1 files changed, 114 insertions, 0 deletions
diff --git a/src/decodetable.cc b/src/decodetable.cc
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+++ b/src/decodetable.cc
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+// Copyright 2008 Google Inc.
+// Author: Lincoln Smith
+//
+// 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.
+//
+// VCDiffCodeTableReader is a class to interpret a stream of opcodes
+// as VCDIFF instruction types, based on a VCDiffCodeTableData structure.
+
+#include <config.h>
+#include "decodetable.h"
+#include "codetable.h"
+#include "logging.h"
+#include "varint_bigendian.h"
+#include "vcdiff_defs.h"
+
+namespace open_vcdiff {
+
+VCDiffCodeTableReader::VCDiffCodeTableReader()
+    : code_table_data_(&VCDiffCodeTableData::kDefaultCodeTableData),
+      non_default_code_table_data_(NULL),
+      instructions_and_sizes_(NULL),
+      instructions_and_sizes_end_(NULL),
+      last_instruction_start_(NULL),
+      pending_second_instruction_(kNoOpcode),
+      last_pending_second_instruction_(kNoOpcode) {
+}
+
+bool VCDiffCodeTableReader::UseCodeTable(
+    const VCDiffCodeTableData& code_table_data, unsigned char max_mode) {
+  if (!code_table_data.Validate(max_mode)) return false;
+  if (!non_default_code_table_data_.get()) {
+    non_default_code_table_data_.reset(new VCDiffCodeTableData);
+  }
+  *non_default_code_table_data_ = code_table_data;
+  code_table_data_ = non_default_code_table_data_.get();
+  return true;
+}
+
+VCDiffInstructionType VCDiffCodeTableReader::GetNextInstruction(
+    int32_t* size,
+    unsigned char* mode) {
+  if (!instructions_and_sizes_) {
+    VCD_ERROR << "Internal error: GetNextInstruction() called before Init()"
+              << VCD_ENDL;
+    return VCD_INSTRUCTION_ERROR;
+  }
+  last_instruction_start_ = *instructions_and_sizes_;
+  last_pending_second_instruction_ = pending_second_instruction_;
+  unsigned char opcode = 0;
+  unsigned char instruction_type = VCD_NOOP;
+  int32_t instruction_size = 0;
+  unsigned char instruction_mode = 0;
+  do {
+    if (pending_second_instruction_ != kNoOpcode) {
+      // There is a second instruction left over
+      // from the most recently processed opcode.
+      opcode = static_cast<unsigned char>(pending_second_instruction_);
+      pending_second_instruction_ = kNoOpcode;
+      instruction_type = code_table_data_->inst2[opcode];
+      instruction_size = code_table_data_->size2[opcode];
+      instruction_mode = code_table_data_->mode2[opcode];
+      break;
+    }
+    if (*instructions_and_sizes_ >= instructions_and_sizes_end_) {
+      // Ran off end of instruction stream
+      return VCD_INSTRUCTION_END_OF_DATA;
+    }
+    opcode = **instructions_and_sizes_;
+    if (code_table_data_->inst2[opcode] != VCD_NOOP) {
+      // This opcode contains two instructions; process the first one now, and
+      // save a pointer to the second instruction, which should be returned
+      // by the next call to GetNextInstruction
+      pending_second_instruction_ = **instructions_and_sizes_;
+    }
+    ++(*instructions_and_sizes_);
+    instruction_type = code_table_data_->inst1[opcode];
+    instruction_size = code_table_data_->size1[opcode];
+    instruction_mode = code_table_data_->mode1[opcode];
+  // This do-while loop is necessary in case inst1 == VCD_NOOP for an opcode
+  // that was actually used in the encoding.  That case is unusual, but it
+  // is not prohibited by the standard.
+  } while (instruction_type == VCD_NOOP);
+  if (instruction_size == 0) {
+    // Parse the size as a Varint in the instruction stream.
+    switch (*size = VarintBE<int32_t>::Parse(instructions_and_sizes_end_,
+                                             instructions_and_sizes_)) {
+      case RESULT_ERROR:
+        VCD_ERROR << "Instruction size is not a valid variable-length integer"
+                  << VCD_ENDL;
+        return VCD_INSTRUCTION_ERROR;
+      case RESULT_END_OF_DATA:
+        UnGetInstruction();  // Rewind to instruction start
+        return VCD_INSTRUCTION_END_OF_DATA;
+      default:
+        break;  // Successfully parsed Varint
+    }
+  } else {
+    *size = instruction_size;
+  }
+  *mode = instruction_mode;
+  return static_cast<VCDiffInstructionType>(instruction_type);
+}
+
+};  // namespace open_vcdiff