Update from chromium 62675d9fb31fb8cedc40f68e78e8445a74f362e7

tools/relocation_packer/src/sleb128.h

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// SLEB128 encoder and decoder for packed relative relocations.
+//
+// Delta encoded relative relocations consist of a large number
+// of pairs signed integer values, many with small values.  Encoding these
+// as signed LEB128 saves space.
+//
+// For more on LEB128 see http://en.wikipedia.org/wiki/LEB128.
+
+#ifndef TOOLS_RELOCATION_PACKER_SRC_SLEB128_H_
+#define TOOLS_RELOCATION_PACKER_SRC_SLEB128_H_
+
+#include <stdint.h>
+#include <unistd.h>
+#include <vector>
+
+#include "elf_traits.h"
+
+namespace relocation_packer {
+
+// Encode packed words as a signed LEB128 byte stream.
+class Sleb128Encoder {
+ public:
+  // Explicit (but empty) constructor and destructor, for chromium-style.
+  Sleb128Encoder();
+  ~Sleb128Encoder();
+
+  // Add a value to the encoding stream.
+  // |value| is the signed int to add.
+  void Enqueue(ELF::Sxword value);
+
+  // Add a vector of values to the encoding stream.
+  // |values| is the vector of signed ints to add.
+  void EnqueueAll(const std::vector<ELF::Sxword>& values);
+
+  // Retrieve the encoded representation of the values.
+  // |encoding| is the returned vector of encoded data.
+  void GetEncoding(std::vector<uint8_t>* encoding) { *encoding = encoding_; }
+
+ private:
+  // Growable vector holding the encoded LEB128 stream.
+  std::vector<uint8_t> encoding_;
+};
+
+// Decode a LEB128 byte stream to produce packed words.
+class Sleb128Decoder {
+ public:
+  // Create a new decoder for the given encoded stream.
+  // |encoding| is the vector of encoded data.
+  explicit Sleb128Decoder(const std::vector<uint8_t>& encoding);
+
+  // Explicit (but empty) destructor, for chromium-style.
+  ~Sleb128Decoder();
+
+  // Retrieve the next value from the encoded stream.
+  ELF::Sxword Dequeue();
+
+  // Retrieve all remaining values from the encoded stream.
+  // |values| is the vector of decoded data.
+  void DequeueAll(std::vector<ELF::Sxword>* values);
+
+ private:
+  // Encoded LEB128 stream.
+  std::vector<uint8_t> encoding_;
+
+  // Cursor indicating the current stream retrieval point.
+  size_t cursor_;
+};
+
+}  // namespace relocation_packer
+
+#endif  // TOOLS_RELOCATION_PACKER_SRC_SLEB128_H_