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/**
* @file
* ZLIB compression
*
* @authors
* Copyright (C) 2019-2020 Tino Reichardt <milky-neomutt@mcmilk.de>
* Copyright (C) 2020 Pietro Cerutti <gahr@gahr.ch>
* Copyright (C) 2020-2023 Richard Russon <rich@flatcap.org>
*
* @copyright
* 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, either version 2 of the License, or (at your option) any later
* version.
*
* 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, see <http://www.gnu.org/licenses/>.
*/
/**
* @page compress_zlib ZLIB compression
*
* ZLIB compression.
* https://www.zlib.net/
*/
#include "config.h"
#include <stddef.h>
#include <zconf.h>
#include <zlib.h>
#include "private.h"
#include "mutt/lib.h"
#include "lib.h"
#define MIN_COMP_LEVEL 1 ///< Minimum compression level for zlib
#define MAX_COMP_LEVEL 9 ///< Maximum compression level for zlib
/**
* struct ZlibComprData - Private Zlib Compression Data
*/
struct ZlibComprData
{
void *buf; ///< Temporary buffer
short level; ///< Compression Level to be used
};
/**
* zlib_cdata_free - Free Zlib Compression Data
* @param ptr Zlib Compression Data to free
*/
void zlib_cdata_free(struct ZlibComprData **ptr)
{
if (!ptr || !*ptr)
return;
struct ZlibComprData *cdata = *ptr;
FREE(&cdata->buf);
FREE(ptr);
}
/**
* zlib_cdata_new - Create new Zlib Compression Data
* @retval ptr New Zlib Compression Data
*/
static struct ZlibComprData *zlib_cdata_new(void)
{
return MUTT_MEM_CALLOC(1, struct ZlibComprData);
}
/**
* compr_zlib_open - Open a compression context - Implements ComprOps::open() - @ingroup compress_open
*/
static ComprHandle *compr_zlib_open(short level)
{
struct ZlibComprData *cdata = zlib_cdata_new();
cdata->buf = mutt_mem_calloc(compressBound(1024 * 32), 1);
if ((level < MIN_COMP_LEVEL) || (level > MAX_COMP_LEVEL))
{
mutt_debug(LL_DEBUG1, "The compression level for %s should be between %d and %d\n",
compr_zlib_ops.name, MIN_COMP_LEVEL, MAX_COMP_LEVEL);
level = MIN_COMP_LEVEL;
}
cdata->level = level;
// Return an opaque pointer
return (ComprHandle *) cdata;
}
/**
* compr_zlib_compress - Compress header cache data - Implements ComprOps::compress() - @ingroup compress_compress
*/
static void *compr_zlib_compress(ComprHandle *handle, const char *data,
size_t dlen, size_t *clen)
{
if (!handle)
return NULL;
// Decloak an opaque pointer
struct ZlibComprData *cdata = handle;
uLong len = compressBound(dlen);
mutt_mem_realloc(&cdata->buf, len + 4);
Bytef *cbuf = (unsigned char *) cdata->buf + 4;
const void *ubuf = data;
int rc = compress2(cbuf, &len, ubuf, dlen, cdata->level);
if (rc != Z_OK)
return NULL; // LCOV_EXCL_LINE
*clen = len + 4;
/* save ulen to first 4 bytes */
unsigned char *cs = cdata->buf;
cs[0] = dlen & 0xff;
dlen >>= 8;
cs[1] = dlen & 0xff;
dlen >>= 8;
cs[2] = dlen & 0xff;
dlen >>= 8;
cs[3] = dlen & 0xff;
return cdata->buf;
}
/**
* compr_zlib_decompress - Decompress header cache data - Implements ComprOps::decompress() - @ingroup compress_decompress
*/
static void *compr_zlib_decompress(ComprHandle *handle, const char *cbuf, size_t clen)
{
if (!handle)
return NULL;
// Decloak an opaque pointer
struct ZlibComprData *cdata = handle;
/* first 4 bytes store the size */
const unsigned char *cs = (const unsigned char *) cbuf;
if (clen < 4)
return NULL;
uLong ulen = cs[0] + (cs[1] << 8) + (cs[2] << 16) + ((uLong) cs[3] << 24);
if (ulen == 0)
return NULL;
mutt_mem_realloc(&cdata->buf, ulen);
Bytef *ubuf = cdata->buf;
cs = (const unsigned char *) cbuf;
int rc = uncompress(ubuf, &ulen, cs + 4, clen - 4);
if (rc != Z_OK)
return NULL;
return ubuf;
}
/**
* compr_zlib_close - Close a compression context - Implements ComprOps::close() - @ingroup compress_close
*/
static void compr_zlib_close(ComprHandle **ptr)
{
if (!ptr || !*ptr)
return;
// Decloak an opaque pointer
zlib_cdata_free((struct ZlibComprData **) ptr);
}
COMPRESS_OPS(zlib, MIN_COMP_LEVEL, MAX_COMP_LEVEL)
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