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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_LIBDEXFILE_DEX_COMPACT_DEX_FILE_H_
#define ART_LIBDEXFILE_DEX_COMPACT_DEX_FILE_H_
#include "base/casts.h"
#include "dex_file.h"
#include "dex/compact_offset_table.h"
namespace art {
// CompactDex is a currently ART internal dex file format that aims to reduce storage/RAM usage.
class CompactDexFile : public DexFile {
public:
static constexpr uint8_t kDexMagic[kDexMagicSize] = { 'c', 'd', 'e', 'x' };
static constexpr uint8_t kDexMagicVersion[] = {'0', '0', '1', '\0'};
enum class FeatureFlags : uint32_t {
kDefaultMethods = 0x1,
};
class Header : public DexFile::Header {
public:
static const Header* At(const void* at) {
return reinterpret_cast<const Header*>(at);
}
uint32_t GetFeatureFlags() const {
return feature_flags_;
}
uint32_t GetDataOffset() const {
return data_off_;
}
uint32_t GetDataSize() const {
return data_size_;
}
// Range of the shared data section owned by the dex file. Owned in this context refers to data
// for this DEX that was not deduplicated to another DEX.
uint32_t OwnedDataBegin() const {
return owned_data_begin_;
}
uint32_t OwnedDataEnd() const {
return owned_data_end_;
}
private:
uint32_t feature_flags_ = 0u;
// Position in the compact dex file for the debug info table data starts.
uint32_t debug_info_offsets_pos_ = 0u;
// Offset into the debug info table data where the lookup table is.
uint32_t debug_info_offsets_table_offset_ = 0u;
// Base offset of where debug info starts in the dex file.
uint32_t debug_info_base_ = 0u;
// Range of the shared data section owned by the dex file.
uint32_t owned_data_begin_ = 0u;
uint32_t owned_data_end_ = 0u;
friend class CompactDexFile;
friend class CompactDexWriter;
};
// Like the standard code item except without a debug info offset. Each code item may have a
// preheader to encode large methods. In 99% of cases, the preheader is not used. This enables
// smaller size with a good fast path case in the accessors.
struct CodeItem : public DexFile::CodeItem {
static constexpr size_t kAlignment = sizeof(uint16_t);
// Max preheader size in uint16_ts.
static constexpr size_t kMaxPreHeaderSize = 6;
private:
CodeItem() = default;
static constexpr size_t kRegistersSizeShift = 12;
static constexpr size_t kInsSizeShift = 8;
static constexpr size_t kOutsSizeShift = 4;
static constexpr size_t kTriesSizeSizeShift = 0;
static constexpr uint16_t kFlagPreHeaderRegisterSize = 0x1 << 0;
static constexpr uint16_t kFlagPreHeaderInsSize = 0x1 << 1;
static constexpr uint16_t kFlagPreHeaderOutsSize = 0x1 << 2;
static constexpr uint16_t kFlagPreHeaderTriesSize = 0x1 << 3;
static constexpr uint16_t kFlagPreHeaderInsnsSize = 0x1 << 4;
static constexpr size_t kInsnsSizeShift = 5;
static constexpr size_t kInsnsSizeBits = sizeof(uint16_t) * kBitsPerByte - kInsnsSizeShift;
// Combined preheader flags for fast testing if we need to go slow path.
static constexpr uint16_t kFlagPreHeaderCombined =
kFlagPreHeaderRegisterSize |
kFlagPreHeaderInsSize |
kFlagPreHeaderOutsSize |
kFlagPreHeaderTriesSize |
kFlagPreHeaderInsnsSize;
// Create a code item and associated preheader if required based on field values.
// Returns the start of the preheader. The preheader buffer must be at least as large as
// kMaxPreHeaderSize;
uint16_t* Create(uint16_t registers_size,
uint16_t ins_size,
uint16_t outs_size,
uint16_t tries_size,
uint32_t insns_size_in_code_units,
uint16_t* out_preheader) {
// Dex verification ensures that registers size > ins_size, so we can subtract the registers
// size accordingly to reduce how often we need to use the preheader.
DCHECK_GE(registers_size, ins_size);
registers_size -= ins_size;
fields_ = (registers_size & 0xF) << kRegistersSizeShift;
fields_ |= (ins_size & 0xF) << kInsSizeShift;
fields_ |= (outs_size & 0xF) << kOutsSizeShift;
fields_ |= (tries_size & 0xF) << kTriesSizeSizeShift;
registers_size &= ~0xF;
ins_size &= ~0xF;
outs_size &= ~0xF;
tries_size &= ~0xF;
insns_count_and_flags_ = 0;
const size_t masked_count = insns_size_in_code_units & ((1 << kInsnsSizeBits) - 1);
insns_count_and_flags_ |= masked_count << kInsnsSizeShift;
insns_size_in_code_units -= masked_count;
// Since the preheader case is rare (1% of code items), use a suboptimally large but fast
// decoding format.
if (insns_size_in_code_units != 0) {
insns_count_and_flags_ |= kFlagPreHeaderInsnsSize;
--out_preheader;
*out_preheader = static_cast<uint16_t>(insns_size_in_code_units);
--out_preheader;
*out_preheader = static_cast<uint16_t>(insns_size_in_code_units >> 16);
}
auto preheader_encode = [&](uint16_t size, uint16_t flag) {
if (size != 0) {
insns_count_and_flags_ |= flag;
--out_preheader;
*out_preheader = size;
}
};
preheader_encode(registers_size, kFlagPreHeaderRegisterSize);
preheader_encode(ins_size, kFlagPreHeaderInsSize);
preheader_encode(outs_size, kFlagPreHeaderOutsSize);
preheader_encode(tries_size, kFlagPreHeaderTriesSize);
return out_preheader;
}
ALWAYS_INLINE bool HasPreHeader(uint16_t flag) const {
return (insns_count_and_flags_ & flag) != 0;
}
// Return true if the code item has any preheaders.
