Extend relocation packing to cover arm64.

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.
 
-// LEB128 encoder and decoder for packed ARM relative relocations.
+// SLEB128 encoder and decoder for packed relative relocations.
 //
-// Run-length encoded ARM relative relocations consist of a large number
-// of pairs of relatively small positive integer values.  Encoding these as
-// LEB128 saves space.
+// 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_LEB128_H_
-#define TOOLS_RELOCATION_PACKER_SRC_LEB128_H_
+#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 LEB128 byte stream.
-class Leb128Encoder {
+// Encode packed words as a signed LEB128 byte stream.
+class Sleb128Encoder {
  public:
   // Explicit (but empty) constructor and destructor, for chromium-style.
-  Leb128Encoder();
-  ~Leb128Encoder();
+  Sleb128Encoder();
+  ~Sleb128Encoder();
 
   // Add a value to the encoding stream.
-  // |value| is the unsigned int to add.
-  void Enqueue(ELF::Xword value);
+  // |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 unsigned ints to add.
-  void EnqueueAll(const std::vector<ELF::Xword>& values);
+  // |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 Leb128Decoder {
+class Sleb128Decoder {
  public:
   // Create a new decoder for the given encoded stream.
   // |encoding| is the vector of encoded data.
-  explicit Leb128Decoder(const std::vector<uint8_t>& encoding);
+  explicit Sleb128Decoder(const std::vector<uint8_t>& encoding);
 
   // Explicit (but empty) destructor, for chromium-style.
-  ~Leb128Decoder();
+  ~Sleb128Decoder();
 
   // Retrieve the next value from the encoded stream.
-  ELF::Xword Dequeue();
+  ELF::Sxword Dequeue();
 
   // Retrieve all remaining values from the encoded stream.
   // |values| is the vector of decoded data.
-  void DequeueAll(std::vector<ELF::Xword>* values);
+  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_LEB128_H_
+#endif  // TOOLS_RELOCATION_PACKER_SRC_SLEB128_H_