*/ REBSER *Compress(REBSER *input, REBINT index, REBINT len, REBFLG use_crc)
/*
** Compress a binary (only).
** data
** /part
** length
** /crc32
**
** Note: If the file length is "small", it can't overrun on
** compression too much so we use our magic numbers; otherwise,
** we'll just be safe by a percentage of the file size. This may
** be a bit much, though.
**
***********************************************************************/
{
// NOTE: The use_crc flag is not present in Zlib 1.2.8
// Instead, compress's fifth paramter is the compression level
// It can be a value from 1 to 9, or Z_DEFAULT_COMPRESSION if you
// want it to pick what the library author considers the "worth it"
// tradeoff of time to generally suggest.
uLongf size;
REBSER *output;
REBINT err;
REBYTE out_size[sizeof(REBCNT)];
if (len < 0) Trap_DEAD_END(RE_PAST_END); // !!! better msg needed
size = len + (len > STERLINGS_MAGIC_NUMBER ? len / 10 + 12 : STERLINGS_MAGIC_FIX);
output = Make_Binary(size);
//DISABLE_GC; // !!! why??
// dest, dest-len, src, src-len, level
err = z_compress2(BIN_HEAD(output), &size, BIN_HEAD(input) + index, len, Z_DEFAULT_COMPRESSION);
if (err) {
REBVAL arg;
if (err == Z_MEM_ERROR) Trap_DEAD_END(RE_NO_MEMORY);
SET_INTEGER(&arg, err);
Trap1_DEAD_END(RE_BAD_PRESS, &arg); //!!!provide error string descriptions
}
SET_STR_END(output, size);
SERIES_TAIL(output) = size;
REBCNT_To_Bytes(out_size, (REBCNT)len); // Tag the size to the end.
Append_Series(output, (REBYTE*)out_size, sizeof(REBCNT));
if (SERIES_AVAIL(output) > 1024) // Is there wasted space?
output = Copy_Series(output); // Trim it down if too big. !!! Revisit this based on mem alloc alg.
//ENABLE_GC;
return output;
}
*/ REBSER *Compress(REBSER *input, REBINT index, REBCNT len, REBFLG gzip, REBFLG raw)
/*
** This is a wrapper over Zlib which will compress a BINARY!
** series to produce another BINARY!. It can use either gzip
** or zlib envelopes, and has a "raw" option for no header.
**
** !!! Adds 32-bit size info to zlib non-raw compressions for
** compatibility with Rebol2 and R3-Alpha, at the cost of
** inventing yet-another-format. Consider removing.
**
** !!! Does not expose the "streaming" ability of zlib.
**
***********************************************************************/
{
REBCNT buf_size;
REBSER *output;
int ret;
z_stream strm;
assert(BYTE_SIZE(input)); // must be BINARY!
// compression level can be a value from 1 to 9, or Z_DEFAULT_COMPRESSION
// if you want it to pick what the library author considers the "worth it"
// tradeoff of time to generally suggest.
//
strm.zalloc = Z_NULL;
strm.zfree = Z_NULL;
strm.opaque = Z_NULL;
ret = deflateInit2(
&strm,
Z_DEFAULT_COMPRESSION,
Z_DEFLATED,
raw
? (gzip ? window_bits_gzip_raw : window_bits_zlib_raw)
: (gzip ? window_bits_gzip : window_bits_zlib),
8,
Z_DEFAULT_STRATEGY
);
if (ret != Z_OK)
raise Error_Compression(&strm, ret);
// http://stackoverflow.com/a/4938401/211160
buf_size = deflateBound(&strm, len);
strm.avail_in = len;
strm.next_in = BIN_HEAD(input) + index;
output = Make_Binary(buf_size);
strm.avail_out = buf_size;
strm.next_out = BIN_HEAD(output);
ret = deflate(&strm, Z_FINISH);
deflateEnd(&strm);
if (ret != Z_STREAM_END)
raise Error_Compression(&strm, ret);
SET_STR_END(output, buf_size - strm.avail_out);
SERIES_TAIL(output) = buf_size - strm.avail_out;
if (gzip) {
// GZIP contains its own CRC. It also has a 32-bit uncompressed
// length (and CRC), conveniently (and perhaps confusingly) at the
// tail in the same format that Rebol used.
REBCNT gzip_len = Bytes_To_REBCNT(
SERIES_DATA(output) + buf_size - strm.avail_out - sizeof(REBCNT)
);
assert(len == gzip_len);
}
else if (!raw) {
// Add 32-bit length to the end.
//
// !!! In ZLIB format the length can be found by decompressing, but
// not known a priori. So this is for efficiency. It would likely be
// better to not include this as it only confuses matters for those
// expecting the data to be in a known format...though it means that
// clients who wanted to decompress to a known allocation size would
// have to save the size somewhere.
REBYTE out_size[sizeof(REBCNT)];
REBCNT_To_Bytes(out_size, cast(REBCNT, len));
Append_Series(output, cast(REBYTE*, out_size), sizeof(REBCNT));
}