ALWAYS_INLINE static bool HasAnyPreHeader(uint16_t insns_count_and_flags) {
return (insns_count_and_flags & kFlagPreHeaderCombined) != 0;
}
ALWAYS_INLINE uint16_t* GetPreHeader() {
return reinterpret_cast<uint16_t*>(this);
}
ALWAYS_INLINE const uint16_t* GetPreHeader() const {
return reinterpret_cast<const uint16_t*>(this);
}
// Decode fields and read the preheader if necessary. If kDecodeOnlyInstructionCount is
// specified then only the instruction count is decoded.
template <bool kDecodeOnlyInstructionCount>
ALWAYS_INLINE void DecodeFields(uint32_t* insns_count,
uint16_t* registers_size,
uint16_t* ins_size,
uint16_t* outs_size,
uint16_t* tries_size) const {
*insns_count = insns_count_and_flags_ >> kInsnsSizeShift;
if (!kDecodeOnlyInstructionCount) {
const uint16_t fields = fields_;
*registers_size = (fields >> kRegistersSizeShift) & 0xF;
*ins_size = (fields >> kInsSizeShift) & 0xF;
*outs_size = (fields >> kOutsSizeShift) & 0xF;
*tries_size = (fields >> kTriesSizeSizeShift) & 0xF;
}
if (UNLIKELY(HasAnyPreHeader(insns_count_and_flags_))) {
const uint16_t* preheader = GetPreHeader();
if (HasPreHeader(kFlagPreHeaderInsnsSize)) {
--preheader;
*insns_count += static_cast<uint32_t>(*preheader);
--preheader;
*insns_count += static_cast<uint32_t>(*preheader) << 16;
}
if (!kDecodeOnlyInstructionCount) {
if (HasPreHeader(kFlagPreHeaderRegisterSize)) {
--preheader;
*registers_size += preheader[0];
}
if (HasPreHeader(kFlagPreHeaderInsSize)) {
--preheader;
*ins_size += preheader[0];
}
if (HasPreHeader(kFlagPreHeaderOutsSize)) {
--preheader;
*outs_size += preheader[0];
}
if (HasPreHeader(kFlagPreHeaderTriesSize)) {
--preheader;
*tries_size += preheader[0];
}
}
}
if (!kDecodeOnlyInstructionCount) {
*registers_size += *ins_size;
}
}
// Packed code item data, 4 bits each: [registers_size, ins_size, outs_size, tries_size]
uint16_t fields_;
// 5 bits for if either of the fields required preheader extension, 11 bits for the number of
// instruction code units.
uint16_t insns_count_and_flags_;
uint16_t insns_[1]; // actual array of bytecode.
ART_FRIEND_TEST(CodeItemAccessorsTest, TestDexInstructionsAccessor);
ART_FRIEND_TEST(CompactDexFileTest, CodeItemFields);
friend class CodeItemDataAccessor;
friend class CodeItemDebugInfoAccessor;
friend class CodeItemInstructionAccessor;
friend class CompactDexFile;
friend class CompactDexWriter;
DISALLOW_COPY_AND_ASSIGN(CodeItem);
};
// Write the compact dex specific magic.
static void WriteMagic(uint8_t* magic);
// Write the current version, note that the input is the address of the magic.
static void WriteCurrentVersion(uint8_t* magic);
// Returns true if the byte string points to the magic value.
static bool IsMagicValid(const uint8_t* magic);
bool IsMagicValid() const override;
// Returns true if the byte string after the magic is the correct value.
static bool IsVersionValid(const uint8_t* magic);
bool IsVersionValid() const override;
// TODO This is completely a guess. We really need to do better. b/72402467
// We ask for 64 megabytes which should be big enough for any realistic dex file.
size_t GetDequickenedSize() const override {
return 64 * MB;
}
const Header& GetHeader() const {
return down_cast<const Header&>(DexFile::GetHeader());
}
bool SupportsDefaultMethods() const override;
uint32_t GetCodeItemSize(const DexFile::CodeItem& item) const override;
uint32_t GetDebugInfoOffset(uint32_t dex_method_index) const {
return debug_info_offsets_.GetOffset(dex_method_index);
}
static uint32_t CalculateChecksum(const uint8_t* base_begin,
size_t base_size,
const uint8_t* data_begin,
size_t data_size);
uint32_t CalculateChecksum() const override;
private:
CompactDexFile(const uint8_t* base,
size_t size,
const uint8_t* data_begin,
size_t data_size,
const std::string& location,
uint32_t location_checksum,
const OatDexFile* oat_dex_file,
std::unique_ptr<DexFileContainer> container);
CompactOffsetTable::Accessor debug_info_offsets_;
friend class DexFile;
friend class DexFileLoader;
DISALLOW_COPY_AND_ASSIGN(CompactDexFile);
};
} // namespace art
#endif // ART_LIBDEXFILE_DEX_COMPACT_DEX_FILE_H_