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#include "deflate.h"
#include "assert.h"
#include "bitstream.h"
#define CM_LENGTH_BITS 4
#define CINFO_LENGTH_BITS 4
#define FCHECK_LENGTH_BITS 5
#define FDICT_LENGTH_BITS 1
#define FLEVEL_LENGTH_BITS 2
bool deflate_decompress(Bitstream *bitstream);
bool zlib_decompress(const uint8_t *compressed_data_buffer,
const size_t compressed_data_length) {
ASSERT(compressed_data_buffer != NULL);
Bitstream bitstream;
Bitstream_init(&bitstream, compressed_data_buffer, compressed_data_length);
uint16_t cm = Bitstream_next_bits(&bitstream, CM_LENGTH_BITS);
uint16_t cinfo = Bitstream_next_bits(&bitstream, CINFO_LENGTH_BITS);
uint16_t fcheck = Bitstream_next_bits(&bitstream, FCHECK_LENGTH_BITS);
uint16_t fdict = Bitstream_next_bits(&bitstream, FDICT_LENGTH_BITS);
uint16_t flevel = Bitstream_next_bits(&bitstream, FLEVEL_LENGTH_BITS);
LOGN("zlib informations:\n"
"- CM (compression method): %d\n"
"- CINFO (compression info): %d\n"
"- FCHECK (check bits for CMF and FLG): %d\n"
"- FDICT (preset dictionary): %d\n"
"- FLEVEL (compression level): %d",
cm, cinfo, fcheck, fdict, flevel);
uint16_t cmf = bitstream.data[0];
uint16_t flg = bitstream.data[1];
if ((cmf * 256 + flg) % 31 != 0) {
LOG0("fcheck validation failed");
return false;
}
uint32_t dictionary_identifier = 0;
if (fdict != 0) {
uint16_t dictionary_identifier_0 = Bitstream_next_bits(&bitstream, 16);
uint16_t dictionary_identifier_1 = Bitstream_next_bits(&bitstream, 16);
dictionary_identifier =
(dictionary_identifier_0 << 0) + (dictionary_identifier_1 << 16);
LOGN("Dictionary identifier: %d", dictionary_identifier);
}
if (!deflate_decompress(&bitstream)) {
return false;
}
// TODO adler32 checksum
return true;
}
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