1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/toolkit/crashreporter/google-breakpad/src/common/byte_cursor.h Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,265 @@
1.4 +// -*- mode: c++ -*-
1.5 +
1.6 +// Copyright (c) 2010, Google Inc.
1.7 +// All rights reserved.
1.8 +//
1.9 +// Redistribution and use in source and binary forms, with or without
1.10 +// modification, are permitted provided that the following conditions are
1.11 +// met:
1.12 +//
1.13 +// * Redistributions of source code must retain the above copyright
1.14 +// notice, this list of conditions and the following disclaimer.
1.15 +// * Redistributions in binary form must reproduce the above
1.16 +// copyright notice, this list of conditions and the following disclaimer
1.17 +// in the documentation and/or other materials provided with the
1.18 +// distribution.
1.19 +// * Neither the name of Google Inc. nor the names of its
1.20 +// contributors may be used to endorse or promote products derived from
1.21 +// this software without specific prior written permission.
1.22 +//
1.23 +// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
1.24 +// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
1.25 +// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
1.26 +// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
1.27 +// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
1.28 +// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
1.29 +// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
1.30 +// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
1.31 +// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
1.32 +// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
1.33 +// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
1.34 +
1.35 +// Original author: Jim Blandy <jimb@mozilla.com> <jimb@red-bean.com>
1.36 +
1.37 +// byte_cursor.h: Classes for parsing values from a buffer of bytes.
1.38 +// The ByteCursor class provides a convenient interface for reading
1.39 +// fixed-size integers of arbitrary endianness, being thorough about
1.40 +// checking for buffer overruns.
1.41 +
1.42 +#ifndef COMMON_BYTE_CURSOR_H_
1.43 +#define COMMON_BYTE_CURSOR_H_
1.44 +
1.45 +#include <assert.h>
1.46 +#include <stdint.h>
1.47 +#include <stdlib.h>
1.48 +#include <string.h>
1.49 +#include <string>
1.50 +
1.51 +#include "common/using_std_string.h"
1.52 +
1.53 +namespace google_breakpad {
1.54 +
1.55 +// A buffer holding a series of bytes.
1.56 +struct ByteBuffer {
1.57 + ByteBuffer() : start(0), end(0) { }
1.58 + ByteBuffer(const uint8_t *set_start, size_t set_size)
1.59 + : start(set_start), end(set_start + set_size) { }
1.60 + ~ByteBuffer() { };
1.61 +
1.62 + // Equality operators. Useful in unit tests, and when we're using
1.63 + // ByteBuffers to refer to regions of a larger buffer.
1.64 + bool operator==(const ByteBuffer &that) const {
1.65 + return start == that.start && end == that.end;
1.66 + }
1.67 + bool operator!=(const ByteBuffer &that) const {
1.68 + return start != that.start || end != that.end;
1.69 + }
1.70 +
1.71 + // Not C++ style guide compliant, but this definitely belongs here.
1.72 + size_t Size() const {
1.73 + assert(start <= end);
1.74 + return end - start;
1.75 + }
1.76 +
1.77 + const uint8_t *start, *end;
1.78 +};
1.79 +
1.80 +// A cursor pointing into a ByteBuffer that can parse numbers of various
1.81 +// widths and representations, strings, and data blocks, advancing through
1.82 +// the buffer as it goes. All ByteCursor operations check that accesses
1.83 +// haven't gone beyond the end of the enclosing ByteBuffer.
1.84 +class ByteCursor {
1.85 + public:
1.86 + // Create a cursor reading bytes from the start of BUFFER. By default, the
1.87 + // cursor reads multi-byte values in little-endian form.
1.88 + ByteCursor(const ByteBuffer *buffer, bool big_endian = false)
1.89 + : buffer_(buffer), here_(buffer->start),
1.90 + big_endian_(big_endian), complete_(true) { }
1.91 +
1.92 + // Accessor and setter for this cursor's endianness flag.
