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/* Copyright 2017 Google Inc. All Rights Reserved.
Distributed under MIT license.
See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
*/
#include "compound_dictionary.h"
#include "../common/platform.h"
#include <brotli/types.h>
#include "memory.h"
#include "quality.h"
static PreparedDictionary* CreatePreparedDictionaryWithParams(MemoryManager* m,
const uint8_t* source, size_t source_size, uint32_t bucket_bits,
uint32_t slot_bits, uint32_t hash_bits, uint16_t bucket_limit) {
/* Step 1: create "bloated" hasher. */
uint32_t num_slots = 1u << slot_bits;
uint32_t num_buckets = 1u << bucket_bits;
uint32_t hash_shift = 64u - bucket_bits;
uint64_t hash_mask = (~((uint64_t)0U)) >> (64 - hash_bits);
uint32_t slot_mask = num_slots - 1;
size_t alloc_size = (sizeof(uint32_t) << slot_bits) +
(sizeof(uint32_t) << slot_bits) +
(sizeof(uint16_t) << bucket_bits) +
(sizeof(uint32_t) << bucket_bits) +
(sizeof(uint32_t) * source_size);
uint8_t* flat = NULL;
PreparedDictionary* result = NULL;
uint16_t* num = NULL;
uint32_t* bucket_heads = NULL;
uint32_t* next_bucket = NULL;
uint32_t* slot_offsets = NULL;
uint16_t* heads = NULL;
uint32_t* items = NULL;
uint8_t* source_copy = NULL;
uint32_t i;
uint32_t* slot_size = NULL;
uint32_t* slot_limit = NULL;
uint32_t total_items = 0;
if (slot_bits > 16) return NULL;
if (slot_bits > bucket_bits) return NULL;
if (bucket_bits - slot_bits >= 16) return NULL;
flat = BROTLI_ALLOC(m, uint8_t, alloc_size);
if (BROTLI_IS_OOM(m) || BROTLI_IS_NULL(flat)) return NULL;
slot_size = (uint32_t*)flat;
slot_limit = (uint32_t*)(&slot_size[num_slots]);
num = (uint16_t*)(&slot_limit[num_slots]);
bucket_heads = (uint32_t*)(&num[num_buckets]);
next_bucket = (uint32_t*)(&bucket_heads[num_buckets]);
memset(num, 0, num_buckets * sizeof(num[0]));
/* TODO(eustas): apply custom "store" order. */
for (i = 0; i + 7 < source_size; ++i) {
const uint64_t h = (BROTLI_UNALIGNED_LOAD64LE(&source[i]) & hash_mask) *
kPreparedDictionaryHashMul64Long;
const uint32_t key = (uint32_t)(h >> hash_shift);
uint16_t count = num[key];
next_bucket[i] = (count == 0) ? ((uint32_t)(-1)) : bucket_heads[key];
bucket_heads[key] = i;
count++;
if (count > bucket_limit) count = bucket_limit;
num[key] = count;
}
/* Step 2: find slot limits. */
for (i = 0; i < num_slots; ++i) {
BROTLI_BOOL overflow = BROTLI_FALSE;
slot_limit[i] = bucket_limit;
while (BROTLI_TRUE) {
uint32_t limit = slot_limit[i];
size_t j;
uint32_t count = 0;
overflow = BROTLI_FALSE;
for (j = i; j < num_buckets; j += num_slots) {
uint32_t size = num[j];
/* Last chain may span behind 64K limit; overflow happens only if
we are about to use 0xFFFF+ as item offset. */
if (count >= 0xFFFF) {
overflow = BROTLI_TRUE;
break;
}
if (size > limit) size = limit;
count += size;
}
if (!overflow) {
slot_size[i] = count;
total_items += count;
break;
}
slot_limit[i]--;
}
}
/* Step 3: transfer data to "slim" hasher. */
alloc_size = sizeof(PreparedDictionary) + (sizeof(uint32_t) << slot_bits) +
(sizeof(uint16_t) << bucket_bits) + (sizeof(uint32_t) * total_items) +
source_size;
result = (PreparedDictionary*)BROTLI_ALLOC(m, uint8_t, alloc_size);
if (BROTLI_IS_OOM(m) || BROTLI_IS_NULL(result)) {
BROTLI_FREE(m, flat);
return NULL;
}
slot_offsets = (uint32_t*)(&result[1]);
heads = (uint16_t*)(&slot_offsets[num_slots]);
items = (uint32_t*)(&heads[num_buckets]);
source_copy = (uint8_t*)(&items[total_items]);
result->magic = kPreparedDictionaryMagic;
result->source_offset = total_items;
result->source_size = (uint32_t)source_size;
result->hash_bits = hash_bits;
result->bucket_bits = bucket_bits;
result->slot_bits = slot_bits;
total_items = 0;
for (i = 0; i < num_slots; ++i) {
slot_offsets[i] = total_items;
total_items += slot_size[i];
slot_size[i] = 0;
}
for (i = 0; i < num_buckets; ++i) {
uint32_t slot = i & slot_mask;
uint32_t count = num[i];
uint32_t pos;
size_t j;
size_t cursor = slot_size[slot];
if (count > slot_limit[slot]) count = slot_limit[slot];
if (count == 0) {
heads[i] = 0xFFFF;
continue;
}
heads[i] = (uint16_t)cursor;
cursor += slot_offsets[slot];
slot_size[slot] += count;
pos = bucket_heads[i];
for (j = 0; j < count; j++) {
items[cursor++] = pos;
pos = next_bucket[pos];
}
items[cursor - 1] |= 0x80000000;
}
BROTLI_FREE(m, flat);
memcpy(source_copy, source, source_size);
return result;
}
PreparedDictionary* CreatePreparedDictionary(MemoryManager* m,
const uint8_t* source, size_t source_size) {
uint32_t bucket_bits = 17;
uint32_t slot_bits = 7;
uint32_t hash_bits = 40;
uint16_t bucket_limit = 32;
size_t volume = 16u << bucket_bits;
/* Tune parameters to fit dictionary size. */
while (volume < source_size && bucket_bits < 22) {
bucket_bits++;
slot_bits++;
volume <<= 1;
}
return CreatePreparedDictionaryWithParams(m,
source, source_size, bucket_bits, slot_bits, hash_bits, bucket_limit);
}
void DestroyPreparedDictionary(MemoryManager* m,
PreparedDictionary* dictionary) {
if (!dictionary) return;
BROTLI_FREE(m, dictionary);
}
BROTLI_BOOL AttachPreparedDictionary(
CompoundDictionary* compound, const PreparedDictionary* dictionary) {
size_t length = 0;
size_t index = 0;
if (compound->num_chunks == SHARED_BROTLI_MAX_COMPOUND_DICTS) {
return BROTLI_FALSE;
}
if (!dictionary) return BROTLI_FALSE;
length = dictionary->source_size;
index = compound->num_chunks;
compound->total_size += length;
compound->chunks[index] = dictionary;
compound->chunk_offsets[index + 1] = compound->total_size;
{
uint32_t* slot_offsets = (uint32_t*)(&dictionary[1]);
uint16_t* heads = (uint16_t*)(&slot_offsets[1u << dictionary->slot_bits]);
uint32_t* items = (uint32_t*)(&heads[1u << dictionary->bucket_bits]);
compound->chunk_source[index] =
(const uint8_t*)(&items[dictionary->source_offset]);
}
compound->num_chunks++;
return BROTLI_TRUE;
}
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