WordsUtils.cs

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

namespace WavPack
{
class WordsUtils
{
	//////////////////////////////// local macros /////////////////////////////////

	internal static int LIMIT_ONES = 16; // maximum consecutive 1s sent for "div" data

	// these control the time constant "slow_level" which is used for hybrid mode
	// that controls bitrate as a function of residual level (HYBRID_BITRATE).
	internal static int SLS = 8;
	internal static int SLO = ((1 << (SLS - 1)));


	// these control the time constant of the 3 median level breakpoints
	internal static int DIV0 = 128; // 5/7 of samples
	internal static int DIV1 = 64; // 10/49 of samples
	internal static int DIV2 = 32; // 20/343 of samples


	///////////////////////////// local table storage ////////////////////////////

	internal static int[] nbits_table =
		new int[]{
0, 1, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4,     // 0 - 15
5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,     // 16 - 31
6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,     // 32 - 47
6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,     // 48 - 63
7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,     // 64 - 79
7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,     // 80 - 95
7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,     // 96 - 111
7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,     // 112 - 127
8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,     // 128 - 143
8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,     // 144 - 159
8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,     // 160 - 175
8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,     // 176 - 191
8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,     // 192 - 207
8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,     // 208 - 223
8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,     // 224 - 239
8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8      // 240 - 255
	};

	internal static int[] log2_table = new int[] { 0x00, 0x01, 0x03, 0x04, 0x06, 0x07, 0x09, 0x0a, 0x0b, 0x0d, 0x0e, 0x10, 0x11, 0x12, 0x14, 0x15, 0x16, 0x18, 0x19, 0x1a, 0x1c, 0x1d, 0x1e, 0x20, 0x21, 0x22, 0x24, 0x25, 0x26, 0x28, 0x29, 0x2a, 0x2c, 0x2d, 0x2e, 0x2f, 0x31, 0x32, 0x33, 0x34, 0x36, 0x37, 0x38, 0x39, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f, 0x41, 0x42, 0x43, 0x44, 0x45, 0x47, 0x48, 0x49, 0x4a, 0x4b, 0x4d, 0x4e, 0x4f, 0x50, 0x51, 0x52, 0x54, 0x55, 0x56, 0x57, 0x58, 0x59, 0x5a, 0x5c, 0x5d, 0x5e, 0x5f, 0x60, 0x61, 0x62, 0x63, 0x64, 0x66, 0x67, 0x68, 0x69, 0x6a, 0x6b, 0x6c, 0x6d, 0x6e, 0x6f, 0x70, 0x71, 0x72, 0x74, 0x75, 0x76, 0x77, 0x78, 0x79, 0x7a, 0x7b, 0x7c, 0x7d, 0x7e, 0x7f, 0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87, 0x88, 0x89, 0x8a, 0x8b, 0x8c, 0x8d, 0x8e, 0x8f, 0x90, 0x91, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97, 0x98, 0x99, 0x9a, 0x9b, 0x9b, 0x9c, 0x9d, 0x9e, 0x9f, 0xa0, 0xa1, 0xa2, 0xa3, 0xa4, 0xa5, 0xa6, 0xa7, 0xa8, 0xa9, 0xa9, 0xaa, 0xab, 0xac, 0xad, 0xae, 0xaf, 0xb0, 0xb1, 0xb2, 0xb2, 0xb3, 0xb4, 0xb5, 0xb6, 0xb7, 0xb8, 0xb9, 0xb9, 0xba, 0xbb, 0xbc, 0xbd, 0xbe, 0xbf, 0xc0, 0xc0, 0xc1, 0xc2, 0xc3, 0xc4, 0xc5, 0xc6, 0xc6, 0xc7, 0xc8, 0xc9, 0xca, 0xcb, 0xcb, 0xcc, 0xcd, 0xce, 0xcf, 0xd0, 0xd0, 0xd1, 0xd2, 0xd3, 0xd4, 0xd4, 0xd5, 0xd6, 0xd7, 0xd8, 0xd8, 0xd9, 0xda, 0xdb, 0xdc, 0xdc, 0xdd, 0xde, 0xdf, 0xe0, 0xe0, 0xe1, 0xe2, 0xe3, 0xe4, 0xe4, 0xe5, 0xe6, 0xe7, 0xe7, 0xe8, 0xe9, 0xea, 0xea, 0xeb, 0xec, 0xed, 0xee, 0xee, 0xef, 0xf0, 0xf1, 0xf1, 0xf2, 0xf3, 0xf4, 0xf4, 0xf5, 0xf6, 0xf7, 0xf7, 0xf8, 0xf9, 0xf9, 0xfa, 0xfb, 0xfc, 0xfc, 0xfd, 0xfe, 0xff, 0xff };

