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Add draft specification of the brotli format

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This commit is contained in:
Zoltan Szabadka
2013-11-28 17:37:13 +01:00
parent 4147ca2646
commit fe79fac8da
3 changed files with 1268 additions and 102 deletions
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brotli/enc/encode.cc
+18 -16
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@@ -80,15 +80,15 @@ void EncodeMetaBlockLength(size_t meta_block_size,
int* storage_ix, uint8_t* storage) {
WriteBits(1, 0, storage_ix, storage);
int num_bits = Log2Floor(meta_block_size) + 1;
WriteBits(3, (num_bits + 3) >> 2, storage_ix, storage);
if (num_bits < 16) {
num_bits = 16;
}
WriteBits(2, (num_bits - 13) >> 2, storage_ix, storage);
while (num_bits > 0) {
WriteBits(4, meta_block_size & 0xf, storage_ix, storage);
meta_block_size >>= 4;
num_bits -= 4;
}
if (num_bits > 0) {
WriteBits(num_bits, meta_block_size, storage_ix, storage);
}
}
template<int kSize>
@@ -121,7 +121,7 @@ void StoreHuffmanTreeOfHuffmanTreeToBitMask(
for (int i = skip_two_first * 2; i < codes_to_store; ++i) {
uint8_t len[] = { 2, 4, 3, 2, 2, 4 };
uint8_t bits[] = { 0, 7, 3, 1, 2, 15 };
uint8_t bits[] = { 0, 5, 1, 3, 2, 13 };
int v = code_length_bitdepth[kStorageOrder[i]];
WriteBits(len[v], bits[v], storage_ix, storage);
}
@@ -558,6 +558,12 @@ void BuildAndEncodeBlockSplitCode(const BlockSplit& split,
return;
}
WriteBits(1, 1, storage_ix, storage);
int nbits = Log2Floor(split.num_types_ - 1);
WriteBits(3, nbits, storage_ix, storage);
if (nbits > 0) {
WriteBits(nbits, split.num_types_ - 1 - (1 << nbits), storage_ix, storage);
}
HistogramLiteral type_histo;
for (int i = 0; i < split.type_codes_.size(); ++i) {
type_histo.Add(split.type_codes_[i]);
@@ -570,7 +576,6 @@ void BuildAndEncodeBlockSplitCode(const BlockSplit& split,
}
BuildEntropyCode(length_histo, 15, kNumBlockLenPrefixes,
&code->block_len_code);
WriteBits(8, split.num_types_ - 1, storage_ix, storage);
StoreHuffmanCode(code->block_type_code, split.num_types_ + 2,
storage_ix, storage);
StoreHuffmanCode(code->block_len_code, kNumBlockLenPrefixes,
@@ -769,10 +774,10 @@ BrotliCompressor::BrotliCompressor()
literal_cost_(1 << kRingBufferBits),
storage_ix_(0),
storage_(new uint8_t[2 << kMetaBlockSizeBits]) {
dist_ringbuffer_[0] = 4;
dist_ringbuffer_[1] = 11;
dist_ringbuffer_[2] = 15;
dist_ringbuffer_[3] = 16;
dist_ringbuffer_[0] = 16;
dist_ringbuffer_[1] = 15;
dist_ringbuffer_[2] = 11;
dist_ringbuffer_[3] = 4;
storage_[0] = 0;
}
@@ -782,8 +787,6 @@ BrotliCompressor::~BrotliCompressor() {
}
void BrotliCompressor::WriteStreamHeader() {
// Don't encode input size.
WriteBits(3, 0, &storage_ix_, storage_);
// Encode window size.
if (window_bits_ == 16) {
WriteBits(1, 0, &storage_ix_, storage_);
@@ -828,7 +831,7 @@ void BrotliCompressor::WriteMetaBlock(const size_t input_size,
void BrotliCompressor::FinishStream(
size_t* encoded_size, uint8_t* encoded_buffer) {
WriteBits(1, 1, &storage_ix_, storage_);
WriteBits(2, 0x3, &storage_ix_, storage_);
*encoded_size = (storage_ix_ + 7) >> 3;
memcpy(encoded_buffer, storage_, *encoded_size);
}
@@ -839,9 +842,8 @@ int BrotliCompressBuffer(size_t input_size,
size_t* encoded_size,
uint8_t* encoded_buffer) {
if (input_size == 0) {
encoded_buffer[0] = 1;
encoded_buffer[1] = 0;
*encoded_size = 2;
encoded_buffer[0] = 6;
*encoded_size = 1;
return 1;
}