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/*
* Copyright (C) 2017 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.
*/
#ifndef ART_DEX2OAT_LINKER_INDEX_BSS_MAPPING_ENCODER_H_
#define ART_DEX2OAT_LINKER_INDEX_BSS_MAPPING_ENCODER_H_
#include <android-base/logging.h>
#include "base/bit_utils.h"
#include "base/bit_vector-inl.h"
#include "oat/index_bss_mapping.h"
namespace art {
namespace linker {
// Helper class for encoding compressed IndexBssMapping.
class IndexBssMappingEncoder {
public:
IndexBssMappingEncoder(size_t number_of_indexes, size_t slot_size)
: index_bits_(IndexBssMappingEntry::IndexBits(number_of_indexes)),
slot_size_(slot_size) {
entry_.index_and_mask = static_cast<uint32_t>(-1);
entry_.bss_offset = static_cast<uint32_t>(-1);
DCHECK_NE(number_of_indexes, 0u);
}
// Try to merge the next index -> bss_offset mapping into the current entry.
// Return true on success, false on failure.
bool TryMerge(uint32_t index, uint32_t bss_offset) {
DCHECK_LE(MinimumBitsToStore(index), index_bits_);
DCHECK_NE(index, entry_.GetIndex(index_bits_));
if (entry_.bss_offset + slot_size_ != bss_offset) {
return false;
}
uint32_t diff = index - entry_.GetIndex(index_bits_);
if (diff > 32u - index_bits_) {
return false;
}
uint32_t mask = entry_.GetMask(index_bits_);
if ((mask & ~(static_cast<uint32_t>(-1) << diff)) != 0u) {
return false;
}
// Insert the bit indicating the index we've just overwritten
// and shift bits indicating indexes before that.
mask = ((mask << index_bits_) >> diff) | (static_cast<uint32_t>(1u) << (32 - diff));
entry_.index_and_mask = mask | index;
entry_.bss_offset = bss_offset;
return true;
}
void Reset(uint32_t method_index, uint32_t bss_offset) {
DCHECK_LE(MinimumBitsToStore(method_index), index_bits_);
entry_.index_and_mask = method_index; // Mask bits set to 0.
entry_.bss_offset = bss_offset;
}
IndexBssMappingEntry GetEntry() {
return entry_;
}
size_t GetIndexBits() const {
return index_bits_;
}
private:
const size_t index_bits_;
const size_t slot_size_;
IndexBssMappingEntry entry_;
};
} // namespace linker
} // namespace art
#endif // ART_DEX2OAT_LINKER_INDEX_BSS_MAPPING_ENCODER_H_