134 lines
4.8 KiB
C++
134 lines
4.8 KiB
C++
/*
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* Copyright (C) 2018 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "compact_offset_table.h"
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#include "compact_dex_utils.h"
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#include "base/leb128.h"
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namespace art {
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constexpr size_t CompactOffsetTable::kElementsPerIndex;
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CompactOffsetTable::Accessor::Accessor(const uint8_t* data_begin,
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uint32_t minimum_offset,
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uint32_t table_offset)
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: table_(reinterpret_cast<const uint32_t*>(data_begin + table_offset)),
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minimum_offset_(minimum_offset),
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data_begin_(data_begin) {}
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CompactOffsetTable::Accessor::Accessor(const uint8_t* data_begin)
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: Accessor(data_begin + 2 * sizeof(uint32_t),
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reinterpret_cast<const uint32_t*>(data_begin)[0],
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reinterpret_cast<const uint32_t*>(data_begin)[1]) {}
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uint32_t CompactOffsetTable::Accessor::GetOffset(uint32_t index) const {
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const uint32_t offset = table_[index / kElementsPerIndex];
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const size_t bit_index = index % kElementsPerIndex;
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const uint8_t* block = data_begin_ + offset;
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uint16_t bit_mask = *block;
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++block;
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bit_mask = (bit_mask << kBitsPerByte) | *block;
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++block;
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if ((bit_mask & (1 << bit_index)) == 0) {
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// Bit is not set means the offset is 0.
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return 0u;
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}
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// Trim off the bits above the index we want and count how many bits are set. This is how many
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// lebs we need to decode.
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size_t count = POPCOUNT(static_cast<uintptr_t>(bit_mask) << (kBitsPerIntPtrT - 1 - bit_index));
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DCHECK_GT(count, 0u);
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uint32_t current_offset = minimum_offset_;
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do {
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current_offset += DecodeUnsignedLeb128(&block);
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--count;
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} while (count > 0);
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return current_offset;
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}
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void CompactOffsetTable::Build(const std::vector<uint32_t>& offsets,
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std::vector<uint8_t>* out_data) {
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static constexpr size_t kNumOffsets = 2;
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uint32_t out_offsets[kNumOffsets] = {};
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CompactOffsetTable::Build(offsets, out_data, &out_offsets[0], &out_offsets[1]);
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// Write the offsets at the start of the debug info.
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out_data->insert(out_data->begin(),
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reinterpret_cast<const uint8_t*>(&out_offsets[0]),
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reinterpret_cast<const uint8_t*>(&out_offsets[kNumOffsets]));
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}
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void CompactOffsetTable::Build(const std::vector<uint32_t>& offsets,
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std::vector<uint8_t>* out_data,
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uint32_t* out_min_offset,
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uint32_t* out_table_offset) {
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DCHECK(out_data != nullptr);
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DCHECK(out_data->empty());
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// Calculate the base offset and return it.
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*out_min_offset = std::numeric_limits<uint32_t>::max();
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for (const uint32_t offset : offsets) {
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if (offset != 0u) {
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*out_min_offset = std::min(*out_min_offset, offset);
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}
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}
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// Write the leb blocks and store the important offsets (each kElementsPerIndex elements).
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size_t block_start = 0;
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std::vector<uint32_t> offset_table;
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// Write data first then the table.
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while (block_start < offsets.size()) {
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// Write the offset of the block for each block.
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offset_table.push_back(out_data->size());
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// Block size of up to kElementsPerIndex
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const size_t block_size = std::min(offsets.size() - block_start, kElementsPerIndex);
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// Calculate bit mask since need to write that first.
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uint16_t bit_mask = 0u;
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for (size_t i = 0; i < block_size; ++i) {
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if (offsets[block_start + i] != 0u) {
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bit_mask |= 1 << i;
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}
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}
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// Write bit mask.
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out_data->push_back(static_cast<uint8_t>(bit_mask >> kBitsPerByte));
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out_data->push_back(static_cast<uint8_t>(bit_mask));
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// Write offsets relative to the previous offset.
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uint32_t prev_offset = *out_min_offset;
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for (size_t i = 0; i < block_size; ++i) {
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const uint32_t offset = offsets[block_start + i];
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if (offset != 0u) {
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uint32_t delta = offset - prev_offset;
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EncodeUnsignedLeb128(out_data, delta);
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prev_offset = offset;
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}
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}
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block_start += block_size;
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}
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// Write the offset table.
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AlignmentPadVector(out_data, alignof(uint32_t));
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*out_table_offset = out_data->size();
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out_data->insert(out_data->end(),
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reinterpret_cast<const uint8_t*>(&offset_table[0]),
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reinterpret_cast<const uint8_t*>(&offset_table[0] + offset_table.size()));
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}
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} // namespace art
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