_t dst_len, size_t *result_lenp, int *compression_failed)
{
    ZSTD_COMPRESSOR *zcompressor;
    size_t zstd_ret;
    uint64_t zstd_len;

    zcompressor = (ZSTD_COMPRESSOR *)compressor;

    /* Compress, starting past the prefix bytes. */
    zstd_ret = ZSTD_compress(
      dst + ZSTD_PREFIX, dst_len - ZSTD_PREFIX, src, src_len, zcompressor->compression_level);

    /*
     * If compression succeeded and the compressed length is smaller than the original size, return
     * success.
     */
    if (!ZSTD_isError(zstd_ret) && zstd_ret + ZSTD_PREFIX < src_len) {
        *result_lenp = zstd_ret + ZSTD_PREFIX;
        *compression_failed = 0;

        /*
         * On decompression, Zstd requires an exact compressed byte count (the current value of
         * zstd_ret). WiredTiger does not preserve that value, so save zstd_ret at the beginning of
         * the destination buffer.
         *
         * Store the value in little-endian format.
         */
        zstd_len = zstd_ret;
#ifdef WORDS_BIGENDIAN
        zstd_len = zstd_bswap64(zstd_len);
#endif
        *(uint64_t *)dst = zstd_len;
        return (0);
    }

    *compression_failed = 1;
    return (
      ZSTD_isError(zstd_ret) ? zstd_error(compressor, session, "ZSTD_compress", zstd_ret) : 0);
}

/*
 * zstd_decompress --
 *     WiredTiger Zstd decompression.
 */
static int
zstd_decompress(WT_COMPRESSOR *compressor, WT_SESSION *session, uint8_t *src, size_t src_len,
  uint8_t *dst, size_t dst_len, size_t *result_lenp)
{
    WT_EXTENSION_API *wt_api;
    size_t zstd_ret;
    uint64_t zstd_len;

    wt_api = ((ZSTD_COMPRESSOR *)compressor)->wt_api;

    /*
     * Retrieve the saved length, handling little- to big-endian conversion as necessary.
     */
    zstd_len = *(uint64_t *)src;
#ifdef WORDS_BIGENDIAN
    zstd_len = zstd_bswap64(zstd_len);
#endif
    if (zstd_len + ZSTD_PREFIX > src_len) {
        (void)wt_api->err_printf(wt_api, session,
          "WT_COMPRESSOR.decompress: stored size exceeds source "
          "size");
        return (WT_ERROR);
    }

    zstd_ret = ZSTD_decompress(dst, dst_len, src + ZSTD_PREFIX, (size_t)zstd_len);

    if (!ZSTD_isError(zstd_ret)) {
        *result_lenp = zstd_ret;
        return (0);
    }
    return (zstd_error(compressor, session, "ZSTD_decompress", zstd_ret));
}

/*
 * zstd_pre_size --
 *     WiredTiger Zstd destination buffer sizing for compression.
 */
static int
zstd_pre_size(
  WT_COMPRESSOR *compressor, WT_SESSION *session, uint8_t *src, size_t src_len, size_t *result_lenp)
{
    (void)compressor; /* Unused parameters */
    (void)session;
    (void)src;

    /*
     * Zstd compression runs faster if the destination buffer is sized at the upper-bound of the
     * buffer size needed by the compression. Use the library calculation of that overhead (plus our
     * overhead).
     */
    *result_lenp = ZSTD_compressBound(src_len) + ZSTD_PREFIX;
    return (0);
}

/*
 * zstd_terminate --
 *     WiredTiger Zstd compression termination.
 */
static int
zstd_terminate(WT_COMPRESSOR *compressor, WT_SESSION *session)
{
    (void)session; /* Unused parameters */

    free(compressor);
    return (0);
}

/*
 * zstd_init_config --
 *     Handle zstd configuration.
 */
static int
zstd_init_config(WT_CONNECTION *connection, WT_CONFIG_ARG *config, int *compression_levelp)
{
    WT_CONFIG_ITEM v;
    WT_EXTENSION_API *wt_api;
    int ret;

    /* If configured as a built-in, there's no configuration argument. */
    if (config == NULL)
        return (0);

    /*
     * Zstd compression engine allows applications to specify a compression level; review the
     * configuration.
     */
    wt_api = connection->get_extension_api(connection);
    if ((ret = wt_api->config_get(wt_api, NULL, config, "compression_level", &v)) == 0)
        *compression_levelp = (int)v.val;
    else if (ret != WT_NOTFOUND) {
        (void)wt_api->err_printf(
          wt_api, NULL, "zstd_init_config: %s", wt_api->strerror(wt_api, NULL, ret));
        return (ret);
    }

    return (0);
}

int zstd_extension_init(WT_CONNECTION *, WT_CONFIG_ARG *);

/*
 * zstd_extension_init --
 *     WiredTiger Zstd compression extension - called directly when Zstd support is built in, or via
 *     wiredtiger_extension_init when Zstd support is included via extension loading.
 */
int
zstd_extension_init(WT_CONNECTION *connection, WT_CONFIG_ARG *config)
{
    ZSTD_COMPRESSOR *zstd_compressor;
    int compression_level, ret;

    /*
     * Zstd's sweet-spot is better compression than zlib at significantly
     * faster compression/decompression speeds. LZ4 and snappy are faster
     * than zstd, but have worse compression ratios. Applications wanting
     * faster compression/decompression with worse compression will select
     * LZ4 or snappy, so we configure zstd for better compression.
     *
     * From the zstd github site, default measurements of the compression
     * engines we support, listing compression ratios with compression and
     * decompression speeds:
     *
     *	Name	Ratio	C.speed	D.speed
     *			MB/s	MB/s
     *	zstd	2.877	330	940
     *	zlib	2.730	95	360
     *	LZ4	2.101	620	3100
     *	snappy	2.091	480	1600
     *
     * Set the zstd compression level to 3: according to the zstd web site,
     * that reduces zstd's compression speed to around 200 MB/s, increasing
     * the compression ratio to 3.100 (close to zlib's best compression
     * ratio). In other words, position zstd as a zlib replacement, having
     * similar compression at much higher compression/decompression speeds.
     */
    compression_level = 6;
    if ((ret = zstd_init_config(connection, config, &compression_level)) != 0)
        return (ret);

    if ((zstd_compressor = calloc(1, sizeof(ZSTD_COMPRESSOR))) == NULL)
        return (errno);

    zstd_compressor->compressor.compress = zstd_compress;
    zstd_compressor->compressor.decompress = zstd_decompress;
    zstd_compressor->compressor.pre_size = zstd_pre_size;
    zstd_compressor->compressor.terminate = zstd_terminate;

    zstd_compressor->wt_api = connection->get_extension_api(connection);

    zstd_compressor->compression_level = compression_level;

    /* Load the compressor */
    if ((ret = connection->add_compressor(
           connection, "zstd", (WT_COMPRESSOR *)zstd_compressor, NULL)) == 0)
        return (0);

    free(zstd_compressor);
    return (ret);
}

/*
 * We have to remove this symbol when building as a builtin extension otherwise it will conflict
 * with other builtin libraries.
 */
#ifndef HAVE_BUILTIN_EXTENSION_ZSTD
/*
 * wiredtiger_extension_init --
 *     WiredTiger Zstd compression extension.
 */
int
wiredtiger_extension_init(WT_CONNECTION *connection, WT_CONFIG_ARG *config)
{
    return (zstd_extension_init(connection, config));
}
#endif