/// <summary>
/// Read a given number of bytes from the current stream position
/// </summary>
/// <param name="position">Position in the carrier stream</param>
/// <param name="buffer">Byte array to populate while reading stream</param>
/// <param name="offset">Zero-based byte offset in buffer at which to begin storing the data</param>
/// <param name="count">The maximum number of bytes to be read from the current stream</param>
/// <returns>The total number of bytes read into the buffer</returns>
public override int Read(long position, byte[] buffer, int offset, int count)
{
int backingCount = count * 8 * _fileHeader.BytesPerPixel;
BackingStream.Position = _fileHeader.BitmapOffset + (position * 8 * _fileHeader.BytesPerPixel);
byte[] carrierValues = new byte[backingCount];
BackingStream.Read(carrierValues, 0, backingCount);
int read = 0;
int readIndex = 0;
for (int i = 0, carrierIndex = 0; i < count * 8; ++i, carrierIndex += _fileHeader.BytesPerPixel)
{
read = read << 1;
read |= carrierValues[carrierIndex] & 0x01;
if (i == 0 || (i + 1) % 8 != 0)
{
continue;
}
buffer[readIndex + offset] = (byte)read;
read = 0;
++readIndex;
}
return(readIndex);
}
/// <summary>
/// Read a given number of bytes from the current stream position
/// </summary>
/// <param name="position">Position in the carrier stream</param>
/// <param name="buffer">Byte array to populate while reading stream</param>
/// <param name="offset">Zero-based byte offset in buffer at which to begin storing the data</param>
/// <param name="count">The maximum number of bytes to be read from the current stream</param>
/// <returns>The total number of bytes read into the buffer</returns>
public override int Read(long position, byte[] buffer, int offset, int count)
{
BackingStream.Position = position + HEADER_LENGTH;
Logger.Debug(h => h("Read: Position = {0}, Offset = {1}, Count = {2}",
BackingStream.Position, offset, count));
return(BackingStream.Read(buffer, offset, count));
}
public byte[] Read(long address, int length)
{
if (length == 0)
{
}
byte[] result = new byte[length];
BackingStream.Seek(address, SeekOrigin.Begin);
BackingStream.Read(result, 0, length);
return(result);
}
/// <summary>
/// Write a given number of bytes from the current stream position
/// </summary>
/// <param name="position">Position in the carrier stream</param>
/// <param name="buffer">Byte array to write to the current stream position</param>
/// <param name="offset">Zero-based byte offset in buffer at which to begin reading the data</param>
/// <param name="count">The maximum number of bytes to be read from the buffer</param>
/// <remarks>
/// http://graphics.stanford.edu/~seander/bithacks.html#ConditionalSetOrClearBitsWithoutBranching
/// </remarks>
public override void Write(long position, byte[] buffer, int offset, int count)
{
int pixelCount = count * 8 * _fileHeader.BytesPerPixel;
BackingStream.Position = _fileHeader.BitmapOffset + (position * 8 * _fileHeader.BytesPerPixel);
byte[] pixels = new byte[pixelCount];
if (BackingStream.Read(pixels, 0, pixelCount) != pixelCount)
{
throw new InvalidOperationException(
string.Format("Unable to read enough carrier pixels for writing, {0}bytes", pixelCount));
}
int pixelIndex = 0;
for (int i = 0; i < count; ++i)
{
//Reverse the byte, so the value isn't written backwards
// http://stackoverflow.com/a/2602885
byte reverse = (byte)((buffer[offset + i] & 0xF0) >> 4 | (buffer[offset + i] & 0x0F) << 4);
reverse = (byte)((reverse & 0xCC) >> 2 | (reverse & 0x33) << 2);
reverse = (byte)((reverse & 0xAA) >> 1 | (reverse & 0x55) << 1);
int writeIndex = 0;
while (writeIndex < 8)
{
//http://graphics.stanford.edu/~seander/bithacks.html#ConditionalSetOrClearBitsWithoutBranching
pixels[pixelIndex] = (byte)((pixels[pixelIndex] & ~0x01) | (-(reverse >> writeIndex++) & 0x01));
pixelIndex += _fileHeader.BytesPerPixel;
}
}
BackingStream.Position = _fileHeader.BitmapOffset + (position * 8 * _fileHeader.BytesPerPixel);
BackingStream.Write(pixels, 0, pixelCount);
BackingStream.Flush();
}