dexlayout/compact_dex_writer.cc - platform/art - Git at Google

 /*
  * 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.
  */

 #include "compact_dex_writer.h"

 #include "android-base/stringprintf.h"
 #include "base/logging.h"
 #include "base/time_utils.h"
 #include "dex/compact_dex_file.h"
 #include "dex/compact_offset_table.h"
 #include "dexlayout.h"

 namespace art {

 CompactDexWriter::CompactDexWriter(DexLayout* dex_layout)
     : DexWriter(dex_layout, /*compute_offsets=*/ true) {
   CHECK(GetCompactDexLevel() != CompactDexLevel::kCompactDexLevelNone);
 }

 CompactDexLevel CompactDexWriter::GetCompactDexLevel() const {
   return dex_layout_->GetOptions().compact_dex_level_;
 }

 CompactDexWriter::Container::Container(bool dedupe_code_items)
     : code_item_dedupe_(dedupe_code_items, &data_section_),
       data_item_dedupe_(/*enabled=*/ true, &data_section_) {}

 uint32_t CompactDexWriter::WriteDebugInfoOffsetTable(Stream* stream) {
   const uint32_t start_offset = stream->Tell();
   // Debug offsets for method indexes. 0 means no debug info.
   std::vector<uint32_t> debug_info_offsets(header_->MethodIds().Size(), 0u);

   static constexpr InvokeType invoke_types[] = {
     kDirect,
     kVirtual
   };

   for (InvokeType invoke_type : invoke_types) {
     for (auto& class_def : header_->ClassDefs()) {
       // Skip classes that are not defined in this dex file.
       dex_ir::ClassData* class_data = class_def->GetClassData();
       if (class_data == nullptr) {
         continue;
       }
       for (auto& method : *(invoke_type == InvokeType::kDirect
                                 ? class_data->DirectMethods()
                                 : class_data->VirtualMethods())) {
         const dex_ir::MethodId* method_id = method.GetMethodId();
         dex_ir::CodeItem* code_item = method.GetCodeItem();
         if (code_item != nullptr && code_item->DebugInfo() != nullptr) {
           const uint32_t debug_info_offset = code_item->DebugInfo()->GetOffset();
           const uint32_t method_idx = method_id->GetIndex();
           if (debug_info_offsets[method_idx] != 0u) {
             CHECK_EQ(debug_info_offset, debug_info_offsets[method_idx]);
           }
           debug_info_offsets[method_idx] = debug_info_offset;
         }
       }
     }
   }

   std::vector<uint8_t> data;
   debug_info_base_ = 0u;
   debug_info_offsets_table_offset_ = 0u;
   CompactOffsetTable::Build(debug_info_offsets,
                             &data,
                             &debug_info_base_,
                             &debug_info_offsets_table_offset_);
   // Align the table and write it out.
   stream->AlignTo(CompactOffsetTable::kAlignment);
   debug_info_offsets_pos_ = stream->Tell();
   stream->Write(data.data(), data.size());

   // Verify that the whole table decodes as expected and measure average performance.
   const bool kMeasureAndTestOutput = dex_layout_->GetOptions().verify_output_;
   if (kMeasureAndTestOutput && !debug_info_offsets.empty()) {
     uint64_t start_time = NanoTime();
     stream->Begin();
     CompactOffsetTable::Accessor accessor(stream->Begin() + debug_info_offsets_pos_,
                                           debug_info_base_,
                                           debug_info_offsets_table_offset_);

     for (size_t i = 0; i < debug_info_offsets.size(); ++i) {
       CHECK_EQ(accessor.GetOffset(i), debug_info_offsets[i]);
     }
     uint64_t end_time = NanoTime();
     VLOG(dex) << "Average lookup time (ns) for debug info offsets: "
               << (end_time - start_time) / debug_info_offsets.size();
   }

   return stream->Tell() - start_offset;
 }

 CompactDexWriter::ScopedDataSectionItem::ScopedDataSectionItem(Stream* stream,
                                                                dex_ir::Item* item,
                                                                size_t alignment,
                                                                Deduper* deduper)
     : stream_(stream),
       item_(item),
       alignment_(alignment),
       deduper_(deduper),
       start_offset_(stream->Tell()) {
   stream_->AlignTo(alignment_);
 }

 CompactDexWriter::ScopedDataSectionItem::~ScopedDataSectionItem() {
   // After having written, maybe dedupe the whole code item (excluding padding).
   const uint32_t deduped_offset = deduper_->Dedupe(start_offset_,
                                                    stream_->Tell(),
                                                    item_->GetOffset());
   // If we deduped, only use the deduped offset if the alignment matches the required alignment.
   // Otherwise, return without deduping.
   if (deduped_offset != Deduper::kDidNotDedupe && IsAlignedParam(deduped_offset, alignment_)) {
     // Update the IR offset to the offset of the deduped item.
     item_->SetOffset(deduped_offset);
     // Clear the written data for the item so that the stream write doesn't abort in the future.
     stream_->Clear(start_offset_, stream_->Tell() - start_offset_);
     // Since we deduped, restore the offset to the original position.
     stream_->Seek(start_offset_);
   }
 }

 size_t CompactDexWriter::ScopedDataSectionItem::Written() const {
   return stream_->Tell() - start_offset_;
 }

 void CompactDexWriter::WriteCodeItem(Stream* stream,
                                      dex_ir::CodeItem* code_item,
                                      bool reserve_only) {
   DCHECK(code_item != nullptr);
   DCHECK(!reserve_only) << "Not supported because of deduping.";
   ScopedDataSectionItem data_item(stream,
                                   code_item,
                                   CompactDexFile::CodeItem::kAlignment,
                                   code_item_dedupe_);

