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/*-
* Public Domain 2014-2018 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
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