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/* Copyright 2013 Google Inc. All Rights Reserved.
Distributed under MIT license.
*/
/* Utilities for building Huffman decoding tables. */
#include "huffman.h"
#include <string.h> /* memcpy, memset */
#include <brotli/types.h>
#include "../common/constants.h"
#include "../common/platform.h"
#if defined(__cplusplus) || defined(c_plusplus)
extern "C" {
#endif
#define BROTLI_REVERSE_BITS_MAX 8
#if defined(BROTLI_RBIT)
#define BROTLI_REVERSE_BITS_BASE \
((sizeof(brotli_reg_t) << 3) - BROTLI_REVERSE_BITS_MAX)
#else
#define BROTLI_REVERSE_BITS_BASE 0
static uint8_t kReverseBits[1 << BROTLI_REVERSE_BITS_MAX] = {
0x00, 0x80, 0x40, 0xC0, 0x20, 0xA0, 0x60, 0xE0,
0x10, 0x90, 0x50, 0xD0, 0x30, 0xB0, 0x70, 0xF0,
0x08, 0x88, 0x48, 0xC8, 0x28, 0xA8, 0x68, 0xE8,
0x18, 0x98, 0x58, 0xD8, 0x38, 0xB8, 0x78, 0xF8,
0x04, 0x84, 0x44, 0xC4, 0x24, 0xA4, 0x64, 0xE4,
0x14, 0x94, 0x54, 0xD4, 0x34, 0xB4, 0x74, 0xF4,
0x0C, 0x8C, 0x4C, 0xCC, 0x2C, 0xAC, 0x6C, 0xEC,
0x1C, 0x9C, 0x5C, 0xDC, 0x3C, 0xBC, 0x7C, 0xFC,
0x02, 0x82, 0x42, 0xC2, 0x22, 0xA2, 0x62, 0xE2,
0x12, 0x92, 0x52, 0xD2, 0x32, 0xB2, 0x72, 0xF2,
0x0A, 0x8A, 0x4A, 0xCA, 0x2A, 0xAA, 0x6A, 0xEA,
0x1A, 0x9A, 0x5A, 0xDA, 0x3A, 0xBA, 0x7A, 0xFA,
0x06, 0x86, 0x46, 0xC6, 0x26, 0xA6, 0x66, 0xE6,
0x16, 0x96, 0x56, 0xD6, 0x36, 0xB6, 0x76, 0xF6,
0x0E, 0x8E, 0x4E, 0xCE, 0x2E, 0xAE, 0x6E, 0xEE,
0x1E, 0x9E, 0x5E, 0xDE, 0x3E, 0xBE, 0x7E, 0xFE,
0x01, 0x81, 0x41, 0xC1, 0x21, 0xA1, 0x61, 0xE1,
0x11, 0x91, 0x51, 0xD1, 0x31, 0xB1, 0x71, 0xF1,
0x09, 0x89, 0x49, 0xC9, 0x29, 0xA9, 0x69, 0xE9,
0x19, 0x99, 0x59, 0xD9, 0x39, 0xB9, 0x79, 0xF9,
0x05, 0x85, 0x45, 0xC5, 0x25, 0xA5, 0x65, 0xE5,
0x15, 0x95, 0x55, 0xD5, 0x35, 0xB5, 0x75, 0xF5,
0x0D, 0x8D, 0x4D, 0xCD, 0x2D, 0xAD, 0x6D, 0xED,
0x1D, 0x9D, 0x5D, 0xDD, 0x3D, 0xBD, 0x7D, 0xFD,
0x03, 0x83, 0x43, 0xC3, 0x23, 0xA3, 0x63, 0xE3,
0x13, 0x93, 0x53, 0xD3, 0x33, 0xB3, 0x73, 0xF3,
0x0B, 0x8B, 0x4B, 0xCB, 0x2B, 0xAB, 0x6B, 0xEB,
0x1B, 0x9B, 0x5B, 0xDB, 0x3B, 0xBB, 0x7B, 0xFB,
0x07, 0x87, 0x47, 0xC7, 0x27, 0xA7, 0x67, 0xE7,
0x17, 0x97, 0x57, 0xD7, 0x37, 0xB7, 0x77, 0xF7,
0x0F, 0x8F, 0x4F, 0xCF, 0x2F, 0xAF, 0x6F, 0xEF,
0x1F, 0x9F, 0x5F, 0xDF, 0x3F, 0xBF, 0x7F, 0xFF
};
#endif /* BROTLI_RBIT */
#define BROTLI_REVERSE_BITS_LOWEST \
((brotli_reg_t)1 << (BROTLI_REVERSE_BITS_MAX - 1 + BROTLI_REVERSE_BITS_BASE))
/* Returns reverse(num >> BROTLI_REVERSE_BITS_BASE, BROTLI_REVERSE_BITS_MAX),
where reverse(value, len) is the bit-wise reversal of the len least
significant bits of value. */
static BROTLI_INLINE brotli_reg_t BrotliReverseBits(brotli_reg_t num) {
#if defined(BROTLI_RBIT)
return BROTLI_RBIT(num);
#else
return kReverseBits[num];
#endif
}
/* Stores code in table[0], table[step], table[2*step], ..., table[end] */
/* Assumes that end is an integer multiple of step */
static BROTLI_INLINE void ReplicateValue(HuffmanCode* table,
int step, int end,
HuffmanCode code) {
do {
end -= step;
table[end] = code;
} while (end > 0);
}
/* Returns the table width of the next 2nd level table. |count| is the histogram
of bit lengths for the remaining symbols, |len| is the code length of the
next processed symbol. */
static BROTLI_INLINE int NextTableBitSize(const uint16_t* const count,
int len, int root_bits) {
int left = 1 << (len - root_bits);
while (len < BROTLI_HUFFMAN_MAX_CODE_LENGTH) {
left -= count[len];
if (left <= 0) break;
++len;
left <<= 1;
}
return len - root_bits;
}