	internal static int[] exp2_table = new int[] { 0x00, 0x01, 0x01, 0x02, 0x03, 0x03, 0x04, 0x05, 0x06, 0x06, 0x07, 0x08, 0x08, 0x09, 0x0a, 0x0b, 0x0b, 0x0c, 0x0d, 0x0e, 0x0e, 0x0f, 0x10, 0x10, 0x11, 0x12, 0x13, 0x13, 0x14, 0x15, 0x16, 0x16, 0x17, 0x18, 0x19, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1d, 0x1e, 0x1f, 0x20, 0x20, 0x21, 0x22, 0x23, 0x24, 0x24, 0x25, 0x26, 0x27, 0x28, 0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2c, 0x2d, 0x2e, 0x2f, 0x30, 0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3a, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f, 0x40, 0x41, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, 0x48, 0x49, 0x4a, 0x4b, 0x4c, 0x4d, 0x4e, 0x4f, 0x50, 0x51, 0x51, 0x52, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58, 0x59, 0x5a, 0x5b, 0x5c, 0x5d, 0x5e, 0x5e, 0x5f, 0x60, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69, 0x6a, 0x6b, 0x6c, 0x6d, 0x6e, 0x6f, 0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78, 0x79, 0x7a, 0x7b, 0x7c, 0x7d, 0x7e, 0x7f, 0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x87, 0x88, 0x89, 0x8a, 0x8b, 0x8c, 0x8d, 0x8e, 0x8f, 0x90, 0x91, 0x92, 0x93, 0x95, 0x96, 0x97, 0x98, 0x99, 0x9a, 0x9b, 0x9c, 0x9d, 0x9f, 0xa0, 0xa1, 0xa2, 0xa3, 0xa4, 0xa5, 0xa6, 0xa8, 0xa9, 0xaa, 0xab, 0xac, 0xad, 0xaf, 0xb0, 0xb1, 0xb2, 0xb3, 0xb4, 0xb6, 0xb7, 0xb8, 0xb9, 0xba, 0xbc, 0xbd, 0xbe, 0xbf, 0xc0, 0xc2, 0xc3, 0xc4, 0xc5, 0xc6, 0xc8, 0xc9, 0xca, 0xcb, 0xcd, 0xce, 0xcf, 0xd0, 0xd2, 0xd3, 0xd4, 0xd6, 0xd7, 0xd8, 0xd9, 0xdb, 0xdc, 0xdd, 0xde, 0xe0, 0xe1, 0xe2, 0xe4, 0xe5, 0xe6, 0xe8, 0xe9, 0xea, 0xec, 0xed, 0xee, 0xf0, 0xf1, 0xf2, 0xf4, 0xf5, 0xf6, 0xf8, 0xf9, 0xfa, 0xfc, 0xfd, 0xff };

	internal static int[] ones_count_table = new int[] {
0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,4,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,5,
0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,4,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,6,
0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,4,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,5,
0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,4,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,7,
0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,4,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,5,
0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,4,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,6,
0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,4,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,5,
0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,4,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0,8
};

	///////////////////////////// executable code ////////////////////////////////


	// Read the median log2 values from the specifed metadata structure, convert
	// them back to 32-bit unsigned values and store them. If length is not
	// exactly correct then we flag and return an error.