   CompactDexFile::CodeItem disk_code_item;

   uint16_t preheader_storage[CompactDexFile::CodeItem::kMaxPreHeaderSize] = {};
   uint16_t* preheader_end = preheader_storage + CompactDexFile::CodeItem::kMaxPreHeaderSize;
   const uint16_t* preheader = disk_code_item.Create(
       code_item->RegistersSize(),
       code_item->InsSize(),
       code_item->OutsSize(),
       code_item->TriesSize(),
       code_item->InsnsSize(),
       preheader_end);
   const size_t preheader_bytes = (preheader_end - preheader) * sizeof(preheader[0]);

   static constexpr size_t kPayloadInstructionRequiredAlignment = 4;
   const uint32_t current_code_item_start = stream->Tell() + preheader_bytes;
   if (!IsAlignedParam(current_code_item_start, kPayloadInstructionRequiredAlignment) ||
       kIsDebugBuild) {
     // If the preheader is going to make the code unaligned, consider adding 2 bytes of padding
     // before if required.
     IterationRange<DexInstructionIterator> instructions = code_item->Instructions();
     SafeDexInstructionIterator it(instructions.begin(), instructions.end());
     for (; !it.IsErrorState() && it < instructions.end(); ++it) {
       // In case the instruction goes past the end of the code item, make sure to not process it.
       if (std::next(it).IsErrorState()) {
         break;
       }
       const Instruction::Code opcode = it->Opcode();
       // Payload instructions possibly require special alignment for their data.
       if (opcode == Instruction::FILL_ARRAY_DATA ||
           opcode == Instruction::PACKED_SWITCH ||
           opcode == Instruction::SPARSE_SWITCH) {
         stream->Skip(
             RoundUp(current_code_item_start, kPayloadInstructionRequiredAlignment) -
                 current_code_item_start);
         break;
       }
     }
   }

   // Write preheader first.
   stream->Write(reinterpret_cast<const uint8_t*>(preheader), preheader_bytes);
   // Registered offset is after the preheader.
   ProcessOffset(stream, code_item);
   // Avoid using sizeof so that we don't write the fake instruction array at the end of the code
   // item.
   stream->Write(&disk_code_item, OFFSETOF_MEMBER(CompactDexFile::CodeItem, insns_));
   // Write the instructions.
   stream->Write(code_item->Insns(), code_item->InsnsSize() * sizeof(uint16_t));
   // Write the post instruction data.
   WriteCodeItemPostInstructionData(stream, code_item, reserve_only);
 }

 void CompactDexWriter::WriteDebugInfoItem(Stream* stream, dex_ir::DebugInfoItem* debug_info) {
   ScopedDataSectionItem data_item(stream,
                                   debug_info,
                                   SectionAlignment(DexFile::kDexTypeDebugInfoItem),
                                   data_item_dedupe_);
   ProcessOffset(stream, debug_info);
   stream->Write(debug_info->GetDebugInfo(), debug_info->GetDebugInfoSize());
 }


 CompactDexWriter::Deduper::Deduper(bool enabled, DexContainer::Section* section)
     : enabled_(enabled),
       dedupe_map_(/*__n=*/ 32,
                   HashedMemoryRange::HashEqual(section),
                   HashedMemoryRange::HashEqual(section)) {}

 uint32_t CompactDexWriter::Deduper::Dedupe(uint32_t data_start,
                                            uint32_t data_end,
                                            uint32_t item_offset) {
   if (!enabled_) {
     return kDidNotDedupe;
   }
   HashedMemoryRange range {data_start, data_end - data_start};
   auto existing = dedupe_map_.emplace(range, item_offset);
   if (!existing.second) {
     // Failed to insert means we deduped, return the existing item offset.
     return existing.first->second;
   }
   return kDidNotDedupe;
 }

 void CompactDexWriter::SortDebugInfosByMethodIndex() {
   static constexpr InvokeType invoke_types[] = {
     kDirect,
     kVirtual
   };
   std::map<const dex_ir::DebugInfoItem*, uint32_t> method_idx_map;
   for (InvokeType invoke_type : invoke_types) {
     for (auto& class_def : header_->ClassDefs()) {
       // Skip classes that are not defined in this dex file.
       dex_ir::ClassData* class_data = class_def->GetClassData();
       if (class_data == nullptr) {
         continue;
       }
       for (auto& method : *(invoke_type == InvokeType::kDirect
                                 ? class_data->DirectMethods()
                                 : class_data->VirtualMethods())) {
         const dex_ir::MethodId* method_id = method.GetMethodId();
         dex_ir::CodeItem* code_item = method.GetCodeItem();
         if (code_item != nullptr && code_item->DebugInfo() != nullptr) {
           const dex_ir::DebugInfoItem* debug_item = code_item->DebugInfo();
           method_idx_map.insert(std::make_pair(debug_item, method_id->GetIndex()));
         }
       }
     }
   }
   std::sort(header_->DebugInfoItems().begin(),
             header_->DebugInfoItems().end(),
             [&](const std::unique_ptr<dex_ir::DebugInfoItem>& a,
                 const std::unique_ptr<dex_ir::DebugInfoItem>& b) {
     auto it_a = method_idx_map.find(a.get());
     auto it_b = method_idx_map.find(b.get());
     uint32_t idx_a = it_a != method_idx_map.end() ? it_a->second : 0u;
     uint32_t idx_b = it_b != method_idx_map.end() ? it_b->second : 0u;
     return idx_a < idx_b;
   });
 }

