The Tor Browser: comparison toolkit/crashreporter/google-breakpad/src/common/byte

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+// -*- mode: c++ -*-
+// Copyright (c) 2010, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+// Original author: Jim Blandy <jimb@mozilla.com> <jimb@red-bean.com>
+// byte_cursor.h: Classes for parsing values from a buffer of bytes.
+// The ByteCursor class provides a convenient interface for reading
+// fixed-size integers of arbitrary endianness, being thorough about
+// checking for buffer overruns.
+#ifndef COMMON_BYTE_CURSOR_H_
+#define COMMON_BYTE_CURSOR_H_
+#include <assert.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <string>
+#include "common/using_std_string.h"
+namespace google_breakpad {
+// A buffer holding a series of bytes.
+struct ByteBuffer {
+ByteBuffer() : start(0), end(0) { }
+ByteBuffer(const uint8_t *set_start, size_t set_size)
+: start(set_start), end(set_start + set_size) { }
+~ByteBuffer() { };
+// Equality operators. Useful in unit tests, and when we're using
+// ByteBuffers to refer to regions of a larger buffer.
+bool operator==(const ByteBuffer &that) const {
+return start == that.start && end == that.end;
+}
+bool operator!=(const ByteBuffer &that) const {
+return start != that.start || end != that.end;
+}
+// Not C++ style guide compliant, but this definitely belongs here.
+size_t Size() const {
+assert(start <= end);
+return end - start;
+}
+const uint8_t *start, *end;
+};
+// A cursor pointing into a ByteBuffer that can parse numbers of various
+// widths and representations, strings, and data blocks, advancing through
+// the buffer as it goes. All ByteCursor operations check that accesses
+// haven't gone beyond the end of the enclosing ByteBuffer.
+class ByteCursor {
+public:
+// Create a cursor reading bytes from the start of BUFFER. By default, the
+// cursor reads multi-byte values in little-endian form.
+ByteCursor(const ByteBuffer *buffer, bool big_endian = false)
+: buffer_(buffer), here_(buffer->start),
+big_endian_(big_endian), complete_(true) { }
+// Accessor and setter for this cursor's endianness flag.
+bool big_endian() const { return big_endian_; }
+void set_big_endian(bool big_endian) { big_endian_ = big_endian; }
+// Accessor and setter for this cursor's current position. The setter
+// returns a reference to this cursor.
+const uint8_t *here() const { return here_; }
+ByteCursor &set_here(const uint8_t *here) {
+assert(buffer_->start <= here && here <= buffer_->end);
+here_ = here;
+return *this;
+}
+// Return the number of bytes available to read at the cursor.
+size_t Available() const { return size_t(buffer_->end - here_); }
+// Return true if this cursor is at the end of its buffer.
+bool AtEnd() const { return Available() == 0; }
+// When used as a boolean value this cursor converts to true if all
+// prior reads have been completed, or false if we ran off the end
+// of the buffer.
+operator bool() const { return complete_; }
+// Read a SIZE-byte integer at this cursor, signed if IS_SIGNED is true,
+// unsigned otherwise, using the cursor's established endianness, and set
+// *RESULT to the number. If we read off the end of our buffer, clear
+// this cursor's complete_ flag, and store a dummy value in *RESULT.
+// Return a reference to this cursor.
+template<typename T>
+ByteCursor &Read(size_t size, bool is_signed, T *result) {
+if (CheckAvailable(size)) {
+T v = 0;
+if (big_endian_) {
+for (size_t i = 0; i < size; i++)
+v = (v << 8) + here_[i];
+} else {
+// This loop condition looks weird, but size_t is unsigned, so
+// decrementing i after it is zero yields the largest size_t value.
+for (size_t i = size - 1; i < size; i--)
+v = (v << 8) + here_[i];
+}
+if (is_signed && size < sizeof(T)) {
+size_t sign_bit = (T)1 << (size * 8 - 1);
+v = (v ^ sign_bit) - sign_bit;
+}
+here_ += size;
+*result = v;
+} else {
+*result = (T) 0xdeadbeef;
+}
+return *this;
+}
+// Read an integer, using the cursor's established endianness and
