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

toolkit/crashreporter/google-breakpad/src/common/byte_cursor.h@b8a032363ba2 (annotated)

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

Thu, 22 Jan 2015 13:21:57 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Thu, 22 Jan 2015 13:21:57 +0100
branch: TOR_BUG_9701
changeset 15: b8a032363ba2
permissions: -rw-r--r--

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

 // -*- 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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toolkit/crashreporter/google-breakpad/src/common/byte_cursor.h@b8a032363ba2 (annotated)

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