1.93 + bool big_endian() const { return big_endian_; }
1.94 + void set_big_endian(bool big_endian) { big_endian_ = big_endian; }
1.95 +
1.96 + // Accessor and setter for this cursor's current position. The setter
1.97 + // returns a reference to this cursor.
1.98 + const uint8_t *here() const { return here_; }
1.99 + ByteCursor &set_here(const uint8_t *here) {
1.100 + assert(buffer_->start <= here && here <= buffer_->end);
1.101 + here_ = here;
1.102 + return *this;
1.103 + }
1.104 +
1.105 + // Return the number of bytes available to read at the cursor.
1.106 + size_t Available() const { return size_t(buffer_->end - here_); }
1.107 +
1.108 + // Return true if this cursor is at the end of its buffer.
1.109 + bool AtEnd() const { return Available() == 0; }
1.110 +
1.111 + // When used as a boolean value this cursor converts to true if all
1.112 + // prior reads have been completed, or false if we ran off the end
1.113 + // of the buffer.
1.114 + operator bool() const { return complete_; }
1.115 +
1.116 + // Read a SIZE-byte integer at this cursor, signed if IS_SIGNED is true,
1.117 + // unsigned otherwise, using the cursor's established endianness, and set
1.118 + // *RESULT to the number. If we read off the end of our buffer, clear
1.119 + // this cursor's complete_ flag, and store a dummy value in *RESULT.
1.120 + // Return a reference to this cursor.
1.121 + template<typename T>
1.122 + ByteCursor &Read(size_t size, bool is_signed, T *result) {
1.123 + if (CheckAvailable(size)) {
1.124 + T v = 0;
1.125 + if (big_endian_) {
1.126 + for (size_t i = 0; i < size; i++)
1.127 + v = (v << 8) + here_[i];
1.128 + } else {
1.129 + // This loop condition looks weird, but size_t is unsigned, so
1.130 + // decrementing i after it is zero yields the largest size_t value.
1.131 + for (size_t i = size - 1; i < size; i--)
1.132 + v = (v << 8) + here_[i];
1.133 + }
1.134 + if (is_signed && size < sizeof(T)) {
1.135 + size_t sign_bit = (T)1 << (size * 8 - 1);
1.136 + v = (v ^ sign_bit) - sign_bit;
1.137 + }
1.138 + here_ += size;
1.139 + *result = v;
1.140 + } else {
1.141 + *result = (T) 0xdeadbeef;
1.142 + }
1.143 + return *this;
1.144 + }
1.145 +
1.146 + // Read an integer, using the cursor's established endianness and
1.147 + // *RESULT's size and signedness, and set *RESULT to the number. If we
1.148 + // read off the end of our buffer, clear this cursor's complete_ flag.
1.149 + // Return a reference to this cursor.
1.150 + template<typename T>
1.151 + ByteCursor &operator>>(T &result) {
1.152 + bool T_is_signed = (T)-1 < 0;
1.153 + return Read(sizeof(T), T_is_signed, &result);
1.154 + }
1.155 +
1.156 + // Copy the SIZE bytes at the cursor to BUFFER, and advance this
1.157 + // cursor to the end of them. If we read off the end of our buffer,
1.158 + // clear this cursor's complete_ flag, and set *POINTER to NULL.
1.159 + // Return a reference to this cursor.
1.160 + ByteCursor &Read(uint8_t *buffer, size_t size) {
1.161 + if (CheckAvailable(size)) {
1.162 + memcpy(buffer, here_, size);
1.163 + here_ += size;
1.164 + }
1.165 + return *this;
1.166 + }
1.167 +
1.168 + // Set STR to a copy of the '\0'-terminated string at the cursor. If the
1.169 + // byte buffer does not contain a terminating zero, clear this cursor's
1.170 + // complete_ flag, and set STR to the empty string. Return a reference to
1.171 + // this cursor.
