BitsUtils.cs

/*
** BitsUtils.cs
**
** Copyright (c) 2010-2016 Peter McQuillan
**
** All Rights Reserved.
**                       
** Distributed under the BSD Software License (see license.txt)  
***/

namespace WavPack
{
class BitsUtils
{
	internal static bool getbit(Bitstream bs)
	{
		if (bs.bc > 0)
			bs.bc--;
		else
		{
			bs.ptr++;
			bs.buf_index++;
			bs.bc = 7;

			if (bs.ptr == bs.end)
				// wrap call here
				bs = bs_read(bs);

			bs.sr = bs.buf[bs.buf_index];
		}

		bool result = (bs.sr & 1) > 0;
		bs.sr >>= 1;
		return result;
	}

	internal static long getbits(int nbits, Bitstream bs)
	{
		long retval;

		while (nbits > bs.bc)
		{
			bs.ptr++;
			bs.buf_index++;

			if (bs.ptr == bs.end)
				bs = bs_read(bs);

			bs.sr |= (uint)(bs.buf[bs.buf_index] << bs.bc);

			bs.bc += 8;
		}

		retval = bs.sr;

		if (bs.bc > 32)
		{
			bs.bc -= nbits;
			bs.sr = (uint)(bs.buf[bs.buf_index] >> (8 - bs.bc));
		}
		else
		{
			bs.bc -= nbits;
			bs.sr >>= nbits;
		}

		return retval;
	}

	internal static Bitstream bs_open_read(byte[] stream, int buffer_start, int buffer_end, System.IO.BinaryReader file, int file_bytes, int passed)
	{
		Bitstream bs = new Bitstream();

		bs.buf = stream;
		bs.buf_index = buffer_start;
		bs.end = buffer_end;
		bs.sr = 0;
		bs.bc = 0;

		if (passed != 0)
		{
			bs.ptr = (short)(bs.end - 1);
			bs.file_bytes = file_bytes;
			bs.file = file;
		}
		else
		{
			bs.buf_index--;
			bs.ptr = -1;
		}

		return bs;
	}

	internal static Bitstream bs_read(Bitstream bs)
	{
		if (bs.file_bytes > 0)
		{
			int bytes_read;

			var bytes_to_read = bs.buf.Length;

			if (bytes_to_read > bs.file_bytes)
				bytes_to_read = bs.file_bytes;

			try
			{
				bytes_read = bs.file.BaseStream.Read(bs.buf, 0, bytes_to_read);

				bs.buf_index = 0;
			}
			catch (System.Exception e)
			{
				System.Console.Error.WriteLine("Big error while reading file: " + e);
				bytes_read = 0;
			}

			if (bytes_read > 0)
			{
				bs.end = (short)(bytes_read);
				bs.file_bytes -= bytes_read;
			}
			else
			{
				for (int i = 0; i < bs.buf.Length; i++)
				{
					bs.buf[i] = unchecked((byte)-1);
				}
				bs.error = 1;
			}
		}
		else
		{
			bs.error = 1;

			for (int i = 0; i < bs.buf.Length; i++)
			{
				bs.buf[i] = unchecked((byte)-1);
			}
		}

		bs.ptr = 0;
		bs.buf_index = 0;

		return bs;
	}
}
}