 void CompactDexWriter::WriteHeader(Stream* stream) {
   CompactDexFile::Header header;
   CompactDexFile::WriteMagic(&header.magic_[0]);
   CompactDexFile::WriteCurrentVersion(&header.magic_[0]);
   header.checksum_ = header_->Checksum();
   std::copy_n(header_->Signature(), DexFile::kSha1DigestSize, header.signature_);
   header.file_size_ = header_->FileSize();
   // Since we are not necessarily outputting the same format as the input, avoid using the stored
   // header size.
   header.header_size_ = GetHeaderSize();
   header.endian_tag_ = header_->EndianTag();
   header.link_size_ = header_->LinkSize();
   header.link_off_ = header_->LinkOffset();
   header.map_off_ = header_->MapListOffset();
   header.string_ids_size_ = header_->StringIds().Size();
   header.string_ids_off_ = header_->StringIds().GetOffset();
   header.type_ids_size_ = header_->TypeIds().Size();
   header.type_ids_off_ = header_->TypeIds().GetOffset();
   header.proto_ids_size_ = header_->ProtoIds().Size();
   header.proto_ids_off_ = header_->ProtoIds().GetOffset();
   header.field_ids_size_ = header_->FieldIds().Size();
   header.field_ids_off_ = header_->FieldIds().GetOffset();
   header.method_ids_size_ = header_->MethodIds().Size();
   header.method_ids_off_ = header_->MethodIds().GetOffset();
   header.class_defs_size_ = header_->ClassDefs().Size();
   header.class_defs_off_ = header_->ClassDefs().GetOffset();
   header.data_size_ = header_->DataSize();
   header.data_off_ = header_->DataOffset();
   header.owned_data_begin_ = owned_data_begin_;
   header.owned_data_end_ = owned_data_end_;

   // Compact dex specific flags.
   header.debug_info_offsets_pos_ = debug_info_offsets_pos_;
   header.debug_info_offsets_table_offset_ = debug_info_offsets_table_offset_;
   header.debug_info_base_ = debug_info_base_;
   header.feature_flags_ = 0u;
   // In cases where apps are converted to cdex during install, maintain feature flags so that
   // the verifier correctly verifies apps that aren't targetting default methods.
   if (header_->SupportDefaultMethods()) {
     header.feature_flags_ |= static_cast<uint32_t>(CompactDexFile::FeatureFlags::kDefaultMethods);
   }
   stream->Seek(0);
   stream->Overwrite(reinterpret_cast<uint8_t*>(&header), sizeof(header));
 }

 size_t CompactDexWriter::GetHeaderSize() const {
   return sizeof(CompactDexFile::Header);
 }

 void CompactDexWriter::WriteStringData(Stream* stream, dex_ir::StringData* string_data) {
   ScopedDataSectionItem data_item(stream,
                                   string_data,
                                   SectionAlignment(DexFile::kDexTypeStringDataItem),
                                   data_item_dedupe_);
   ProcessOffset(stream, string_data);
   stream->WriteUleb128(CountModifiedUtf8Chars(string_data->Data()));
   stream->Write(string_data->Data(), strlen(string_data->Data()));
   // Skip null terminator (already zeroed out, no need to write).
   stream->Skip(1);
 }

 bool CompactDexWriter::CanGenerateCompactDex(std::string* error_msg) {
   static constexpr InvokeType invoke_types[] = {
     kDirect,
     kVirtual
   };
   std::vector<bool> saw_method_id(header_->MethodIds().Size(), false);
   std::vector<dex_ir::CodeItem*> method_id_code_item(header_->MethodIds().Size(), nullptr);
   std::vector<dex_ir::DebugInfoItem*> method_id_debug_info(header_->MethodIds().Size(), nullptr);
   for (InvokeType invoke_type : invoke_types) {
     for (auto& class_def : header_->ClassDefs()) {
       // Skip classes that are not defined in this dex file.
       dex_ir::ClassData* class_data = class_def->GetClassData();
       if (class_data == nullptr) {
         continue;
       }
       for (auto& method : *(invoke_type == InvokeType::kDirect
                                 ? class_data->DirectMethods()
                                 : class_data->VirtualMethods())) {
         const uint32_t idx = method.GetMethodId()->GetIndex();
         dex_ir::CodeItem* code_item = method.GetCodeItem();
         dex_ir:: DebugInfoItem* debug_info_item = nullptr;
         if (code_item != nullptr) {
           debug_info_item = code_item->DebugInfo();
         }
         if (saw_method_id[idx]) {
           if (method_id_code_item[idx] != code_item) {
             *error_msg = android::base::StringPrintf("Conflicting code item for method id %u",
                                                      idx);
             // Conflicting info, abort generation.
             return false;
           }
           if (method_id_debug_info[idx] != debug_info_item) {
             *error_msg = android::base::StringPrintf("Conflicting debug info for method id %u",
                                                      idx);
             // Conflicting info, abort generation.
             return false;
           }
         }
         method_id_code_item[idx] = code_item;
         method_id_debug_info[idx] = debug_info_item;
         saw_method_id[idx] = true;
       }
     }
   }
   return true;
 }

 bool CompactDexWriter::Write(DexContainer* output, std::string* error_msg)  {
   DCHECK(error_msg != nullptr);
   CHECK(compute_offsets_);
   CHECK(output->IsCompactDexContainer());

   if (!CanGenerateCompactDex(error_msg)) {
     return false;
   }

   Container* const container = down_cast<Container*>(output);
   // For now, use the same stream for both data and metadata.
   Stream temp_main_stream(output->GetMainSection());
   CHECK_EQ(output->GetMainSection()->Size(), 0u);
   Stream temp_data_stream(output->GetDataSection());
   Stream* main_stream = &temp_main_stream;
   Stream* data_stream = &temp_data_stream;