+// *RESULT's size and signedness, and set *RESULT to the number. If we
+// read off the end of our buffer, clear this cursor's complete_ flag.
+// Return a reference to this cursor.
+template<typename T>
+ByteCursor &operator>>(T &result) {
+bool T_is_signed = (T)-1 < 0;
+return Read(sizeof(T), T_is_signed, &result);
+}
+// Copy the SIZE bytes at the cursor to BUFFER, and advance this
+// cursor to the end of them. If we read off the end of our buffer,
+// clear this cursor's complete_ flag, and set *POINTER to NULL.
+// Return a reference to this cursor.
+ByteCursor &Read(uint8_t *buffer, size_t size) {
+if (CheckAvailable(size)) {
+memcpy(buffer, here_, size);
+here_ += size;
+}
+return *this;
+}
+// Set STR to a copy of the '\0'-terminated string at the cursor. If the
+// byte buffer does not contain a terminating zero, clear this cursor's
+// complete_ flag, and set STR to the empty string. Return a reference to
+// this cursor.
+ByteCursor &CString(string *str) {
+const uint8_t *end
+= static_cast<const uint8_t *>(memchr(here_, '\0', Available()));
+if (end) {
+str->assign(reinterpret_cast<const char *>(here_), end - here_);
+here_ = end + 1;
+} else {
+str->clear();
+here_ = buffer_->end;
+complete_ = false;
+}
+return *this;
+}
+// Like CString(STR), but extract the string from a fixed-width buffer
+// LIMIT bytes long, which may or may not contain a terminating '\0'
+// byte. Specifically:
+//
+// - If there are not LIMIT bytes available at the cursor, clear the
+//   cursor's complete_ flag and set STR to the empty string.
+//
+// - Otherwise, if the LIMIT bytes at the cursor contain any '\0'
+//   characters, set *STR to a copy of the bytes before the first '\0',
+//   and advance the cursor by LIMIT bytes.
+//
+// - Otherwise, set *STR to a copy of those LIMIT bytes, and advance the
+//   cursor by LIMIT bytes.
+ByteCursor &CString(string *str, size_t limit) {
+if (CheckAvailable(limit)) {
+const uint8_t *end
+= static_cast<const uint8_t *>(memchr(here_, '\0', limit));
+if (end)
+str->assign(reinterpret_cast<const char *>(here_), end - here_);
+else
+str->assign(reinterpret_cast<const char *>(here_), limit);
+here_ += limit;
+} else {
+str->clear();
+}
+return *this;
+}
+// Set *POINTER to point to the SIZE bytes at the cursor, and advance
+// this cursor to the end of them. If SIZE is omitted, don't move the
+// cursor. If we read off the end of our buffer, clear this cursor's
+// complete_ flag, and set *POINTER to NULL. Return a reference to this
+// cursor.
+ByteCursor &PointTo(const uint8_t **pointer, size_t size = 0) {
+if (CheckAvailable(size)) {
+*pointer = here_;
+here_ += size;
+} else {
+*pointer = NULL;
+}
+return *this;
+}
+// Skip SIZE bytes at the cursor. If doing so would advance us off
+// the end of our buffer, clear this cursor's complete_ flag, and
+// set *POINTER to NULL. Return a reference to this cursor.
+ByteCursor &Skip(size_t size) {
+if (CheckAvailable(size))
+here_ += size;
+return *this;
+}
+private:
+// If there are at least SIZE bytes available to read from the buffer,
+// return true. Otherwise, set here_ to the end of the buffer, set
+// complete_ to false, and return false.
+bool CheckAvailable(size_t size) {
+if (Available() >= size) {
+return true;
+} else {
+here_ = buffer_->end;
+complete_ = false;
+return false;
+}
+}
+// The buffer we're reading bytes from.
+const ByteBuffer *buffer_;
+// The next byte within buffer_ that we'll read.
+const uint8_t *here_;
+// True if we should read numbers in big-endian form; false if we
+// should read in little-endian form.
+bool big_endian_;
+// True if we've been able to read all we've been asked to.
+bool complete_;
+};
+}  // namespace google_breakpad
+#endif  // COMMON_BYTE_CURSOR_H_

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comparison: toolkit/crashreporter/google-breakpad/src/common/byte_cursor.h

toolkit/crashreporter/google-breakpad/src/common/byte_cursor.h