The Tor Browser: js/src/jit/CompactBuffer.h@6474c204b198 (annotated)

js/src/jit/CompactBuffer.h@6474c204b198 (annotated)

js/src/jit/CompactBuffer.h

Wed, 31 Dec 2014 06:09:35 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:09:35 +0100
changeset 0: 6474c204b198
permissions: -rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
  * vim: set ts=8 sts=4 et sw=4 tw=99:
  * This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 #ifndef jit_Compactbuffer_h
 #define jit_Compactbuffer_h
 #include "jsalloc.h"
 #include "jit/IonTypes.h"
 #include "js/Vector.h"
 namespace js {
 namespace jit {
 class CompactBufferWriter;
 // CompactBuffers are byte streams designed for compressable integers. It has
 // helper functions for writing bytes, fixed-size integers, and variable-sized
 // integers. Variable sized integers are encoded in 1-5 bytes, each byte
 // containing 7 bits of the integer and a bit which specifies whether the next
 // byte is also part of the integer.
 //
 // Fixed-width integers are also available, in case the actual value will not
 // be known until later.
 class CompactBufferReader
 {
     const uint8_t *buffer_;
     const uint8_t *end_;
     uint32_t readVariableLength() {
         uint32_t val = 0;
         uint32_t shift = 0;
         uint8_t byte;
         while (true) {
             JS_ASSERT(shift < 32);
             byte = readByte();
             val |= (uint32_t(byte) >> 1) << shift;
             shift += 7;
             if (!(byte & 1))
                 return val;
         }
         MOZ_ASSUME_UNREACHABLE("unreachable");
     }
   public:
     CompactBufferReader(const uint8_t *start, const uint8_t *end)
       : buffer_(start),
         end_(end)
     { }
     inline CompactBufferReader(const CompactBufferWriter &writer);
     uint8_t readByte() {
         JS_ASSERT(buffer_ < end_);
         return *buffer_++;
     }
     uint32_t readFixedUint32_t() {
         uint32_t b0 = readByte();
         uint32_t b1 = readByte();
         uint32_t b2 = readByte();
         uint32_t b3 = readByte();
         return b0 | (b1 << 8) | (b2 << 16) | (b3 << 24);
     }
     uint16_t readFixedUint16_t() {
         uint32_t b0 = readByte();
         uint32_t b1 = readByte();
         return b0 | (b1 << 8);
     }
     uint32_t readUnsigned() {
         return readVariableLength();
     }
     int32_t readSigned() {
         uint8_t b = readByte();
         bool isNegative = !!(b & (1 << 0));
         bool more = !!(b & (1 << 1));
         int32_t result = b >> 2;
         if (more)
             result |= readUnsigned() << 6;
         if (isNegative)
             return -result;
         return result;
     }
     bool more() const {
         JS_ASSERT(buffer_ <= end_);
         return buffer_ < end_;
     }
     void seek(const uint8_t *start, uint32_t offset) {
         buffer_ = start + offset;
         MOZ_ASSERT(start < end_);
         MOZ_ASSERT(buffer_ < end_);
     }
 };
 class CompactBufferWriter
 {
     js::Vector<uint8_t, 32, SystemAllocPolicy> buffer_;
     bool enoughMemory_;
   public:
     CompactBufferWriter()
       : enoughMemory_(true)
     { }
     // Note: writeByte() takes uint32 to catch implicit casts with a runtime
     // assert.
     void writeByte(uint32_t byte) {
         JS_ASSERT(byte <= 0xFF);
         enoughMemory_ &= buffer_.append(byte);
     }
     void writeUnsigned(uint32_t value) {
         do {
             uint8_t byte = ((value & 0x7F) << 1) | (value > 0x7F);
             writeByte(byte);
             value >>= 7;
         } while (value);
     }
     void writeSigned(int32_t v) {
         bool isNegative = v < 0;
         uint32_t value = isNegative ? -v : v;
         uint8_t byte = ((value & 0x3F) << 2) | ((value > 0x3F) << 1) | uint32_t(isNegative);
         writeByte(byte);
         // Write out the rest of the bytes, if needed.
         value >>= 6;
         if (value == 0)
             return;
         writeUnsigned(value);
     }
     void writeFixedUint32_t(uint32_t value) {
         writeByte(value & 0xFF);
         writeByte((value >> 8) & 0xFF);
         writeByte((value >> 16) & 0xFF);
         writeByte((value >> 24) & 0xFF);
     }
     void writeFixedUint16_t(uint16_t value) {
         writeByte(value & 0xFF);
         writeByte(value >> 8);
     }
     size_t length() const {
         return buffer_.length();
     }
     uint8_t *buffer() {
         return &buffer_[0];
     }
     const uint8_t *buffer() const {
         return &buffer_[0];
     }
     bool oom() const {
         return !enoughMemory_;
     }
 };
 CompactBufferReader::CompactBufferReader(const CompactBufferWriter &writer)
   : buffer_(writer.buffer()),
     end_(writer.buffer() + writer.length())
 {
 }
 } // namespace jit
 } // namespace js
 #endif /* jit_Compactbuffer_h */

The Tor Browser / annotate

js/src/jit/CompactBuffer.h@6474c204b198 (annotated)

js/src/jit/CompactBuffer.h