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/*-
* Public Domain 2014-2015 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 <lz4.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <wiredtiger.h>
#include <wiredtiger_ext.h>
/*
* We need to include the configuration file to detect whether this extension
* is being built into the WiredTiger library.
*/
#include "wiredtiger_config.h"
/* Local compressor structure. */
typedef struct {
WT_COMPRESSOR compressor; /* Must come first */
WT_EXTENSION_API *wt_api; /* Extension API */
} LZ4_COMPRESSOR;
/*
* wt_lz4_error --
* Output an error message, and return a standard error code.
*/
static int
wt_lz4_error(
WT_COMPRESSOR *compressor, WT_SESSION *session, const char *call, int zret)
{
WT_EXTENSION_API *wt_api;
wt_api = ((LZ4_COMPRESSOR *)compressor)->wt_api;
(void)wt_api->err_printf(wt_api,
session, "lz4 error: %s: %d", call, zret);
return (WT_ERROR);
}
/*
* wt_lz4_compress --
* WiredTiger LZ4 compression.
*/
static int
wt_lz4_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)
{
char *lz4buf;
size_t lz4_len;
/*
* The buffer should always be large enough due to the lz4_pre_size
* call, but be paranoid and error if it isn't.
*/
if (dst_len < src_len + sizeof(size_t))
return (wt_lz4_error(compressor, session,
"LZ4 compress buffer too small", 0));
/* Store the length of the compressed block in the first 8 bytes. */
lz4buf = (char *)dst + sizeof(size_t);
lz4_len = (size_t)LZ4_compress((const char *)src, lz4buf, (int)src_len);
/*
* Flag no-compression if the result was larger than the original
* size or compression failed.
*/
if (lz4_len == 0 || lz4_len + sizeof(size_t) >= src_len)
*compression_failed = 1;
else {
/*
* On decompression, lz4 requires the exact compressed byte
* count (the current value of lz4_len). WiredTiger does not
* preserve that value, so save lz4_len at the beginning of the
* destination buffer.
*/
*(size_t *)dst = lz4_len;
*result_lenp = lz4_len + sizeof(size_t);
*compression_failed = 0;
}
return (0);
}
/*
* wt_lz4_decompress --
* WiredTiger LZ4 decompression.
*/
static int
wt_lz4_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;
char *compressed_data;
int decoded;
size_t src_data_len;
wt_api = ((LZ4_COMPRESSOR *)compressor)->wt_api;
/* Retrieve compressed length from start of the data buffer. */
src_data_len = *(size_t *)src;
if (src_data_len + sizeof(size_t) > src_len) {
(void)wt_api->err_printf(wt_api,
session,
"wt_lz4_decompress: stored size exceeds buffer size");
return (WT_ERROR);
}
/* Skip over the data size to the start of compressed data. */
compressed_data = (char *)src + sizeof(size_t);
/*
* The destination buffer length should always be sufficient because
* wiredtiger keeps track of the byte count before compression. Use
* safe decompression: we may be relying on decompression to detect
* corruption.
*/
decoded = LZ4_decompress_safe(
compressed_data, (char *)dst, (int)src_data_len, (int)dst_len);
if (decoded < 0)
return (wt_lz4_error(compressor, session,
"LZ4 decompress error", decoded));
/* return the uncompressed data length */
*result_lenp = dst_len;
return (0);
}
/*
* wt_lz4_pre_size --
* WiredTiger LZ4 destination buffer sizing for compression.
*/
static int
wt_lz4_pre_size(WT_COMPRESSOR *compressor, WT_SESSION *session,
uint8_t *src, size_t src_len,
size_t *result_lenp)
{
(void)compressor;
(void)session;
(void)src;
/*
* LZ4 can use more space than the input data size, use the library
* calculation of that overhead (plus our overhead) to be safe.
*/
*result_lenp = LZ4_COMPRESSBOUND(src_len) + sizeof(size_t);
return (0);
}
/*
* wt_lz4_terminate --
* WiredTiger LZ4 compression termination.
*/
static int
wt_lz4_terminate(WT_COMPRESSOR *compressor, WT_SESSION *session)
{
(void)session;
/* Free the allocated memory. */
free(compressor);
return (0);
}
int lz4_extension_init(WT_CONNECTION *, WT_CONFIG_ARG *);
/*
* lz4_extension_init --
* A simple shared library compression example.
*/
int
lz4_extension_init(WT_CONNECTION *connection, WT_CONFIG_ARG *config)
{
LZ4_COMPRESSOR *lz4_compressor;
(void)config; /* Unused parameters */
if ((lz4_compressor = calloc(1, sizeof(LZ4_COMPRESSOR))) == NULL)
return (errno);
/*
* Allocate a local compressor structure, with a WT_COMPRESSOR structure
* as the first field, allowing us to treat references to either type of
* structure as a reference to the other type.
*
* This could be simplified if only a single database is opened in the
* application, we could use a static WT_COMPRESSOR structure, and a
* static reference to the WT_EXTENSION_API methods, then we don't need
* to allocate memory when the compressor is initialized or free it when
* the compressor is terminated. However, this approach is more general
* purpose and supports multiple databases per application.
*/
lz4_compressor->compressor.compress = wt_lz4_compress;
lz4_compressor->compressor.compress_raw = NULL;
lz4_compressor->compressor.decompress = wt_lz4_decompress;
lz4_compressor->compressor.pre_size = wt_lz4_pre_size;
lz4_compressor->compressor.terminate = wt_lz4_terminate;
lz4_compressor->wt_api = connection->get_extension_api(connection);
/* Load the compressor */
return (connection->add_compressor(
connection, "lz4", (WT_COMPRESSOR *)lz4_compressor, NULL));
}
/*
* We have to remove this symbol when building as a builtin extension otherwise
* it will conflict with other builtin libraries.
*/
#ifndef HAVE_BUILTIN_EXTENSION_LZ4
/*
* wiredtiger_extension_init --
* WiredTiger LZ4 compression extension.
*/
int
wiredtiger_extension_init(WT_CONNECTION *connection, WT_CONFIG_ARG *config)
{
return lz4_extension_init(connection, config);
}
#endif
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