Edit
kc3-lang/brotli/c/enc/compound_dictionary.c
Eugene Kliuchnikov
- c/enc/compound_dictionary.c
-
/* 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 <brotli/types.h> #include "../common/platform.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_ref = 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) + sizeof(uint8_t*); 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_ref = (uint8_t**)(&items[total_items]); result->magic = kLeanPreparedDictionaryMagic; result->num_items = total_items; result->source_size = (uint32_t)source_size; result->hash_bits = hash_bits; result->bucket_bits = bucket_bits; result->slot_bits = slot_bits; BROTLI_UNALIGNED_STORE_PTR(source_ref, source); 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); 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]); const void* tail = (void*)&items[dictionary->num_items]; if (dictionary->magic == kPreparedDictionaryMagic) { compound->chunk_source[index] = (const uint8_t*)tail; } else { /* dictionary->magic == kLeanPreparedDictionaryMagic */ compound->chunk_source[index] = (const uint8_t*)BROTLI_UNALIGNED_LOAD_PTR((const uint8_t**)tail); } } compound->num_chunks++; return BROTLI_TRUE; }