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/* Copyright (C) 2017 MariaDB Foundation
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
#include <my_global.h>
#include "sql_string.h"
#include "sql_class.h"
#include "field_comp.h"
#include <zlib.h>
/**
Compresses string using zlib
@param[out] to destination buffer for compressed data
@param[in] from data to compress
@param[in] length from length
Requirement is such that string stored at `to' must not exceed `from' length.
Otherwise 0 is returned and caller stores string uncompressed.
`to' must be large enough to hold `length' bytes.
length == 1 is an edge case that may break stream.avail_out calculation: at
least 2 bytes required to store metadata.
*/
static uint compress_zlib(THD *thd, char *to, const char *from, uint length)
{
uint level= thd->variables.column_compression_zlib_level;
/* Caller takes care of empty strings. */
DBUG_ASSERT(length);
if (level > 0 && length > 1)
{
z_stream stream;
int wbits= thd->variables.column_compression_zlib_wrap ? MAX_WBITS :
-MAX_WBITS;
uint strategy= thd->variables.column_compression_zlib_strategy;
/* Store only meaningful bytes of original data length. */
uchar original_pack_length= number_storage_requirement(length);
*to= 0x80 + original_pack_length + (wbits < 0 ? 8 : 0);
store_bigendian(length, (uchar*) to + 1, original_pack_length);
stream.avail_in= length;
stream.next_in= (Bytef*) from;
DBUG_ASSERT(length >= static_cast<uint>(original_pack_length) + 1);
stream.avail_out= length - original_pack_length - 1;
stream.next_out= (Bytef*) to + original_pack_length + 1;
stream.zalloc= 0;
stream.zfree= 0;
stream.opaque= 0;
if (deflateInit2(&stream, level, Z_DEFLATED, wbits, 8, strategy) == Z_OK &&
deflate(&stream, Z_FINISH) == Z_STREAM_END &&
deflateEnd(&stream) == Z_OK)
return (uint) (stream.next_out - (Bytef*) to);
}
return 0;
}
static int uncompress_zlib(String *to, const uchar *from, uint from_length,
uint field_length)
{
z_stream stream;
uchar original_pack_length;
int wbits;
ulonglong avail_out;
original_pack_length= *from & 0x07;
wbits= *from & 8 ? -MAX_WBITS : MAX_WBITS;
from++;
from_length--;
if (from_length < original_pack_length)
{
my_error(ER_ZLIB_Z_DATA_ERROR, MYF(0));
return 1;
}
avail_out= (ulonglong)read_bigendian(from, original_pack_length);
if (avail_out > field_length)
{
my_error(ER_ZLIB_Z_DATA_ERROR, MYF(0));
return 1;
}
stream.avail_out= (uint)avail_out;
if (to->alloc(stream.avail_out))
return 1;
stream.next_out= (Bytef*) to->ptr();
stream.avail_in= from_length - original_pack_length;
stream.next_in= (Bytef*) from + original_pack_length;
stream.zalloc= 0;
stream.zfree= 0;
stream.opaque= 0;
if (inflateInit2(&stream, wbits) == Z_OK &&
inflate(&stream, Z_FINISH) == Z_STREAM_END &&
inflateEnd(&stream) == Z_OK)
{
to->length(stream.total_out);
return 0;
}
my_error(ER_ZLIB_Z_DATA_ERROR, MYF(0));
return 1;
}
Compression_method compression_methods[MAX_COMPRESSION_METHODS]=
{
{ 0, 0, 0 },
{ 0, 0, 0 },
{ 0, 0, 0 },
{ 0, 0, 0 },
{ 0, 0, 0 },
{ 0, 0, 0 },
{ 0, 0, 0 },
{ 0, 0, 0 },
{ "zlib", compress_zlib, uncompress_zlib },
{ 0, 0, 0 },
{ 0, 0, 0 },
{ 0, 0, 0 },
{ 0, 0, 0 },
{ 0, 0, 0 },
{ 0, 0, 0 },
{ 0, 0, 0 }
};
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