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
30namespace art {
31namespace 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.
39template <typename Vector = std::vector<uint8_t>>
40class 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