   // We want offset 0 to be reserved for null, seek to the data section alignment or the end of the
   // section.
   data_stream->Seek(std::max(
       static_cast<uint32_t>(output->GetDataSection()->Size()),
       kDataSectionAlignment));
   code_item_dedupe_ = &container->code_item_dedupe_;
   data_item_dedupe_ = &container->data_item_dedupe_;

   // Starting offset is right after the header.
   main_stream->Seek(GetHeaderSize());

   // Based on: https://source.android.com/devices/tech/dalvik/dex-format
   // Since the offsets may not be calculated already, the writing must be done in the correct order.
   const uint32_t string_ids_offset = main_stream->Tell();
   WriteStringIds(main_stream, /*reserve_only=*/ true);
   WriteTypeIds(main_stream);
   const uint32_t proto_ids_offset = main_stream->Tell();
   WriteProtoIds(main_stream, /*reserve_only=*/ true);
   WriteFieldIds(main_stream);
   WriteMethodIds(main_stream);
   const uint32_t class_defs_offset = main_stream->Tell();
   WriteClassDefs(main_stream, /*reserve_only=*/ true);
   const uint32_t call_site_ids_offset = main_stream->Tell();
   WriteCallSiteIds(main_stream, /*reserve_only=*/ true);
   WriteMethodHandles(main_stream);

   if (compute_offsets_) {
     // Data section.
     data_stream->AlignTo(kDataSectionAlignment);
   }
   owned_data_begin_ = data_stream->Tell();

   // Write code item first to minimize the space required for encoded methods.
   // For cdex, the code items don't depend on the debug info.
   WriteCodeItems(data_stream, /*reserve_only=*/ false);

   // Sort the debug infos by method index order, this reduces size by ~0.1% by reducing the size of
   // the debug info offset table.
   SortDebugInfosByMethodIndex();
   WriteDebugInfoItems(data_stream);

   WriteEncodedArrays(data_stream);
   WriteAnnotations(data_stream);
   WriteAnnotationSets(data_stream);
   WriteAnnotationSetRefs(data_stream);
   WriteAnnotationsDirectories(data_stream);
   WriteTypeLists(data_stream);
   WriteClassDatas(data_stream);
   WriteStringDatas(data_stream);
   WriteHiddenapiClassData(data_stream);

   // Write delayed id sections that depend on data sections.
   {
     Stream::ScopedSeek seek(main_stream, string_ids_offset);
     WriteStringIds(main_stream, /*reserve_only=*/ false);
   }
   {
     Stream::ScopedSeek seek(main_stream, proto_ids_offset);
     WriteProtoIds(main_stream, /*reserve_only=*/ false);
   }
   {
     Stream::ScopedSeek seek(main_stream, class_defs_offset);
     WriteClassDefs(main_stream, /*reserve_only=*/ false);
   }
   {
     Stream::ScopedSeek seek(main_stream, call_site_ids_offset);
     WriteCallSiteIds(main_stream, /*reserve_only=*/ false);
   }

   // Write the map list.
   if (compute_offsets_) {
     data_stream->AlignTo(SectionAlignment(DexFile::kDexTypeMapList));
     header_->SetMapListOffset(data_stream->Tell());
   } else {
     data_stream->Seek(header_->MapListOffset());
   }

   // Map items are included in the data section.
   GenerateAndWriteMapItems(data_stream);

   // Write link data if it exists.
   const std::vector<uint8_t>& link_data = header_->LinkData();
   if (link_data.size() > 0) {
     CHECK_EQ(header_->LinkSize(), static_cast<uint32_t>(link_data.size()));
     if (compute_offsets_) {
       header_->SetLinkOffset(data_stream->Tell());
     } else {
       data_stream->Seek(header_->LinkOffset());
     }
     data_stream->Write(&link_data[0], link_data.size());
   }

   // Write debug info offset table last to make dex file verifier happy.
   WriteDebugInfoOffsetTable(data_stream);

   data_stream->AlignTo(kDataSectionAlignment);
   owned_data_end_ = data_stream->Tell();
   if (compute_offsets_) {
     header_->SetDataSize(data_stream->Tell());
     if (header_->DataSize() != 0) {
       // Offset must be zero when the size is zero.
       main_stream->AlignTo(kDataSectionAlignment);
       // For now, default to saying the data is right after the main stream.
       header_->SetDataOffset(main_stream->Tell());
     } else {
       header_->SetDataOffset(0u);
     }
   }

   // Write header last.
   if (compute_offsets_) {
     header_->SetFileSize(main_stream->Tell());
   }
   WriteHeader(main_stream);

   // Trim sections to make sure they are sized properly.
   output->GetMainSection()->Resize(header_->FileSize());
   output->GetDataSection()->Resize(data_stream->Tell());

   if (dex_layout_->GetOptions().update_checksum_) {
     // Compute the cdex section (also covers the used part of the data section).
     header_->SetChecksum(CompactDexFile::CalculateChecksum(output->GetMainSection()->Begin(),
                                                            output->GetMainSection()->Size(),
                                                            output->GetDataSection()->Begin(),
                                                            output->GetDataSection()->Size()));
     // Rewrite the header with the calculated checksum.
     WriteHeader(main_stream);
   }

   // Clear the dedupe to prevent interdex code item deduping. This does not currently work well with
   // dex2oat's class unloading. The issue is that verification encounters quickened opcodes after
   // the first dex gets unloaded.
   code_item_dedupe_->Clear();

   return true;
 }

 std::unique_ptr<DexContainer> CompactDexWriter::CreateDexContainer() const {
   return std::unique_ptr<DexContainer>(
       new CompactDexWriter::Container(dex_layout_->GetOptions().dedupe_code_items_));
 }

