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// Copyright 2016 The Draco Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
#include "draco/compression/entropy/symbol_decoding.h"
#include <algorithm>
#include <cmath>
#include "draco/compression/entropy/rans_symbol_decoder.h"
namespace draco {
template <template <int> class SymbolDecoderT>
bool DecodeTaggedSymbols(uint32_t num_values, int num_components,
DecoderBuffer *src_buffer, uint32_t *out_values);
template <template <int> class SymbolDecoderT>
bool DecodeRawSymbols(uint32_t num_values, DecoderBuffer *src_buffer,
uint32_t *out_values);
bool DecodeSymbols(uint32_t num_values, int num_components,
DecoderBuffer *src_buffer, uint32_t *out_values) {
if (num_values == 0) {
return true;
}
// Decode which scheme to use.
uint8_t scheme;
if (!src_buffer->Decode(&scheme)) {
return false;
}
if (scheme == SYMBOL_CODING_TAGGED) {
return DecodeTaggedSymbols<RAnsSymbolDecoder>(num_values, num_components,
src_buffer, out_values);
} else if (scheme == SYMBOL_CODING_RAW) {
return DecodeRawSymbols<RAnsSymbolDecoder>(num_values, src_buffer,
out_values);
}
return false;
}
template <template <int> class SymbolDecoderT>
bool DecodeTaggedSymbols(uint32_t num_values, int num_components,
DecoderBuffer *src_buffer, uint32_t *out_values) {
// Decode the encoded data.
SymbolDecoderT<5> tag_decoder;
if (!tag_decoder.Create(src_buffer)) {
return false;
}
if (!tag_decoder.StartDecoding(src_buffer)) {
return false;
}
if (num_values > 0 && tag_decoder.num_symbols() == 0) {
return false; // Wrong number of symbols.
}
// src_buffer now points behind the encoded tag data (to the place where the
// values are encoded).
src_buffer->StartBitDecoding(false, nullptr);
int value_id = 0;
for (uint32_t i = 0; i < num_values; i += num_components) {
// Decode the tag.
const int bit_length = tag_decoder.DecodeSymbol();
// Decode the actual value.
for (int j = 0; j < num_components; ++j) {
uint32_t val;
if (!src_buffer->DecodeLeastSignificantBits32(bit_length, &val)) {
return false;
}
out_values[value_id++] = val;
}
}
tag_decoder.EndDecoding();
src_buffer->EndBitDecoding();
return true;
}
template <class SymbolDecoderT>
bool DecodeRawSymbolsInternal(uint32_t num_values, DecoderBuffer *src_buffer,
uint32_t *out_values) {
SymbolDecoderT decoder;
if (!decoder.Create(src_buffer)) {
return false;
}
if (num_values > 0 && decoder.num_symbols() == 0) {
return false; // Wrong number of symbols.
}
if (!decoder.StartDecoding(src_buffer)) {
return false;
}
for (uint32_t i = 0; i < num_values; ++i) {
// Decode a symbol into the value.
const uint32_t value = decoder.DecodeSymbol();
out_values[i] = value;
}
decoder.EndDecoding();
return true;
}
template <template <int> class SymbolDecoderT>
bool DecodeRawSymbols(uint32_t num_values, DecoderBuffer *src_buffer,
uint32_t *out_values) {
uint8_t max_bit_length;
if (!src_buffer->Decode(&max_bit_length)) {
return false;
}
switch (max_bit_length) {
case 1:
return DecodeRawSymbolsInternal<SymbolDecoderT<1>>(num_values, src_buffer,
out_values);
case 2:
return DecodeRawSymbolsInternal<SymbolDecoderT<2>>(num_values, src_buffer,
out_values);
case 3:
return DecodeRawSymbolsInternal<SymbolDecoderT<3>>(num_values, src_buffer,
out_values);
case 4:
return DecodeRawSymbolsInternal<SymbolDecoderT<4>>(num_values, src_buffer,
out_values);
case 5:
return DecodeRawSymbolsInternal<SymbolDecoderT<5>>(num_values, src_buffer,
out_values);
case 6:
return DecodeRawSymbolsInternal<SymbolDecoderT<6>>(num_values, src_buffer,
out_values);
case 7:
return DecodeRawSymbolsInternal<SymbolDecoderT<7>>(num_values, src_buffer,
out_values);
case 8:
return DecodeRawSymbolsInternal<SymbolDecoderT<8>>(num_values, src_buffer,
out_values);
case 9:
return DecodeRawSymbolsInternal<SymbolDecoderT<9>>(num_values, src_buffer,
out_values);
case 10:
return DecodeRawSymbolsInternal<SymbolDecoderT<10>>(
num_values, src_buffer, out_values);
case 11:
return DecodeRawSymbolsInternal<SymbolDecoderT<11>>(
num_values, src_buffer, out_values);
case 12:
return DecodeRawSymbolsInternal<SymbolDecoderT<12>>(
num_values, src_buffer, out_values);
case 13:
return DecodeRawSymbolsInternal<SymbolDecoderT<13>>(
num_values, src_buffer, out_values);
case 14:
return DecodeRawSymbolsInternal<SymbolDecoderT<14>>(
num_values, src_buffer, out_values);
case 15:
return DecodeRawSymbolsInternal<SymbolDecoderT<15>>(
num_values, src_buffer, out_values);
case 16:
return DecodeRawSymbolsInternal<SymbolDecoderT<16>>(
num_values, src_buffer, out_values);
case 17:
return DecodeRawSymbolsInternal<SymbolDecoderT<17>>(
num_values, src_buffer, out_values);
case 18:
return DecodeRawSymbolsInternal<SymbolDecoderT<18>>(
num_values, src_buffer, out_values);
default:
return false;
}
}
} // namespace draco
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