void BrotliBuildCodeLengthsHuffmanTable(HuffmanCode* table,
const uint8_t* const code_lengths,
uint16_t* count) {
HuffmanCode code; /* current table entry */
int symbol; /* symbol index in original or sorted table */
brotli_reg_t key; /* prefix code */
brotli_reg_t key_step; /* prefix code addend */
int step; /* step size to replicate values in current table */
int table_size; /* size of current table */
int sorted[BROTLI_CODE_LENGTH_CODES]; /* symbols sorted by code length */
/* offsets in sorted table for each length */
int offset[BROTLI_HUFFMAN_MAX_CODE_LENGTH_CODE_LENGTH + 1];
int bits;
int bits_count;
BROTLI_DCHECK(BROTLI_HUFFMAN_MAX_CODE_LENGTH_CODE_LENGTH <=
BROTLI_REVERSE_BITS_MAX);
BROTLI_DCHECK(BROTLI_HUFFMAN_MAX_CODE_LENGTH_CODE_LENGTH == 5);
/* Generate offsets into sorted symbol table by code length. */
symbol = -1;
bits = 1;
/* BROTLI_HUFFMAN_MAX_CODE_LENGTH_CODE_LENGTH == 5 */
BROTLI_REPEAT_5({
symbol += count[bits];
offset[bits] = symbol;
bits++;
});
/* Symbols with code length 0 are placed after all other symbols. */
offset[0] = BROTLI_CODE_LENGTH_CODES - 1;
/* Sort symbols by length, by symbol order within each length. */
symbol = BROTLI_CODE_LENGTH_CODES;
do {
BROTLI_REPEAT_6({
symbol--;
sorted[offset[code_lengths[symbol]]--] = symbol;
});
} while (symbol != 0);
table_size = 1 << BROTLI_HUFFMAN_MAX_CODE_LENGTH_CODE_LENGTH;
/* Special case: all symbols but one have 0 code length. */
if (offset[0] == 0) {
code = ConstructHuffmanCode(0, (uint16_t)sorted[0]);
for (key = 0; key < (brotli_reg_t)table_size; ++key) {
table[key] = code;
}
return;
}
/* Fill in table. */
key = 0;
key_step = BROTLI_REVERSE_BITS_LOWEST;
symbol = 0;
bits = 1;
step = 2;
do {
for (bits_count = count[bits]; bits_count != 0; --bits_count) {
code = ConstructHuffmanCode((uint8_t)bits, (uint16_t)sorted[symbol++]);
ReplicateValue(&table[BrotliReverseBits(key)], step, table_size, code);
key += key_step;
}
step <<= 1;
key_step >>= 1;
} while (++bits <= BROTLI_HUFFMAN_MAX_CODE_LENGTH_CODE_LENGTH);
}
uint32_t BrotliBuildHuffmanTable(HuffmanCode* root_table,
int root_bits,
const uint16_t* const symbol_lists,
uint16_t* count) {
HuffmanCode code; /* current table entry */
HuffmanCode* table; /* next available space in table */
int len; /* current code length */
int symbol; /* symbol index in original or sorted table */
brotli_reg_t key; /* prefix code */
brotli_reg_t key_step; /* prefix code addend */
brotli_reg_t sub_key; /* 2nd level table prefix code */
brotli_reg_t sub_key_step; /* 2nd level table prefix code addend */
int step; /* step size to replicate values in current table */
int table_bits; /* key length of current table */
int table_size; /* size of current table */
int total_size; /* sum of root table size and 2nd level table sizes */
int max_length = -1;
int bits;
int bits_count;
BROTLI_DCHECK(root_bits <= BROTLI_REVERSE_BITS_MAX);
BROTLI_DCHECK(BROTLI_HUFFMAN_MAX_CODE_LENGTH - root_bits <=
BROTLI_REVERSE_BITS_MAX);
while (symbol_lists[max_length] == 0xFFFF) max_length--;
max_length += BROTLI_HUFFMAN_MAX_CODE_LENGTH + 1;
table = root_table;
table_bits = root_bits;
table_size = 1 << table_bits;
total_size = table_size;
/* Fill in the root table. Reduce the table size to if possible,
and create the repetitions by memcpy. */
if (table_bits > max_length) {
table_bits = max_length;
table_size = 1 << table_bits;
}
key = 0;
key_step = BROTLI_REVERSE_BITS_LOWEST;
bits = 1;
step = 2;
do {
symbol = bits - (BROTLI_HUFFMAN_MAX_CODE_LENGTH + 1);