 }  // namespace art
	/*
	* 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.
	*/

	#include "compact_dex_writer.h"

	#include "android-base/stringprintf.h"
	#include "base/logging.h"
	#include "base/time_utils.h"
	#include "dex/compact_dex_file.h"
	#include "dex/compact_offset_table.h"
	#include "dexlayout.h"

	namespace art {

	CompactDexWriter::CompactDexWriter(DexLayout* dex_layout)
	: DexWriter(dex_layout, /compute_offsets=/ true) {
	CHECK(GetCompactDexLevel() != CompactDexLevel::kCompactDexLevelNone);
	}

	CompactDexLevel CompactDexWriter::GetCompactDexLevel() const {
	return dex_layout_->GetOptions().compact_dex_level_;
	}

	CompactDexWriter::Container::Container(bool dedupe_code_items)
	: code_item_dedupe_(dedupe_code_items, &data_section_),
	data_item_dedupe_(/enabled=/ true, &data_section_) {}

	uint32_t CompactDexWriter::WriteDebugInfoOffsetTable(Stream* stream) {
	const uint32_t start_offset = stream->Tell();
	// Debug offsets for method indexes. 0 means no debug info.
	std::vector<uint32_t> debug_info_offsets(header_->MethodIds().Size(), 0u);

	static constexpr InvokeType invoke_types[] = {
	kDirect,
	kVirtual
	};

	for (InvokeType invoke_type : invoke_types) {
	for (auto& class_def : header_->ClassDefs()) {
	// Skip classes that are not defined in this dex file.
	dex_ir::ClassData* class_data = class_def->GetClassData();
	if (class_data == nullptr) {
	continue;
	}
	for (auto& method : *(invoke_type == InvokeType::kDirect
	? class_data->DirectMethods()
	: class_data->VirtualMethods())) {
	const dex_ir::MethodId* method_id = method.GetMethodId();
	dex_ir::CodeItem* code_item = method.GetCodeItem();
	if (code_item != nullptr && code_item->DebugInfo() != nullptr) {
	const uint32_t debug_info_offset = code_item->DebugInfo()->GetOffset();
	const uint32_t method_idx = method_id->GetIndex();
	if (debug_info_offsets[method_idx] != 0u) {
	CHECK_EQ(debug_info_offset, debug_info_offsets[method_idx]);
	}
	debug_info_offsets[method_idx] = debug_info_offset;
	}
	}
	}
	}

	std::vector<uint8_t> data;
	debug_info_base_ = 0u;
	debug_info_offsets_table_offset_ = 0u;
	CompactOffsetTable::Build(debug_info_offsets,
	&data,
	&debug_info_base_,
	&debug_info_offsets_table_offset_);
	// Align the table and write it out.
	stream->AlignTo(CompactOffsetTable::kAlignment);
	debug_info_offsets_pos_ = stream->Tell();
	stream->Write(data.data(), data.size());

	// Verify that the whole table decodes as expected and measure average performance.
	const bool kMeasureAndTestOutput = dex_layout_->GetOptions().verify_output_;
	if (kMeasureAndTestOutput && !debug_info_offsets.empty()) {
	uint64_t start_time = NanoTime();
	stream->Begin();
	CompactOffsetTable::Accessor accessor(stream->Begin() + debug_info_offsets_pos_,
	debug_info_base_,
	debug_info_offsets_table_offset_);

	for (size_t i = 0; i < debug_info_offsets.size(); ++i) {
	CHECK_EQ(accessor.GetOffset(i), debug_info_offsets[i]);
	}
	uint64_t end_time = NanoTime();
	VLOG(dex) << "Average lookup time (ns) for debug info offsets: "
	<< (end_time - start_time) / debug_info_offsets.size();
	}

	return stream->Tell() - start_offset;
	}

	CompactDexWriter::ScopedDataSectionItem::ScopedDataSectionItem(Stream* stream,
	dex_ir::Item* item,
	size_t alignment,
	Deduper* deduper)
	: stream_(stream),
	item_(item),
	alignment_(alignment),
	deduper_(deduper),
	start_offset_(stream->Tell()) {
	stream_->AlignTo(alignment_);
	}

	CompactDexWriter::ScopedDataSectionItem::~ScopedDataSectionItem() {
	// After having written, maybe dedupe the whole code item (excluding padding).
	const uint32_t deduped_offset = deduper_->Dedupe(start_offset_,
	stream_->Tell(),
	item_->GetOffset());
	// If we deduped, only use the deduped offset if the alignment matches the required alignment.
	// Otherwise, return without deduping.
	if (deduped_offset != Deduper::kDidNotDedupe && IsAlignedParam(deduped_offset, alignment_)) {
	// Update the IR offset to the offset of the deduped item.
	item_->SetOffset(deduped_offset);
	// Clear the written data for the item so that the stream write doesn't abort in the future.
	stream_->Clear(start_offset_, stream_->Tell() - start_offset_);
	// Since we deduped, restore the offset to the original position.
	stream_->Seek(start_offset_);
	}
	}

	size_t CompactDexWriter::ScopedDataSectionItem::Written() const {
	return stream_->Tell() - start_offset_;
	}

	void CompactDexWriter::WriteCodeItem(Stream* stream,
	dex_ir::CodeItem* code_item,
	bool reserve_only) {
	DCHECK(code_item != nullptr);
	DCHECK(!reserve_only) << "Not supported because of deduping.";
	ScopedDataSectionItem data_item(stream,
	code_item,
	CompactDexFile::CodeItem::kAlignment,
	code_item_dedupe_);

