/// <summary>
/// Reads the size of a segment at the current position.
/// </summary>
/// <returns>
/// A <see cref="System.UInt16"/> with the size of the current segment.
/// </returns>
private ushort ReadSegmentSize()
{
long position = Tell;
ByteVector segment_size_bytes = ReadBlock(2);
if (segment_size_bytes.Count != 2)
{
throw new CorruptFileException("Could not read enough bytes to determine segment size");
}
ushort segment_size = segment_size_bytes.ToUShort();
// the size itself must be contained in the segment size
// so the smallest (theoretically) possible number of bytes if 2
if (segment_size < 2)
{
throw new CorruptFileException(String.Format("Invalid segment size ({0} bytes)", segment_size));
}
long length = 0;
try {
length = Length;
} catch (Exception) {
// Probably not supported by stream.
}
if (length > 0 && position + segment_size >= length)
{
throw new CorruptFileException("Segment size exceeds file size");
}
return(segment_size);
}
private ushort ReadSegmentSize()
{
long position = Tell;
ByteVector segment_size_bytes = ReadBlock(2);
if (segment_size_bytes.Count != 2)
{
throw new CorruptFileException("Could not read enough bytes to determine segment size");
}
ushort segment_size = segment_size_bytes.ToUShort();
if (segment_size < 2)
{
throw new CorruptFileException(String.Format("Invalid segment size ({0} bytes)", segment_size));
}
long length = 0;
try
{
length = Length;
}
catch (Exception)
{
}
if (length > 0 && position + segment_size >= length)
{
throw new CorruptFileException("Segment size exceeds file size");
}
return(segment_size);
}
/// <summary>
/// Validates if the opened file is actually a JPEG.
/// </summary>
private void ValidateHeader()
{
ByteVector segment = ReadBlock(2);
if (segment.ToUShort() != 0xFFD8)
{
throw new CorruptFileException("Expected SOI marker at the start of the file.");
}
}
