public:

ByteSource() : ByteSource(nullptr, 0) {}

explicit ByteSource(const string& s) : ByteSource(&s[0], s.size()) {}

ByteSource(const void* data, int size)

: data_(reinterpret_cast<const uint8*>(data)),

size_(size) {

}

ByteSource(const ByteSource& other) = default;

ByteSource(ByteSource&& other) = default;

ByteSource& operator= (const ByteSource& other) = default;

ByteSource& operator= (ByteSource&& other) = default;

// Direct access to the buffer.

template <typename T>

const T* data() const { return reinterpret_cast<const T*>(data_); }

// Gets the buffer size.

int size() const { return size_; }

// Returns true if all the prior "Read" operations were value. Returns false

// if one of the "Read" functions tried to access invalid location.

bool is_error() const { return is_error_; }

// Creates a partial view of the buffer. Trims the range to contain the range

// within this buffer.

ByteSource sub(int offset, int size) const {

if (offset < 0) {

size += offset;

offset = 0;

}

int end = std::min(size_, offset + size);

if (offset > end) {

return ByteSource();

}

return ByteSource(data_ + offset, end - offset);

}

// Reads signed 8 bit integer from the class file BLOB. Raises error and

// returns 0 on invalid offset.

int8 ReadInt8(int offset) {

return ReadRaw<int8>(offset);

}

// Reads unsigned 8 bit integer from the class file BLOB. Raises error and

// returns 0 on invalid offset.

uint8 ReadUInt8(int offset) {

return ReadRaw<uint8>(offset);

}

// Reads signed 16 bit integer from the class file BLOB as big-endian.

// Raises error and returns 0 on invalid offset.

int16 ReadInt16BE(int offset) {

int16 raw_data = ReadRaw<int16>(offset);

#ifdef __APPLE__

return OSSwapBigToHostInt16(raw_data);

#else

return be16toh(raw_data);

#endif

}

// Reads unsigned 16 bit integer from the class file BLOB as big-endian.

// Raises error and returns 0 on invalid offset.

uint16 ReadUInt16BE(int offset) {

uint16 raw_data = ReadRaw<uint16>(offset);

#ifdef __APPLE__

return OSSwapBigToHostInt16(raw_data);

#else

return be16toh(raw_data);

#endif

}

// Reads signed 32 bit integer from the class file BLOB as big-endian.

// Raises error and returns 0 on invalid offset.

int32 ReadInt32BE(int offset) {

int32 raw_data = ReadRaw<int32>(offset);

#ifdef __APPLE__

return OSSwapBigToHostInt32(raw_data);

#else

return be32toh(raw_data);

#endif

}

// Reads signed 64 bit integer from the class file BLOB as big-endian.

// Raises error and returns 0 on invalid offset.

int64 ReadInt64BE(int offset) {

int64 raw_data = ReadRaw<int64>(offset);

#ifdef __APPLE__

return OSSwapBigToHostInt64(raw_data);

#else

return be64toh(raw_data);

#endif

}

private:

// Reads a value from the class file BLOB. Does not convert between

// endianness. Raises error and returns 0 if the offset is invalid.

template <typename T>

T ReadRaw(int offset) {

if ((offset < 0) || (offset + sizeof(T) > size_)) {

DLOG(INFO) << "Bad offset " << offset << " reading ByteSource";

is_error_ = true;

return T();

}

return *reinterpret_cast<const T*>(data_ + offset);

}

private:

// Pointer to the wrapped buffer. Not owned by this class.

const uint8* data_;

// Size of the wrapped buffer in bytes.

int size_;

// True if one of the "Read" functions tried to access invalid location.

bool is_error_ { false };