	CompactDexFile::CodeItem disk_code_item;

	uint16_t preheader_storage[CompactDexFile::CodeItem::kMaxPreHeaderSize] = {};
	uint16_t* preheader_end = preheader_storage + CompactDexFile::CodeItem::kMaxPreHeaderSize;
	const uint16_t* preheader = disk_code_item.Create(
	code_item->RegistersSize(),
	code_item->InsSize(),
	code_item->OutsSize(),
	code_item->TriesSize(),
	code_item->InsnsSize(),
	preheader_end);
	const size_t preheader_bytes = (preheader_end - preheader) * sizeof(preheader[0]);

	static constexpr size_t kPayloadInstructionRequiredAlignment = 4;
	const uint32_t current_code_item_start = stream->Tell() + preheader_bytes;
	if (!IsAlignedParam(current_code_item_start, kPayloadInstructionRequiredAlignment) \|\|
	kIsDebugBuild) {
	// If the preheader is going to make the code unaligned, consider adding 2 bytes of padding
	// before if required.
	IterationRange<DexInstructionIterator> instructions = code_item->Instructions();
	SafeDexInstructionIterator it(instructions.begin(), instructions.end());
	for (; !it.IsErrorState() && it < instructions.end(); ++it) {
	// In case the instruction goes past the end of the code item, make sure to not process it.
	if (std::next(it).IsErrorState()) {
	break;
	}
	const Instruction::Code opcode = it->Opcode();
	// Payload instructions possibly require special alignment for their data.
	if (opcode == Instruction::FILL_ARRAY_DATA \|\|
	opcode == Instruction::PACKED_SWITCH \|\|
	opcode == Instruction::SPARSE_SWITCH) {
	stream->Skip(
	RoundUp(current_code_item_start, kPayloadInstructionRequiredAlignment) -
	current_code_item_start);
	break;
	}
	}
	}

	// Write preheader first.
	stream->Write(reinterpret_cast<const uint8_t*>(preheader), preheader_bytes);
	// Registered offset is after the preheader.
	ProcessOffset(stream, code_item);
	// Avoid using sizeof so that we don't write the fake instruction array at the end of the code
	// item.
	stream->Write(&disk_code_item, OFFSETOF_MEMBER(CompactDexFile::CodeItem, insns_));
	// Write the instructions.
	stream->Write(code_item->Insns(), code_item->InsnsSize() * sizeof(uint16_t));
	// Write the post instruction data.
	WriteCodeItemPostInstructionData(stream, code_item, reserve_only);
	}

	void CompactDexWriter::WriteDebugInfoItem(Stream* stream, dex_ir::DebugInfoItem* debug_info) {
	ScopedDataSectionItem data_item(stream,
	debug_info,
	SectionAlignment(DexFile::kDexTypeDebugInfoItem),
	data_item_dedupe_);
	ProcessOffset(stream, debug_info);
	stream->Write(debug_info->GetDebugInfo(), debug_info->GetDebugInfoSize());
	}


	CompactDexWriter::Deduper::Deduper(bool enabled, DexContainer::Section* section)
	: enabled_(enabled),
	dedupe_map_(/__n=/ 32,
	HashedMemoryRange::HashEqual(section),
	HashedMemoryRange::HashEqual(section)) {}

	uint32_t CompactDexWriter::Deduper::Dedupe(uint32_t data_start,
	uint32_t data_end,
	uint32_t item_offset) {
	if (!enabled_) {
	return kDidNotDedupe;
	}
	HashedMemoryRange range {data_start, data_end - data_start};
	auto existing = dedupe_map_.emplace(range, item_offset);
	if (!existing.second) {
	// Failed to insert means we deduped, return the existing item offset.
	return existing.first->second;
	}
	return kDidNotDedupe;
	}

	void CompactDexWriter::SortDebugInfosByMethodIndex() {
	static constexpr InvokeType invoke_types[] = {
	kDirect,
	kVirtual
	};
	std::map<const dex_ir::DebugInfoItem*, uint32_t> method_idx_map;
	for (InvokeType invoke_type : invoke_types) {
	for (auto& class_def : header_->ClassDefs()) {
	// Skip classes that are not defined in this dex file.
	dex_ir::ClassData* class_data = class_def->GetClassData();
	if (class_data == nullptr) {
	continue;
	}
	for (auto& method : *(invoke_type == InvokeType::kDirect
	? class_data->DirectMethods()
	: class_data->VirtualMethods())) {
	const dex_ir::MethodId* method_id = method.GetMethodId();
	dex_ir::CodeItem* code_item = method.GetCodeItem();
	if (code_item != nullptr && code_item->DebugInfo() != nullptr) {
	const dex_ir::DebugInfoItem* debug_item = code_item->DebugInfo();
	method_idx_map.insert(std::make_pair(debug_item, method_id->GetIndex()));
	}
	}
	}
	}
	std::sort(header_->DebugInfoItems().begin(),
	header_->DebugInfoItems().end(),
	[&](const std::unique_ptr<dex_ir::DebugInfoItem>& a,
	const std::unique_ptr<dex_ir::DebugInfoItem>& b) {
	auto it_a = method_idx_map.find(a.get());
	auto it_b = method_idx_map.find(b.get());
	uint32_t idx_a = it_a != method_idx_map.end() ? it_a->second : 0u;
	uint32_t idx_b = it_b != method_idx_map.end() ? it_b->second : 0u;
	return idx_a < idx_b;
	});
	}