for (bits_count = count[bits]; bits_count != 0; --bits_count) {
symbol = symbol_lists[symbol];
code = ConstructHuffmanCode((uint8_t)bits, (uint16_t)symbol);
ReplicateValue(&table[BrotliReverseBits(key)], step, table_size, code);
key += key_step;
}
step <<= 1;
key_step >>= 1;
} while (++bits <= table_bits);
/* If root_bits != table_bits then replicate to fill the remaining slots. */
while (total_size != table_size) {
memcpy(&table[table_size], &table[0],
(size_t)table_size * sizeof(table[0]));
table_size <<= 1;
}
/* Fill in 2nd level tables and add pointers to root table. */
key_step = BROTLI_REVERSE_BITS_LOWEST >> (root_bits - 1);
sub_key = (BROTLI_REVERSE_BITS_LOWEST << 1);
sub_key_step = BROTLI_REVERSE_BITS_LOWEST;
for (len = root_bits + 1, step = 2; len <= max_length; ++len) {
symbol = len - (BROTLI_HUFFMAN_MAX_CODE_LENGTH + 1);
for (; count[len] != 0; --count[len]) {
if (sub_key == (BROTLI_REVERSE_BITS_LOWEST << 1U)) {
table += table_size;
table_bits = NextTableBitSize(count, len, root_bits);
table_size = 1 << table_bits;
total_size += table_size;
sub_key = BrotliReverseBits(key);
key += key_step;
root_table[sub_key] = ConstructHuffmanCode(
(uint8_t)(table_bits + root_bits),
(uint16_t)(((size_t)(table - root_table)) - sub_key));
sub_key = 0;
}
symbol = symbol_lists[symbol];
code = ConstructHuffmanCode((uint8_t)(len - root_bits), (uint16_t)symbol);
ReplicateValue(
&table[BrotliReverseBits(sub_key)], step, table_size, code);
sub_key += sub_key_step;
}
step <<= 1;
sub_key_step >>= 1;
}
return (uint32_t)total_size;
}
uint32_t BrotliBuildSimpleHuffmanTable(HuffmanCode* table,
int root_bits,
uint16_t* val,
uint32_t num_symbols) {
uint32_t table_size = 1;
const uint32_t goal_size = 1U << root_bits;
switch (num_symbols) {
case 0:
table[0] = ConstructHuffmanCode(0, val[0]);
break;
case 1:
if (val[1] > val[0]) {
table[0] = ConstructHuffmanCode(1, val[0]);
table[1] = ConstructHuffmanCode(1, val[1]);
} else {
table[0] = ConstructHuffmanCode(1, val[1]);
table[1] = ConstructHuffmanCode(1, val[0]);
}
table_size = 2;
break;
case 2:
table[0] = ConstructHuffmanCode(1, val[0]);
table[2] = ConstructHuffmanCode(1, val[0]);
if (val[2] > val[1]) {
table[1] = ConstructHuffmanCode(2, val[1]);
table[3] = ConstructHuffmanCode(2, val[2]);
} else {
table[1] = ConstructHuffmanCode(2, val[2]);
table[3] = ConstructHuffmanCode(2, val[1]);
}
table_size = 4;
break;
case 3: {
int i, k;
for (i = 0; i < 3; ++i) {
for (k = i + 1; k < 4; ++k) {
if (val[k] < val[i]) {
uint16_t t = val[k];
val[k] = val[i];
val[i] = t;
}
}
}
table[0] = ConstructHuffmanCode(2, val[0]);
table[2] = ConstructHuffmanCode(2, val[1]);
table[1] = ConstructHuffmanCode(2, val[2]);
table[3] = ConstructHuffmanCode(2, val[3]);
table_size = 4;
break;
}
case 4: {
if (val[3] < val[2]) {
uint16_t t = val[3];
val[3] = val[2];
val[2] = t;
}
table[0] = ConstructHuffmanCode(1, val[0]);
table[1] = ConstructHuffmanCode(2, val[1]);
table[2] = ConstructHuffmanCode(1, val[0]);
table[3] = ConstructHuffmanCode(3, val[2]);
table[4] = ConstructHuffmanCode(1, val[0]);
table[5] = ConstructHuffmanCode(2, val[1]);
table[6] = ConstructHuffmanCode(1, val[0]);
table[7] = ConstructHuffmanCode(3, val[3]);
table_size = 8;
break;
}
}
while (table_size != goal_size) {
memcpy(&table[table_size], &table[0],
(size_t)table_size * sizeof(table[0]));
table_size <<= 1;
}
return goal_size;
}
#if defined(__cplusplus) || defined(c_plusplus)
} /* extern "C" */
#endif