/*
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* Copyright (C) 2015 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef ART_LIBELFFILE_DWARF_DEBUG_LINE_OPCODE_WRITER_H_
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#define ART_LIBELFFILE_DWARF_DEBUG_LINE_OPCODE_WRITER_H_
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#include <cstdint>
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#include "dwarf/dwarf_constants.h"
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#include "dwarf/writer.h"
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namespace art {
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namespace dwarf {
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// Writer for the .debug_line opcodes (DWARF-3).
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// The writer is very light-weight, however it will do the following for you:
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// * Choose the most compact encoding of a given opcode.
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// * Keep track of current state and convert absolute values to deltas.
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// * Divide by header-defined factors as appropriate.
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template<typename Vector = std::vector<uint8_t>>
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class DebugLineOpCodeWriter final : private Writer<Vector> {
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static_assert(std::is_same<typename Vector::value_type, uint8_t>::value, "Invalid value type");
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public:
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static constexpr int kOpcodeBase = 13;
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static constexpr bool kDefaultIsStmt = false;
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static constexpr int kLineBase = -5;
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static constexpr int kLineRange = 14;
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void AddRow() {
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this->PushUint8(DW_LNS_copy);
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}
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void AdvancePC(uint64_t absolute_address) {
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DCHECK_NE(current_address_, 0u); // Use SetAddress for the first advance.
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DCHECK_GE(absolute_address, current_address_);
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if (absolute_address != current_address_) {
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uint64_t delta = FactorCodeOffset(absolute_address - current_address_);
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if (delta <= INT32_MAX) {
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this->PushUint8(DW_LNS_advance_pc);
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this->PushUleb128(static_cast<int>(delta));
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current_address_ = absolute_address;
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} else {
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SetAddress(absolute_address);
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}
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}
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}
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void AdvanceLine(int absolute_line) {
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int delta = absolute_line - current_line_;
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if (delta != 0) {
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this->PushUint8(DW_LNS_advance_line);
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this->PushSleb128(delta);
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current_line_ = absolute_line;
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}
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}
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void SetFile(int file) {
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if (current_file_ != file) {
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this->PushUint8(DW_LNS_set_file);
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this->PushUleb128(file);
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current_file_ = file;
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}
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}
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void SetColumn(int column) {
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this->PushUint8(DW_LNS_set_column);
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this->PushUleb128(column);
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}
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void SetIsStmt(bool is_stmt) {
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if (is_stmt_ != is_stmt) {
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this->PushUint8(DW_LNS_negate_stmt);
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is_stmt_ = is_stmt;
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}
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}
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void SetBasicBlock() {
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this->PushUint8(DW_LNS_set_basic_block);
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}
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void SetPrologueEnd() {
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uses_dwarf3_features_ = true;
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this->PushUint8(DW_LNS_set_prologue_end);
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}
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void SetEpilogueBegin() {
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uses_dwarf3_features_ = true;
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this->PushUint8(DW_LNS_set_epilogue_begin);
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}
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void SetISA(int isa) {
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uses_dwarf3_features_ = true;
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this->PushUint8(DW_LNS_set_isa);
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this->PushUleb128(isa);
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}
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void EndSequence() {
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this->PushUint8(0);
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this->PushUleb128(1);
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this->PushUint8(DW_LNE_end_sequence);
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current_address_ = 0;
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current_file_ = 1;
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current_line_ = 1;
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is_stmt_ = kDefaultIsStmt;
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}
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// Uncoditionally set address using the long encoding.
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// This gives the linker opportunity to relocate the address.
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void SetAddress(uint64_t absolute_address) {
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DCHECK_GE(absolute_address, current_address_);
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FactorCodeOffset(absolute_address); // Check if it is factorable.
