woff2/buffer.h

// Copyright 2013 Google Inc. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// The parts of ots.h & opentype-sanitiser.h that we need, taken from the
// https://code.google.com/p/ots/ project.

#ifndef WOFF2_BUFFER_H_
#define WOFF2_BUFFER_H_

#include <stdint.h>
#include <arpa/inet.h>
#include <cstdlib>
#include <cstring>
#include <limits>

namespace woff2 {

#if defined(_MSC_VER) || !defined(FONT_COMPRESSION_DEBUG)
#define FONT_COMPRESSION_FAILURE() false
#else
#define FONT_COMPRESSION_FAILURE() \
  util::compression::font::Failure(__FILE__, __LINE__, __PRETTY_FUNCTION__)
inline bool Failure(const char *f, int l, const char *fn) {
  std::fprintf(stderr, "ERROR at %s:%d (%s)\n", f, l, fn);
  std::fflush(stderr);
  return false;
}
#endif

// -----------------------------------------------------------------------------
// Buffer helper class
//
// This class perform some trival buffer operations while checking for
// out-of-bounds errors. As a family they return false if anything is amiss,
// updating the current offset otherwise.
// -----------------------------------------------------------------------------
class Buffer {
 public:
  Buffer(const uint8_t *buffer, size_t len)
      : buffer_(buffer),
        length_(len),
        offset_(0) { }

  bool Skip(size_t n_bytes) {
    return Read(NULL, n_bytes);
  }

  bool Read(uint8_t *buffer, size_t n_bytes) {
    if (n_bytes > 1024 * 1024 * 1024) {
      return FONT_COMPRESSION_FAILURE();
    }
    if ((offset_ + n_bytes > length_) ||
        (offset_ > length_ - n_bytes)) {
      return FONT_COMPRESSION_FAILURE();
    }
    if (buffer) {
      std::memcpy(buffer, buffer_ + offset_, n_bytes);
    }
    offset_ += n_bytes;
    return true;
  }

  inline bool ReadU8(uint8_t *value) {
    if (offset_ + 1 > length_) {
      return FONT_COMPRESSION_FAILURE();
    }
    *value = buffer_[offset_];
    ++offset_;
    return true;
  }

  bool ReadU16(uint16_t *value) {
    if (offset_ + 2 > length_) {
      return FONT_COMPRESSION_FAILURE();
    }
    std::memcpy(value, buffer_ + offset_, sizeof(uint16_t));
    *value = ntohs(*value);
    offset_ += 2;
    return true;
  }

  bool ReadS16(int16_t *value) {
    return ReadU16(reinterpret_cast<uint16_t*>(value));
  }

  bool ReadU24(uint32_t *value) {
    if (offset_ + 3 > length_) {
      return FONT_COMPRESSION_FAILURE();
    }
    *value = static_cast<uint32_t>(buffer_[offset_]) << 16 |
        static_cast<uint32_t>(buffer_[offset_ + 1]) << 8 |
        static_cast<uint32_t>(buffer_[offset_ + 2]);
    offset_ += 3;
    return true;
  }

  bool ReadU32(uint32_t *value) {
    if (offset_ + 4 > length_) {
      return FONT_COMPRESSION_FAILURE();
    }
    std::memcpy(value, buffer_ + offset_, sizeof(uint32_t));
    *value = ntohl(*value);
    offset_ += 4;
    return true;
  }

  bool ReadS32(int32_t *value) {
    return ReadU32(reinterpret_cast<uint32_t*>(value));
  }

  bool ReadTag(uint32_t *value) {
    if (offset_ + 4 > length_) {
      return FONT_COMPRESSION_FAILURE();
    }
    std::memcpy(value, buffer_ + offset_, sizeof(uint32_t));
    offset_ += 4;
    return true;
  }

  bool ReadR64(uint64_t *value) {
    if (offset_ + 8 > length_) {
      return FONT_COMPRESSION_FAILURE();
    }
    std::memcpy(value, buffer_ + offset_, sizeof(uint64_t));
    offset_ += 8;
    return true;
  }

  const uint8_t *buffer() const { return buffer_; }
  size_t offset() const { return offset_; }
  size_t length() const { return length_; }

  void set_offset(size_t newoffset) { offset_ = newoffset; }

 private:
  const uint8_t * const buffer_;
  const size_t length_;
  size_t offset_;
};

} // namespace woff2

#endif  // WOFF2_BUFFER_H_