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-rw-r--r--sql/field_comp.cc154
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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)
+ {
+ 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 }
+};