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this->PushUint8(0);
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if (use_64bit_address_) {
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this->PushUleb128(1 + 8);
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this->PushUint8(DW_LNE_set_address);
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patch_locations_.push_back(this->data()->size());
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this->PushUint64(absolute_address);
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} else {
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this->PushUleb128(1 + 4);
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this->PushUint8(DW_LNE_set_address);
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patch_locations_.push_back(this->data()->size());
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this->PushUint32(absolute_address);
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}
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current_address_ = absolute_address;
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}
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void DefineFile(const char* filename,
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int directory_index,
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int modification_time,
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int file_size) {
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int size = 1 +
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strlen(filename) + 1 +
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UnsignedLeb128Size(directory_index) +
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UnsignedLeb128Size(modification_time) +
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UnsignedLeb128Size(file_size);
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this->PushUint8(0);
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this->PushUleb128(size);
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size_t start = data()->size();
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this->PushUint8(DW_LNE_define_file);
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this->PushString(filename);
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this->PushUleb128(directory_index);
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this->PushUleb128(modification_time);
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this->PushUleb128(file_size);
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DCHECK_EQ(start + size, data()->size());
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}
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// Compact address and line opcode.
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void AddRow(uint64_t absolute_address, int absolute_line) {
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DCHECK_GE(absolute_address, current_address_);
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// If the address is definitely too far, use the long encoding.
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uint64_t delta_address = FactorCodeOffset(absolute_address - current_address_);
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if (delta_address > UINT8_MAX) {
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AdvancePC(absolute_address);
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delta_address = 0;
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}
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// If the line is definitely too far, use the long encoding.
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int delta_line = absolute_line - current_line_;
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if (!(kLineBase <= delta_line && delta_line < kLineBase + kLineRange)) {
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AdvanceLine(absolute_line);
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delta_line = 0;
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}
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// Both address and line should be reasonable now. Use the short encoding.
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int opcode = kOpcodeBase + (delta_line - kLineBase) +
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(static_cast<int>(delta_address) * kLineRange);
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if (opcode > UINT8_MAX) {
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// If the address is still too far, try to increment it by const amount.
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int const_advance = (0xFF - kOpcodeBase) / kLineRange;
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opcode -= (kLineRange * const_advance);
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if (opcode <= UINT8_MAX) {
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this->PushUint8(DW_LNS_const_add_pc);
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} else {
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// Give up and use long encoding for address.
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AdvancePC(absolute_address);
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// Still use the opcode to do line advance and copy.
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opcode = kOpcodeBase + (delta_line - kLineBase);
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}
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}
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DCHECK(kOpcodeBase <= opcode && opcode <= 0xFF);
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this->PushUint8(opcode); // Special opcode.
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current_line_ = absolute_line;
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current_address_ = absolute_address;
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}
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int GetCodeFactorBits() const {
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return code_factor_bits_;
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}
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uint64_t CurrentAddress() const {
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return current_address_;
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}
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int CurrentFile() const {
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return current_file_;
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}
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int CurrentLine() const {
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return current_line_;
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}
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const std::vector<uintptr_t>& GetPatchLocations() const {
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return patch_locations_;
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}
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using Writer<Vector>::data;
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DebugLineOpCodeWriter(bool use64bitAddress,
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int codeFactorBits,
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const typename Vector::allocator_type& alloc =
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typename Vector::allocator_type())
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: Writer<Vector>(&opcodes_),
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opcodes_(alloc),
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uses_dwarf3_features_(false),
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use_64bit_address_(use64bitAddress),
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code_factor_bits_(codeFactorBits),
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current_address_(0),
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current_file_(1),
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current_line_(1),
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is_stmt_(kDefaultIsStmt) {
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}
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private:
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uint64_t FactorCodeOffset(uint64_t offset) const {
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DCHECK_GE(code_factor_bits_, 0);
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DCHECK_EQ((offset >> code_factor_bits_) << code_factor_bits_, offset);
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return offset >> code_factor_bits_;
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}
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Vector opcodes_;
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bool uses_dwarf3_features_;
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bool use_64bit_address_;
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int code_factor_bits_;
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uint64_t current_address_;
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int current_file_;
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int current_line_;
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bool is_stmt_;
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std::vector<uintptr_t> patch_locations_;
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DISALLOW_COPY_AND_ASSIGN(DebugLineOpCodeWriter);
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};
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} // namespace dwarf
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} // namespace art
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#endif // ART_LIBELFFILE_DWARF_DEBUG_LINE_OPCODE_WRITER_H_
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