bool LineInfo::ProcessOneOpcode()

in src/common/dwarf/dwarf2reader.cc [1011:1195]
149 lines of code
29 McCabe index (conditional complexity)

bool LineInfo::ProcessOneOpcode(ByteReader* reader,
                                LineInfoHandler* handler,
                                const struct LineInfoHeader &header,
                                const uint8_t *start,
                                struct LineStateMachine* lsm,
                                size_t* len,
                                uintptr pc,
                                bool *lsm_passes_pc) {
  size_t oplen = 0;
  size_t templen;
  uint8 opcode = reader->ReadOneByte(start);
  oplen++;
  start++;

  // If the opcode is great than the opcode_base, it is a special
  // opcode. Most line programs consist mainly of special opcodes.
  if (opcode >= header.opcode_base) {
    opcode -= header.opcode_base;
    const int64 advance_address = (opcode / header.line_range)
                                  * header.min_insn_length;
    const int32 advance_line = (opcode % header.line_range)
                               + header.line_base;

    // Check if the lsm passes "pc". If so, mark it as passed.
    if (lsm_passes_pc &&
        lsm->address <= pc && pc < lsm->address + advance_address) {
      *lsm_passes_pc = true;
    }

    lsm->address += advance_address;
    lsm->line_num += advance_line;
    lsm->basic_block = true;
    *len = oplen;
    return true;
  }

  // Otherwise, we have the regular opcodes
  switch (opcode) {
    case DW_LNS_copy: {
      lsm->basic_block = false;
      *len = oplen;
      return true;
    }

    case DW_LNS_advance_pc: {
      uint64 advance_address = reader->ReadUnsignedLEB128(start, &templen);
      oplen += templen;

      // Check if the lsm passes "pc". If so, mark it as passed.
      if (lsm_passes_pc && lsm->address <= pc &&
          pc < lsm->address + header.min_insn_length * advance_address) {
        *lsm_passes_pc = true;
      }

      lsm->address += header.min_insn_length * advance_address;
    }
      break;
    case DW_LNS_advance_line: {
      const int64 advance_line = reader->ReadSignedLEB128(start, &templen);
      oplen += templen;
      lsm->line_num += static_cast<int32>(advance_line);

      // With gcc 4.2.1, we can get the line_no here for the first time
      // since DW_LNS_advance_line is called after DW_LNE_set_address is
      // called. So we check if the lsm passes "pc" here, not in
      // DW_LNE_set_address.
      if (lsm_passes_pc && lsm->address == pc) {
        *lsm_passes_pc = true;
      }
    }
      break;
    case DW_LNS_set_file: {
      const uint64 fileno = reader->ReadUnsignedLEB128(start, &templen);
      oplen += templen;
      lsm->file_num = static_cast<uint32>(fileno);
    }
      break;
    case DW_LNS_set_column: {
      const uint64 colno = reader->ReadUnsignedLEB128(start, &templen);
      oplen += templen;
      lsm->column_num = static_cast<uint32>(colno);
    }
      break;
    case DW_LNS_negate_stmt: {
      lsm->is_stmt = !lsm->is_stmt;
    }
      break;
    case DW_LNS_set_basic_block: {
      lsm->basic_block = true;
    }
      break;
    case DW_LNS_fixed_advance_pc: {
      const uint16 advance_address = reader->ReadTwoBytes(start);
      oplen += 2;

      // Check if the lsm passes "pc". If so, mark it as passed.
      if (lsm_passes_pc &&
          lsm->address <= pc && pc < lsm->address + advance_address) {
        *lsm_passes_pc = true;
      }

      lsm->address += advance_address;
    }
      break;
    case DW_LNS_const_add_pc: {
      const int64 advance_address = header.min_insn_length
                                    * ((255 - header.opcode_base)
                                       / header.line_range);

      // Check if the lsm passes "pc". If so, mark it as passed.
      if (lsm_passes_pc &&
          lsm->address <= pc && pc < lsm->address + advance_address) {
        *lsm_passes_pc = true;
      }

      lsm->address += advance_address;
    }
      break;
    case DW_LNS_extended_op: {
      const uint64 extended_op_len = reader->ReadUnsignedLEB128(start,
                                                                &templen);
      start += templen;
      oplen += templen + extended_op_len;

      const uint64 extended_op = reader->ReadOneByte(start);
      start++;

      switch (extended_op) {
        case DW_LNE_end_sequence: {
          lsm->end_sequence = true;
          *len = oplen;
          return true;
        }
          break;
        case DW_LNE_set_address: {
          // With gcc 4.2.1, we cannot tell the line_no here since
          // DW_LNE_set_address is called before DW_LNS_advance_line is
          // called.  So we do not check if the lsm passes "pc" here.  See
          // also the comment in DW_LNS_advance_line.
          uint64 address = reader->ReadAddress(start);
          lsm->address = address;
        }
          break;
        case DW_LNE_define_file: {
          const char *filename = reinterpret_cast<const char *>(start);

          templen = strlen(filename) + 1;
          start += templen;

          uint64 dirindex = reader->ReadUnsignedLEB128(start, &templen);
          oplen += templen;

          const uint64 mod_time = reader->ReadUnsignedLEB128(start,
                                                             &templen);
          oplen += templen;

          const uint64 filelength = reader->ReadUnsignedLEB128(start,
                                                               &templen);
          oplen += templen;

          if (handler) {
            handler->DefineFile(filename, -1, static_cast<uint32>(dirindex), 
                                mod_time, filelength);
          }
        }
          break;
      }
    }
      break;

    default: {
      // Ignore unknown opcode  silently
      if (header.std_opcode_lengths) {
        for (int i = 0; i < (*header.std_opcode_lengths)[opcode]; i++) {
          reader->ReadUnsignedLEB128(start, &templen);
          start += templen;
          oplen += templen;
        }
      }
    }
      break;
  }
  *len = oplen;
  return false;
}