	void CompactDexWriter::WriteHeader(Stream* stream) {
	CompactDexFile::Header header;
	CompactDexFile::WriteMagic(&header.magic_[0]);
	CompactDexFile::WriteCurrentVersion(&header.magic_[0]);
	header.checksum_ = header_->Checksum();
	std::copy_n(header_->Signature(), DexFile::kSha1DigestSize, header.signature_);
	header.file_size_ = header_->FileSize();
	// Since we are not necessarily outputting the same format as the input, avoid using the stored
	// header size.
	header.header_size_ = GetHeaderSize();
	header.endian_tag_ = header_->EndianTag();
	header.link_size_ = header_->LinkSize();
	header.link_off_ = header_->LinkOffset();
	header.map_off_ = header_->MapListOffset();
	header.string_ids_size_ = header_->StringIds().Size();
	header.string_ids_off_ = header_->StringIds().GetOffset();
	header.type_ids_size_ = header_->TypeIds().Size();
	header.type_ids_off_ = header_->TypeIds().GetOffset();
	header.proto_ids_size_ = header_->ProtoIds().Size();
	header.proto_ids_off_ = header_->ProtoIds().GetOffset();
	header.field_ids_size_ = header_->FieldIds().Size();
	header.field_ids_off_ = header_->FieldIds().GetOffset();
	header.method_ids_size_ = header_->MethodIds().Size();
	header.method_ids_off_ = header_->MethodIds().GetOffset();
	header.class_defs_size_ = header_->ClassDefs().Size();
	header.class_defs_off_ = header_->ClassDefs().GetOffset();
	header.data_size_ = header_->DataSize();
	header.data_off_ = header_->DataOffset();
	header.owned_data_begin_ = owned_data_begin_;
	header.owned_data_end_ = owned_data_end_;

	// Compact dex specific flags.
	header.debug_info_offsets_pos_ = debug_info_offsets_pos_;
	header.debug_info_offsets_table_offset_ = debug_info_offsets_table_offset_;
	header.debug_info_base_ = debug_info_base_;
	header.feature_flags_ = 0u;
	// In cases where apps are converted to cdex during install, maintain feature flags so that
	// the verifier correctly verifies apps that aren't targetting default methods.
	if (header_->SupportDefaultMethods()) {
	header.feature_flags_ \|= static_cast<uint32_t>(CompactDexFile::FeatureFlags::kDefaultMethods);
	}
	stream->Seek(0);
	stream->Overwrite(reinterpret_cast<uint8_t*>(&header), sizeof(header));
	}

	size_t CompactDexWriter::GetHeaderSize() const {
	return sizeof(CompactDexFile::Header);
	}

	void CompactDexWriter::WriteStringData(Stream* stream, dex_ir::StringData* string_data) {
	ScopedDataSectionItem data_item(stream,
	string_data,
	SectionAlignment(DexFile::kDexTypeStringDataItem),
	data_item_dedupe_);
	ProcessOffset(stream, string_data);
	stream->WriteUleb128(CountModifiedUtf8Chars(string_data->Data()));
	stream->Write(string_data->Data(), strlen(string_data->Data()));
	// Skip null terminator (already zeroed out, no need to write).
	stream->Skip(1);
	}

	bool CompactDexWriter::CanGenerateCompactDex(std::string* error_msg) {
	static constexpr InvokeType invoke_types[] = {
	kDirect,
	kVirtual
	};
	std::vector<bool> saw_method_id(header_->MethodIds().Size(), false);
	std::vector<dex_ir::CodeItem*> method_id_code_item(header_->MethodIds().Size(), nullptr);
	std::vector<dex_ir::DebugInfoItem*> method_id_debug_info(header_->MethodIds().Size(), nullptr);
	for (InvokeType invoke_type : invoke_types) {
	for (auto& class_def : header_->ClassDefs()) {
	// Skip classes that are not defined in this dex file.
	dex_ir::ClassData* class_data = class_def->GetClassData();
	if (class_data == nullptr) {
	continue;
	}
	for (auto& method : *(invoke_type == InvokeType::kDirect
	? class_data->DirectMethods()
	: class_data->VirtualMethods())) {
	const uint32_t idx = method.GetMethodId()->GetIndex();
	dex_ir::CodeItem* code_item = method.GetCodeItem();
	dex_ir:: DebugInfoItem* debug_info_item = nullptr;
	if (code_item != nullptr) {
	debug_info_item = code_item->DebugInfo();
	}
	if (saw_method_id[idx]) {
	if (method_id_code_item[idx] != code_item) {
	*error_msg = android::base::StringPrintf("Conflicting code item for method id %u",
	idx);
	// Conflicting info, abort generation.
	return false;
	}
	if (method_id_debug_info[idx] != debug_info_item) {
	*error_msg = android::base::StringPrintf("Conflicting debug info for method id %u",
	idx);
	// Conflicting info, abort generation.
	return false;
	}
	}
	method_id_code_item[idx] = code_item;
	method_id_debug_info[idx] = debug_info_item;
	saw_method_id[idx] = true;
	}
	}
	}
	return true;
	}

	bool CompactDexWriter::Write(DexContainer* output, std::string* error_msg) {
	DCHECK(error_msg != nullptr);
	CHECK(compute_offsets_);
	CHECK(output->IsCompactDexContainer());

	if (!CanGenerateCompactDex(error_msg)) {
	return false;
	}

	Container* const container = down_cast<Container*>(output);
	// For now, use the same stream for both data and metadata.
	Stream temp_main_stream(output->GetMainSection());
	CHECK_EQ(output->GetMainSection()->Size(), 0u);
	Stream temp_data_stream(output->GetDataSection());
	Stream* main_stream = &temp_main_stream;
	Stream* data_stream = &temp_data_stream;

