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/*
* Copyright (C) 2018 The Android Open Source Project
*
* 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 "compact_offset_table.h"
#include "compact_dex_utils.h"
#include "base/leb128.h"
namespace art {
constexpr size_t CompactOffsetTable::kElementsPerIndex;
CompactOffsetTable::Accessor::Accessor(const uint8_t* data_begin,
uint32_t minimum_offset,
uint32_t table_offset)
: table_(reinterpret_cast<const uint32_t*>(data_begin + table_offset)),
minimum_offset_(minimum_offset),
data_begin_(data_begin) {}
CompactOffsetTable::Accessor::Accessor(const uint8_t* data_begin)
: Accessor(data_begin + 2 * sizeof(uint32_t),
reinterpret_cast<const uint32_t*>(data_begin)[0],
reinterpret_cast<const uint32_t*>(data_begin)[1]) {}
uint32_t CompactOffsetTable::Accessor::GetOffset(uint32_t index) const {
const uint32_t offset = table_[index / kElementsPerIndex];
const size_t bit_index = index % kElementsPerIndex;
const uint8_t* block = data_begin_ + offset;
uint16_t bit_mask = *block;
++block;
bit_mask = (bit_mask << kBitsPerByte) | *block;
++block;
if ((bit_mask & (1 << bit_index)) == 0) {
// Bit is not set means the offset is 0.
return 0u;
}
// Trim off the bits above the index we want and count how many bits are set. This is how many
// lebs we need to decode.
size_t count = POPCOUNT(static_cast<uintptr_t>(bit_mask) << (kBitsPerIntPtrT - 1 - bit_index));
DCHECK_GT(count, 0u);
uint32_t current_offset = minimum_offset_;
do {
current_offset += DecodeUnsignedLeb128(&block);
--count;
} while (count > 0);
return current_offset;
}
void CompactOffsetTable::Build(const std::vector<uint32_t>& offsets,
std::vector<uint8_t>* out_data) {
static constexpr size_t kNumOffsets = 2;
uint32_t out_offsets[kNumOffsets] = {};
CompactOffsetTable::Build(offsets, out_data, &out_offsets[0], &out_offsets[1]);
// Write the offsets at the start of the debug info.
out_data->insert(out_data->begin(),
reinterpret_cast<const uint8_t*>(&out_offsets[0]),
reinterpret_cast<const uint8_t*>(&out_offsets[kNumOffsets]));
}
void CompactOffsetTable::Build(const std::vector<uint32_t>& offsets,
std::vector<uint8_t>* out_data,
uint32_t* out_min_offset,
uint32_t* out_table_offset) {
DCHECK(out_data != nullptr);
DCHECK(out_data->empty());
// Calculate the base offset and return it.
*out_min_offset = std::numeric_limits<uint32_t>::max();
for (const uint32_t offset : offsets) {
if (offset != 0u) {
*out_min_offset = std::min(*out_min_offset, offset);
}
}
// Write the leb blocks and store the important offsets (each kElementsPerIndex elements).
size_t block_start = 0;
std::vector<uint32_t> offset_table;
// Write data first then the table.
while (block_start < offsets.size()) {
// Write the offset of the block for each block.
offset_table.push_back(out_data->size());
// Block size of up to kElementsPerIndex
const size_t block_size = std::min(offsets.size() - block_start, kElementsPerIndex);
// Calculate bit mask since need to write that first.
uint16_t bit_mask = 0u;
for (size_t i = 0; i < block_size; ++i) {
if (offsets[block_start + i] != 0u) {
bit_mask |= 1 << i;
}
}
// Write bit mask.
out_data->push_back(static_cast<uint8_t>(bit_mask >> kBitsPerByte));
out_data->push_back(static_cast<uint8_t>(bit_mask));
// Write offsets relative to the previous offset.
uint32_t prev_offset = *out_min_offset;
for (size_t i = 0; i < block_size; ++i) {
const uint32_t offset = offsets[block_start + i];
if (offset != 0u) {
uint32_t delta = offset - prev_offset;
EncodeUnsignedLeb128(out_data, delta);
prev_offset = offset;
}
}
block_start += block_size;
}
// Write the offset table.
AlignmentPadVector(out_data, alignof(uint32_t));
*out_table_offset = out_data->size();
out_data->insert(out_data->end(),
reinterpret_cast<const uint8_t*>(&offset_table[0]),
reinterpret_cast<const uint8_t*>(&offset_table[0] + offset_table.size()));
}
} // namespace art
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