| /* |
| * Copyright (C) 2015 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_TYPE_LOOKUP_TABLE_H_ |
| #define ART_LIBDEXFILE_DEX_TYPE_LOOKUP_TABLE_H_ |
| |
| #include <android-base/logging.h> |
| |
| #include "dex/dex_file_types.h" |
| |
| namespace art { |
| |
| class DexFile; |
| |
| /** |
| * TypeLookupTable used to find class_def_idx by class descriptor quickly. |
| * Implementation of TypeLookupTable is based on hash table. |
| * This class instantiated at compile time by calling Create() method and written into OAT file. |
| * At runtime, the raw data is read from memory-mapped file by calling Open() method. The table |
| * memory remains clean. |
| */ |
| class TypeLookupTable { |
| public: |
| // Method creates lookup table for dex file. |
| static TypeLookupTable Create(const DexFile& dex_file); |
| |
| // Method opens lookup table from binary data. Lookups will traverse strings and other |
| // data contained in dex_file as well. Lookup table does not own raw_data or dex_file. |
| static TypeLookupTable Open(const uint8_t* dex_data_pointer, |
| const uint8_t* raw_data, |
| uint32_t num_class_defs); |
| |
| // Create an invalid lookup table. |
| TypeLookupTable() |
| : dex_data_begin_(nullptr), |
| mask_bits_(0u), |
| entries_(nullptr), |
| owned_entries_(nullptr) {} |
| |
| TypeLookupTable(TypeLookupTable&& src) noexcept = default; |
| TypeLookupTable& operator=(TypeLookupTable&& src) noexcept = default; |
| |
| ~TypeLookupTable() { |
| // Implicit deallocation by std::unique_ptr<> destructor. |
| } |
| |
| // Returns whether the TypeLookupTable is valid. |
| bool Valid() const { |
| return entries_ != nullptr; |
| } |
| |
| // Return the number of buckets in the lookup table. |
| uint32_t Size() const { |
| DCHECK(Valid()); |
| return 1u << mask_bits_; |
| } |
| |
| // Method search class_def_idx by class descriptor and it's hash. |
| // If no data found then the method returns dex::kDexNoIndex. |
| uint32_t Lookup(const char* str, uint32_t hash) const; |
| |
| // Method returns pointer to binary data of lookup table. Used by the oat writer. |
| const uint8_t* RawData() const { |
| DCHECK(Valid()); |
| return reinterpret_cast<const uint8_t*>(entries_); |
| } |
| |
| // Method returns length of binary data. Used by the oat writer. |
| uint32_t RawDataLength() const { |
| DCHECK(Valid()); |
| return Size() * sizeof(Entry); |
| } |
| |
| // Method returns length of binary data for the specified number of class definitions. |
| static uint32_t RawDataLength(uint32_t num_class_defs); |
| |
| void Dump(std::ostream& os) const; |
| |
| private: |
| /** |
| * To find element we need to compare strings. |
| * It is faster to compare first hashes and then strings itself. |
| * But we have no full hash of element of table. But we can use 2 ideas. |
| * 1. All minor bits of hash inside one bucket are equal. |
| * (TODO: We're not actually using this, are we?) |
| * 2. If the dex file contains N classes and the size of the hash table is 2^n (where N <= 2^n) |
| * then we need n bits for the class def index and n bits for the next position delta. |
| * So we can encode part of element's hash into the remaining 32-2*n (n <= 16) bits which |
| * would be otherwise wasted as a padding. |
| * So hash of element can be divided on three parts: |
| * XXXX XXXX XXXY YYYY YYYY YZZZ ZZZZ ZZZZ (example with n=11) |
| * Z - a part of hash encoded implicitly in the bucket index |
| * (these bits are same for all elements in bucket) |
| * Y - a part of hash that we can write into free 32-2*n bits |
| * X - a part of hash that we can't use without increasing the size of the entry |
| * So the `data` element of Entry is used to store the next position delta, class_def_index |
| * and a part of hash of the entry. |
| */ |
| class Entry { |
| public: |
| Entry() : str_offset_(0u), data_(0u) {} |
| Entry(uint32_t str_offset, uint32_t hash, uint32_t class_def_index, uint32_t mask_bits) |
| : str_offset_(str_offset), |
| data_(((hash & ~GetMask(mask_bits)) | class_def_index) << mask_bits) { |
| DCHECK_EQ(class_def_index & ~GetMask(mask_bits), 0u); |
| } |
| |
| void SetNextPosDelta(uint32_t next_pos_delta, uint32_t mask_bits) { |
| DCHECK_EQ(GetNextPosDelta(mask_bits), 0u); |
| DCHECK_EQ(next_pos_delta & ~GetMask(mask_bits), 0u); |
| DCHECK_NE(next_pos_delta, 0u); |
| data_ |= next_pos_delta; |
| } |
| |
| bool IsEmpty() const { |
| return str_offset_ == 0u; |
| } |
| |
| bool IsLast(uint32_t mask_bits) const { |
| return GetNextPosDelta(mask_bits) == 0u; |
| } |
| |
| uint32_t GetStringOffset() const { |
| return str_offset_; |
| } |
| |
| uint32_t GetNextPosDelta(uint32_t mask_bits) const { |
| return data_ & GetMask(mask_bits); |
| } |
| |
| uint32_t GetClassDefIdx(uint32_t mask_bits) const { |
| return (data_ >> mask_bits) & GetMask(mask_bits); |
| } |
| |
| uint32_t GetHashBits(uint32_t mask_bits) const { |
| DCHECK_LE(mask_bits, 16u); |
| return static_cast<uint64_t>(data_) >> (2u * mask_bits); |
| } |
| |
| static uint32_t GetMask(uint32_t mask_bits) { |
| DCHECK_LE(mask_bits, 16u); |
| return ~(std::numeric_limits<uint32_t>::max() << mask_bits); |
| } |
| |
| private: |
| uint32_t str_offset_; |
| uint32_t data_; |
| }; |
| |
| static uint32_t CalculateMaskBits(uint32_t num_class_defs); |
| static bool SupportedSize(uint32_t num_class_defs); |
| |
| // Construct the TypeLookupTable. |
| TypeLookupTable(const uint8_t* dex_data_pointer, |
| uint32_t mask_bits, |
| const Entry* entries, |
| std::unique_ptr<Entry[]> owned_entries); |
| |
| const char* GetStringData(const Entry& entry) const; |
| |
| const uint8_t* dex_data_begin_; |
| uint32_t mask_bits_; |
| const Entry* entries_; |
| // `owned_entries_` is either null (not owning `entries_`) or same pointer as `entries_`. |
| std::unique_ptr<Entry[]> owned_entries_; |
| }; |
| |
| } // namespace art |
| |
| #endif // ART_LIBDEXFILE_DEX_TYPE_LOOKUP_TABLE_H_ |