	// We want offset 0 to be reserved for null, seek to the data section alignment or the end of the
	// section.
	data_stream->Seek(std::max(
	static_cast<uint32_t>(output->GetDataSection()->Size()),
	kDataSectionAlignment));
	code_item_dedupe_ = &container->code_item_dedupe_;
	data_item_dedupe_ = &container->data_item_dedupe_;

	// Starting offset is right after the header.
	main_stream->Seek(GetHeaderSize());

	// Based on: https://source.android.com/devices/tech/dalvik/dex-format
	// Since the offsets may not be calculated already, the writing must be done in the correct order.
	const uint32_t string_ids_offset = main_stream->Tell();
	WriteStringIds(main_stream, /reserve_only=/ true);
	WriteTypeIds(main_stream);
	const uint32_t proto_ids_offset = main_stream->Tell();
	WriteProtoIds(main_stream, /reserve_only=/ true);
	WriteFieldIds(main_stream);
	WriteMethodIds(main_stream);
	const uint32_t class_defs_offset = main_stream->Tell();
	WriteClassDefs(main_stream, /reserve_only=/ true);
	const uint32_t call_site_ids_offset = main_stream->Tell();
	WriteCallSiteIds(main_stream, /reserve_only=/ true);
	WriteMethodHandles(main_stream);

	if (compute_offsets_) {
	// Data section.
	data_stream->AlignTo(kDataSectionAlignment);
	}
	owned_data_begin_ = data_stream->Tell();

	// Write code item first to minimize the space required for encoded methods.
	// For cdex, the code items don't depend on the debug info.
	WriteCodeItems(data_stream, /reserve_only=/ false);

	// Sort the debug infos by method index order, this reduces size by ~0.1% by reducing the size of
	// the debug info offset table.
	SortDebugInfosByMethodIndex();
	WriteDebugInfoItems(data_stream);

	WriteEncodedArrays(data_stream);
	WriteAnnotations(data_stream);
	WriteAnnotationSets(data_stream);
	WriteAnnotationSetRefs(data_stream);
	WriteAnnotationsDirectories(data_stream);
	WriteTypeLists(data_stream);
	WriteClassDatas(data_stream);
	WriteStringDatas(data_stream);
	WriteHiddenapiClassData(data_stream);

	// Write delayed id sections that depend on data sections.
	{
	Stream::ScopedSeek seek(main_stream, string_ids_offset);
	WriteStringIds(main_stream, /reserve_only=/ false);
	}
	{
	Stream::ScopedSeek seek(main_stream, proto_ids_offset);
	WriteProtoIds(main_stream, /reserve_only=/ false);
	}
	{
	Stream::ScopedSeek seek(main_stream, class_defs_offset);
	WriteClassDefs(main_stream, /reserve_only=/ false);
	}
	{
	Stream::ScopedSeek seek(main_stream, call_site_ids_offset);
	WriteCallSiteIds(main_stream, /reserve_only=/ false);
	}

	// Write the map list.
	if (compute_offsets_) {
	data_stream->AlignTo(SectionAlignment(DexFile::kDexTypeMapList));
	header_->SetMapListOffset(data_stream->Tell());
	} else {
	data_stream->Seek(header_->MapListOffset());
	}

	// Map items are included in the data section.
	GenerateAndWriteMapItems(data_stream);

	// Write link data if it exists.
	const std::vector<uint8_t>& link_data = header_->LinkData();
	if (link_data.size() > 0) {
	CHECK_EQ(header_->LinkSize(), static_cast<uint32_t>(link_data.size()));
	if (compute_offsets_) {
	header_->SetLinkOffset(data_stream->Tell());
	} else {
	data_stream->Seek(header_->LinkOffset());
	}
	data_stream->Write(&link_data[0], link_data.size());
	}

	// Write debug info offset table last to make dex file verifier happy.
	WriteDebugInfoOffsetTable(data_stream);

	data_stream->AlignTo(kDataSectionAlignment);
	owned_data_end_ = data_stream->Tell();
	if (compute_offsets_) {
	header_->SetDataSize(data_stream->Tell());
	if (header_->DataSize() != 0) {
	// Offset must be zero when the size is zero.
	main_stream->AlignTo(kDataSectionAlignment);
	// For now, default to saying the data is right after the main stream.
	header_->SetDataOffset(main_stream->Tell());
	} else {
	header_->SetDataOffset(0u);
	}
	}

	// Write header last.
	if (compute_offsets_) {
	header_->SetFileSize(main_stream->Tell());
	}
	WriteHeader(main_stream);

	// Trim sections to make sure they are sized properly.
	output->GetMainSection()->Resize(header_->FileSize());
	output->GetDataSection()->Resize(data_stream->Tell());

	if (dex_layout_->GetOptions().update_checksum_) {
	// Compute the cdex section (also covers the used part of the data section).
	header_->SetChecksum(CompactDexFile::CalculateChecksum(output->GetMainSection()->Begin(),
	output->GetMainSection()->Size(),
	output->GetDataSection()->Begin(),
	output->GetDataSection()->Size()));
	// Rewrite the header with the calculated checksum.
	WriteHeader(main_stream);
	}

	// Clear the dedupe to prevent interdex code item deduping. This does not currently work well with
	// dex2oat's class unloading. The issue is that verification encounters quickened opcodes after
	// the first dex gets unloaded.
	code_item_dedupe_->Clear();

	return true;
	}

	std::unique_ptr<DexContainer> CompactDexWriter::CreateDexContainer() const {
	return std::unique_ptr<DexContainer>(
	new CompactDexWriter::Container(dex_layout_->GetOptions().dedupe_code_items_));
	}

	} // namespace art