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      1 /*
      2  * Copyright (C) 2016 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #ifndef ART_COMPILER_DEBUG_DWARF_DEBUG_ABBREV_WRITER_H_
     18 #define ART_COMPILER_DEBUG_DWARF_DEBUG_ABBREV_WRITER_H_
     19 
     20 #include <cstdint>
     21 #include <type_traits>
     22 #include <unordered_map>
     23 
     24 #include "base/casts.h"
     25 #include "base/stl_util.h"
     26 #include "debug/dwarf/dwarf_constants.h"
     27 #include "debug/dwarf/writer.h"
     28 #include "leb128.h"
     29 
     30 namespace art {
     31 namespace dwarf {
     32 
     33 // Writer for the .debug_abbrev.
     34 //
     35 // Abbreviations specify the format of entries in .debug_info.
     36 // Each entry specifies abbreviation code, which in turns
     37 // determines all the attributes and their format.
     38 // It is possible to think of them as type definitions.
     39 template <typename Vector = std::vector<uint8_t>>
     40 class DebugAbbrevWriter FINAL : private Writer<Vector> {
     41   static_assert(std::is_same<typename Vector::value_type, uint8_t>::value, "Invalid value type");
     42 
     43  public:
     44   explicit DebugAbbrevWriter(Vector* buffer)
     45       : Writer<Vector>(buffer),
     46         current_abbrev_(buffer->get_allocator()) {
     47     this->PushUint8(0);  // Add abbrev table terminator.
     48   }
     49 
     50   // Start abbreviation declaration.
     51   void StartAbbrev(Tag tag) {
     52     DCHECK(current_abbrev_.empty());
     53     EncodeUnsignedLeb128(&current_abbrev_, tag);
     54     has_children_offset_ = current_abbrev_.size();
     55     current_abbrev_.push_back(0);  // Place-holder for DW_CHILDREN.
     56   }
     57 
     58   // Add attribute specification.
     59   void AddAbbrevAttribute(Attribute name, Form type) {
     60     EncodeUnsignedLeb128(&current_abbrev_, name);
     61     EncodeUnsignedLeb128(&current_abbrev_, type);
     62   }
     63 
     64   // End abbreviation declaration and return its code.
     65   // This will deduplicate abbreviations.
     66   uint32_t EndAbbrev(Children has_children) {
     67     DCHECK(!current_abbrev_.empty());
     68     current_abbrev_[has_children_offset_] = has_children;
     69     auto it = abbrev_codes_.insert(std::make_pair(std::move(current_abbrev_), NextAbbrevCode()));
     70     uint32_t abbrev_code = it.first->second;
     71     if (UNLIKELY(it.second)) {  // Inserted new entry.
     72       const Vector& abbrev = it.first->first;
     73       this->Pop();  // Remove abbrev table terminator.
     74       this->PushUleb128(abbrev_code);
     75       this->PushData(abbrev.data(), abbrev.size());
     76       this->PushUint8(0);  // Attribute list end.
     77       this->PushUint8(0);  // Attribute list end.
     78       this->PushUint8(0);  // Add abbrev table terminator.
     79     }
     80     current_abbrev_.clear();
     81     return abbrev_code;
     82   }
     83 
     84   // Get the next free abbrev code.
     85   uint32_t NextAbbrevCode() {
     86     return dchecked_integral_cast<uint32_t>(1 + abbrev_codes_.size());
     87   }
     88 
     89  private:
     90   Vector current_abbrev_;
     91   size_t has_children_offset_ = 0;
     92   std::unordered_map<Vector, uint32_t, FNVHash<Vector> > abbrev_codes_;
     93 };
     94 
     95 }  // namespace dwarf
     96 }  // namespace art
     97 
     98 #endif  // ART_COMPILER_DEBUG_DWARF_DEBUG_ABBREV_WRITER_H_
     99