diff options
Diffstat (limited to '')
| -rw-r--r-- | sql/field_comp.cc | 154 |
1 files changed, 154 insertions, 0 deletions
diff --git a/sql/field_comp.cc b/sql/field_comp.cc new file mode 100644 index 00000000..ab97c8cc --- /dev/null +++ b/sql/field_comp.cc @@ -0,0 +1,154 @@ +/* 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) + { + int res= deflate(&stream, Z_FINISH); + if (deflateEnd(&stream) == Z_OK && res == Z_STREAM_END) + 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) + { + int res= inflate(&stream, Z_FINISH); + if (inflateEnd(&stream) == Z_OK && res == Z_STREAM_END) + { + 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 } +}; |