zlib.c

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#include "config.h"
#include <stddef.h>
#include <stdint.h>
#include <zconf.h>
#include <zlib.h>
#include "private.h"
#include "mutt/lib.h"
#include "lib.h"
 
#define MIN_COMP_LEVEL 1 
#define MAX_COMP_LEVEL 9 

struct ZlibComprData
{
  void *buf;   
  short level; 
};

void zlib_cdata_free(struct ZlibComprData **ptr)
{
  if (!ptr || !*ptr)
    return;
 
  struct ZlibComprData *cdata = *ptr;
  FREE(&cdata->buf);
 
  FREE(ptr);
}

static struct ZlibComprData *zlib_cdata_new(void)
{
  return MUTT_MEM_CALLOC(1, struct ZlibComprData);
}

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;
}

static void *compr_zlib_compress(ComprHandle *handle, const char *data,
                                 size_t dlen, size_t *clen)
{
  if (!handle || (dlen > UINT32_MAX))
    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;
}

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;
}

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)