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/*-
* Public Domain 2008-2013 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 <snappy-c.h>
#include <stdlib.h>
#include <string.h>
#include <wiredtiger.h>
#include <wiredtiger_ext.h>
WT_EXTENSION_API *wt_api;
static int
wt_snappy_compress(WT_COMPRESSOR *, WT_SESSION *,
uint8_t *, size_t, uint8_t *, size_t, size_t *, int *);
static int
wt_snappy_decompress(WT_COMPRESSOR *, WT_SESSION *,
uint8_t *, size_t, uint8_t *, size_t, size_t *);
static int
wt_snappy_pre_size(WT_COMPRESSOR *, WT_SESSION *, uint8_t *, size_t, size_t *);
static WT_COMPRESSOR wt_snappy_compressor = {
wt_snappy_compress, NULL, wt_snappy_decompress, wt_snappy_pre_size };
#define __UNUSED(v) ((void)(v))
int
wiredtiger_extension_init(
WT_SESSION *session, WT_EXTENSION_API *api, const char *config)
{
WT_CONNECTION *conn;
__UNUSED(config);
wt_api = api;
conn = session->connection;
return (
conn->add_compressor(conn, "snappy", &wt_snappy_compressor, NULL));
}
/* Snappy WT_COMPRESSOR for WT_CONNECTION::add_compressor. */
/*
* wt_snappy_error --
* Output an error message, and return a standard error code.
*/
static int
wt_snappy_error(WT_SESSION *session, const char *call, snappy_status snret)
{
const char *msg;
switch (snret) {
case SNAPPY_BUFFER_TOO_SMALL:
msg = "SNAPPY_BUFFER_TOO_SMALL";
break;
case SNAPPY_INVALID_INPUT:
msg = "SNAPPY_INVALID_INPUT";
break;
default:
msg = "unknown error";
break;
}
(void)wiredtiger_err_printf(
session, "snappy error: %s: %s: %d", call, msg, snret);
return (WT_ERROR);
}
static int
wt_snappy_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)
{
snappy_status snret;
size_t snaplen;
char *snapbuf;
__UNUSED(compressor);
/*
* dst_len was computed in wt_snappy_pre_size, so we know it's big
* enough. Skip past the space we'll use to store the final count
* of compressed bytes.
*/
snaplen = dst_len - sizeof(size_t);
snapbuf = (char *)dst + sizeof(size_t);
/* snaplen is an input and an output arg. */
snret = snappy_compress((char *)src, src_len, snapbuf, &snaplen);
if (snret == SNAPPY_OK) {
/*
* On decompression, snappy requires the exact compressed byte
* count (the current value of snaplen). WiredTiger does not
* preserve that value, so save snaplen at the beginning of the
* destination buffer.
*/
if (snaplen + sizeof(size_t) < src_len) {
*(size_t *)dst = snaplen;
*result_lenp = snaplen + sizeof(size_t);
*compression_failed = 0;
} else
/* The compressor failed to produce a smaller result. */
*compression_failed = 1;
return (0);
}
return (wt_snappy_error(session, "snappy_compress", snret));
}
static int
wt_snappy_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)
{
snappy_status snret;
size_t snaplen;
__UNUSED(compressor);
/* retrieve the saved length */
snaplen = *(size_t *)src;
if (snaplen + sizeof(size_t) > src_len) {
(void)wiredtiger_err_printf(
session,
"wt_snappy_decompress: stored size exceeds buffer size");
return (WT_ERROR);
}
/* dst_len is an input and an output arg. */
snret = snappy_uncompress(
(char *)src + sizeof(size_t), snaplen, (char *)dst, &dst_len);
if (snret == SNAPPY_OK) {
*result_lenp = dst_len;
return (0);
}
return (wt_snappy_error(session, "snappy_decompress", snret));
}
static int
wt_snappy_pre_size(WT_COMPRESSOR *compressor, WT_SESSION *session,
uint8_t *src, size_t src_len,
size_t *result_lenp)
{
__UNUSED(compressor);
__UNUSED(session);
__UNUSED(src);
/*
* Snappy requires the dest buffer be somewhat larger than the source.
* Fortunately, this is fast to compute, and will give us a dest buffer
* in wt_snappy_compress that we can compress to directly. We add space
* in the dest buffer to store the accurate compressed size.
*/
*result_lenp = snappy_max_compressed_length(src_len) + sizeof(size_t);
return (0);
}
/* End Snappy WT_COMPRESSOR for WT_CONNECTION::add_compressor. */
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