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Brotli format change: small improvement to the encoding of Huffman codes

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Combine the HSKIP and the simple/complex Huffman code type bits.
This commit is contained in:
Zoltan Szabadka
2014-01-08 12:28:28 +01:00
parent efbc1a8965
commit 4c8c7fd31c
4 changed files with 32 additions and 25 deletions
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brotli/dec/decode.c
+8 -5
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@@ -234,7 +234,7 @@ static int ReadHuffmanCode(int alphabet_size,
HuffmanTree* tree,
BrotliBitReader* br) {
int ok = 1;
int simple_code;
int simple_code_or_skip;
uint8_t* code_lengths = NULL;
code_lengths =
@@ -247,9 +247,12 @@ static int ReadHuffmanCode(int alphabet_size,
printf("[ReadHuffmanCode] Unexpected end of input.\n");
return 0;
}
simple_code = BrotliReadBits(br, 1);
BROTLI_LOG_UINT(simple_code);
if (simple_code) { /* Read symbols, codes & code lengths directly. */
/* simple_code_or_skip is used as follows:
1 for simple code;
0 for no skipping, 2 skips 2 code lengths, 3 skips 3 code lengths */
simple_code_or_skip = BrotliReadBits(br, 2);
BROTLI_LOG_UINT(simple_code_or_skip);
if (simple_code_or_skip == 1) { /* Read symbols, codes & code lengths directly. */
int i;
int max_bits_counter = alphabet_size - 1;
int max_bits = 0;
@@ -286,7 +289,7 @@ static int ReadHuffmanCode(int alphabet_size,
int i;
uint8_t code_length_code_lengths[CODE_LENGTH_CODES] = { 0 };
int space = 32;
for (i = BrotliReadBits(br, 1) * 2;
for (i = simple_code_or_skip;
i < CODE_LENGTH_CODES && space > 0; ++i) {
int code_len_idx = kCodeLengthCodeOrder[i];
int v = BrotliReadBits(br, 2);