1.172 + ByteCursor &CString(string *str) {
1.173 + const uint8_t *end
1.174 + = static_cast<const uint8_t *>(memchr(here_, '\0', Available()));
1.175 + if (end) {
1.176 + str->assign(reinterpret_cast<const char *>(here_), end - here_);
1.177 + here_ = end + 1;
1.178 + } else {
1.179 + str->clear();
1.180 + here_ = buffer_->end;
1.181 + complete_ = false;
1.182 + }
1.183 + return *this;
1.184 + }
1.185 +
1.186 + // Like CString(STR), but extract the string from a fixed-width buffer
1.187 + // LIMIT bytes long, which may or may not contain a terminating '\0'
1.188 + // byte. Specifically:
1.189 + //
1.190 + // - If there are not LIMIT bytes available at the cursor, clear the
1.191 + // cursor's complete_ flag and set STR to the empty string.
1.192 + //
1.193 + // - Otherwise, if the LIMIT bytes at the cursor contain any '\0'
1.194 + // characters, set *STR to a copy of the bytes before the first '\0',
1.195 + // and advance the cursor by LIMIT bytes.
1.196 + //
1.197 + // - Otherwise, set *STR to a copy of those LIMIT bytes, and advance the
1.198 + // cursor by LIMIT bytes.
1.199 + ByteCursor &CString(string *str, size_t limit) {
1.200 + if (CheckAvailable(limit)) {
1.201 + const uint8_t *end
1.202 + = static_cast<const uint8_t *>(memchr(here_, '\0', limit));
1.203 + if (end)
1.204 + str->assign(reinterpret_cast<const char *>(here_), end - here_);
1.205 + else
1.206 + str->assign(reinterpret_cast<const char *>(here_), limit);
1.207 + here_ += limit;
1.208 + } else {
1.209 + str->clear();
1.210 + }
1.211 + return *this;
1.212 + }
1.213 +
1.214 + // Set *POINTER to point to the SIZE bytes at the cursor, and advance
1.215 + // this cursor to the end of them. If SIZE is omitted, don't move the
1.216 + // cursor. If we read off the end of our buffer, clear this cursor's
1.217 + // complete_ flag, and set *POINTER to NULL. Return a reference to this
1.218 + // cursor.
1.219 + ByteCursor &PointTo(const uint8_t **pointer, size_t size = 0) {
1.220 + if (CheckAvailable(size)) {
1.221 + *pointer = here_;
1.222 + here_ += size;
1.223 + } else {
1.224 + *pointer = NULL;
1.225 + }
1.226 + return *this;
1.227 + }
1.228 +
1.229 + // Skip SIZE bytes at the cursor. If doing so would advance us off
1.230 + // the end of our buffer, clear this cursor's complete_ flag, and
1.231 + // set *POINTER to NULL. Return a reference to this cursor.
1.232 + ByteCursor &Skip(size_t size) {
1.233 + if (CheckAvailable(size))
1.234 + here_ += size;
1.235 + return *this;
1.236 + }
1.237 +
1.238 + private:
1.239 + // If there are at least SIZE bytes available to read from the buffer,
1.240 + // return true. Otherwise, set here_ to the end of the buffer, set
1.241 + // complete_ to false, and return false.
1.242 + bool CheckAvailable(size_t size) {
1.243 + if (Available() >= size) {
1.244 + return true;
1.245 + } else {
1.246 + here_ = buffer_->end;
1.247 + complete_ = false;
1.248 + return false;
1.249 + }
1.250 + }
1.251 +
1.252 + // The buffer we're reading bytes from.
1.253 + const ByteBuffer *buffer_;
1.254 +
1.255 + // The next byte within buffer_ that we'll read.
1.256 + const uint8_t *here_;
1.257 +
1.258 + // True if we should read numbers in big-endian form; false if we
1.259 + // should read in little-endian form.
1.260 + bool big_endian_;
1.261 +
1.262 + // True if we've been able to read all we've been asked to.
1.263 + bool complete_;
1.264 +};
1.265 +
1.266 +} // namespace google_breakpad
1.267 +
1.268 +#endif // COMMON_BYTE_CURSOR_H_
