/* Stores a number between 0 and 255. */
static void StoreVarLenUint8(size_t n, size_t* storage_ix, uint8_t* storage) {
if (n == 0) {
BrotliWriteBits(1, 0, storage_ix, storage);
} else {
size_t nbits = Log2FloorNonZero(n);
BrotliWriteBits(1, 1, storage_ix, storage);
BrotliWriteBits(3, nbits, storage_ix, storage);
BrotliWriteBits(nbits, n - ((size_t)1 << nbits), storage_ix, storage);
}
}
static void BrotliStoreHuffmanTreeOfHuffmanTreeToBitMask(
const int num_codes, const uint8_t* code_length_bitdepth,
size_t* storage_ix, uint8_t* storage) {
static const uint8_t kStorageOrder[BROTLI_CODE_LENGTH_CODES] = {
1, 2, 3, 4, 0, 5, 17, 6, 16, 7, 8, 9, 10, 11, 12, 13, 14, 15
};
/* The bit lengths of the Huffman code over the code length alphabet
are compressed with the following static Huffman code:
Symbol Code
------ ----
0 00
1 1110
2 110
3 01
4 10
5 1111 */
static const uint8_t kHuffmanBitLengthHuffmanCodeSymbols[6] = {
0, 7, 3, 2, 1, 15
};
static const uint8_t kHuffmanBitLengthHuffmanCodeBitLengths[6] = {
2, 4, 3, 2, 2, 4
};
size_t skip_some = 0; /* skips none. */
/* Throw away trailing zeros: */
size_t codes_to_store = BROTLI_CODE_LENGTH_CODES;
if (num_codes > 1) {
for (; codes_to_store > 0; --codes_to_store) {
if (code_length_bitdepth[kStorageOrder[codes_to_store - 1]] != 0) {
break;
}
}
}
if (code_length_bitdepth[kStorageOrder[0]] == 0 &&
code_length_bitdepth[kStorageOrder[1]] == 0) {
skip_some = 2; /* skips two. */
if (code_length_bitdepth[kStorageOrder[2]] == 0) {
skip_some = 3; /* skips three. */
}
}
BrotliWriteBits(2, skip_some, storage_ix, storage);
{
size_t i;
for (i = skip_some; i < codes_to_store; ++i) {
size_t l = code_length_bitdepth[kStorageOrder[i]];
BrotliWriteBits(kHuffmanBitLengthHuffmanCodeBitLengths[l],
kHuffmanBitLengthHuffmanCodeSymbols[l], storage_ix, storage);
}
}
}
/* Stores the uncompressed meta-block header.
REQUIRES: length > 0
REQUIRES: length <= (1 << 24) */
static void BrotliStoreUncompressedMetaBlockHeader(size_t length,
size_t* storage_ix,
uint8_t* storage) {
uint64_t lenbits;
size_t nlenbits;
uint64_t nibblesbits;
/* Write ISLAST bit.
Uncompressed block cannot be the last one, so set to 0. */
BrotliWriteBits(1, 0, storage_ix, storage);
BrotliEncodeMlen(length, &lenbits, &nlenbits, &nibblesbits);
BrotliWriteBits(2, nibblesbits, storage_ix, storage);
BrotliWriteBits(nlenbits, lenbits, storage_ix, storage);
/* Write ISUNCOMPRESSED bit. */
BrotliWriteBits(1, 1, storage_ix, storage);
}
/* REQUIRES: insertlen < 6210 */
static BROTLI_INLINE void EmitInsertLen(size_t insertlen,
const uint8_t depth[128],
const uint16_t bits[128],
uint32_t histo[128],
size_t* storage_ix,
uint8_t* storage) {
if (insertlen < 6) {
const size_t code = insertlen + 40;
BrotliWriteBits(depth[code], bits[code], storage_ix, storage);
++histo[code];
} else if (insertlen < 130) {
const size_t tail = insertlen - 2;
const uint32_t nbits = Log2FloorNonZero(tail) - 1u;
const size_t prefix = tail >> nbits;
const size_t inscode = (nbits << 1) + prefix + 42;
BrotliWriteBits(depth[inscode], bits[inscode], storage_ix, storage);
BrotliWriteBits(nbits, tail - (prefix << nbits), storage_ix, storage);
++histo[inscode];
} else if (insertlen < 2114) {
static BROTLI_INLINE void StoreCommandExtra(
const Command* cmd, size_t* storage_ix, uint8_t* storage) {
uint32_t copylen_code = CommandCopyLenCode(cmd);
uint16_t inscode = GetInsertLengthCode(cmd->insert_len_);
uint16_t copycode = GetCopyLengthCode(copylen_code);
uint32_t insnumextra = GetInsertExtra(inscode);
uint64_t insextraval = cmd->insert_len_ - GetInsertBase(inscode);
uint64_t copyextraval = copylen_code - GetCopyBase(copycode);
uint64_t bits = (copyextraval << insnumextra) | insextraval;
BrotliWriteBits(
insnumextra + GetCopyExtra(copycode), bits, storage_ix, storage);
}
/* Stores the compressed meta-block header.
REQUIRES: length > 0
REQUIRES: length <= (1 << 24) */
static void StoreCompressedMetaBlockHeader(BROTLI_BOOL is_final_block,
size_t length,
size_t* storage_ix,
uint8_t* storage) {
uint64_t lenbits;
size_t nlenbits;
uint64_t nibblesbits;
/* Write ISLAST bit. */
BrotliWriteBits(1, (uint64_t)is_final_block, storage_ix, storage);
/* Write ISEMPTY bit. */
if (is_final_block) {
BrotliWriteBits(1, 0, storage_ix, storage);
}
BrotliEncodeMlen(length, &lenbits, &nlenbits, &nibblesbits);
BrotliWriteBits(2, nibblesbits, storage_ix, storage);
BrotliWriteBits(nlenbits, lenbits, storage_ix, storage);
if (!is_final_block) {
/* Write ISUNCOMPRESSED bit. */
BrotliWriteBits(1, 0, storage_ix, storage);
}
}