	internal static int read_entropy_vars(WavpackStream wps, WavpackMetadata wpmd)
	{
		byte[] byteptr = wpmd.data;
		int[] b_array = new int[12];
		int i = 0;
		words_data w = new words_data();

		for (i = 0; i < 6; i++)
		{
			b_array[i] = byteptr[i];
		}

		w.holding_one = false;
		w.holding_zero = false;

		if (wpmd.byte_length != 12)
		{
			if ((wps.wphdr.flags & (Defines.MONO_FLAG | Defines.FALSE_STEREO)) == 0)
			{
				return Defines.FALSE;
			}
		}

		w.c[0].median[0] = exp2s(b_array[0] + (b_array[1] << 8));
		w.c[0].median[1] = exp2s(b_array[2] + (b_array[3] << 8));
		w.c[0].median[2] = exp2s(b_array[4] + (b_array[5] << 8));

		if ((wps.wphdr.flags & (Defines.MONO_FLAG | Defines.FALSE_STEREO)) == 0)
		{
			for (i = 6; i < 12; i++)
			{
				b_array[i] = byteptr[i];
			}
			w.c[1].median[0] = exp2s(b_array[6] + (b_array[7] << 8));
			w.c[1].median[1] = exp2s(b_array[8] + (b_array[9] << 8));
			w.c[1].median[2] = exp2s(b_array[10] + (b_array[11] << 8));
		}

		wps.w = w;

		return Defines.TRUE;
	}


	// Read the hybrid related values from the specifed metadata structure, convert
	// them back to their internal formats and store them. The extended profile
	// stuff is not implemented yet, so return an error if we get more data than
	// we know what to do with.

	internal static int read_hybrid_profile(WavpackStream wps, WavpackMetadata wpmd)
	{
		byte[] byteptr = wpmd.data;
		int bytecnt = wpmd.byte_length;
		int buffer_counter = 0;
		int uns_buf = 0;
		int uns_buf_plusone = 0;

		if ((wps.wphdr.flags & Defines.HYBRID_BITRATE) != 0)
		{
			uns_buf = byteptr[buffer_counter];
			uns_buf_plusone = byteptr[buffer_counter + 1];

			wps.w.c[0].slow_level = exp2s(uns_buf + (uns_buf_plusone << 8));
			buffer_counter = buffer_counter + 2;

			if ((wps.wphdr.flags & (Defines.MONO_FLAG | Defines.FALSE_STEREO)) == 0)
			{
				uns_buf = byteptr[buffer_counter];
				uns_buf_plusone = byteptr[buffer_counter + 1];
				wps.w.c[1].slow_level = exp2s(uns_buf + (uns_buf_plusone << 8));
				buffer_counter = buffer_counter + 2;
			}
		}

		uns_buf = byteptr[buffer_counter];
		uns_buf_plusone = byteptr[buffer_counter + 1];

		wps.w.bitrate_acc[0] = (uns_buf + (uns_buf_plusone << 8)) << 16;
		buffer_counter = buffer_counter + 2;

		if ((wps.wphdr.flags & (Defines.MONO_FLAG | Defines.FALSE_STEREO)) == 0)
		{
			uns_buf = byteptr[buffer_counter];
			uns_buf_plusone = byteptr[buffer_counter + 1];

			wps.w.bitrate_acc[1] = (uns_buf + (uns_buf_plusone << 8)) << 16;
			buffer_counter = buffer_counter + 2;
		}

		if (buffer_counter < bytecnt)
		{
			uns_buf = byteptr[buffer_counter];
			uns_buf_plusone = byteptr[buffer_counter + 1];

			wps.w.bitrate_delta[0] = exp2s((short)(uns_buf + (uns_buf_plusone << 8)));
			buffer_counter = buffer_counter + 2;

			if ((wps.wphdr.flags & (Defines.MONO_FLAG | Defines.FALSE_STEREO)) == 0)
			{
				uns_buf = byteptr[buffer_counter];
				uns_buf_plusone = byteptr[buffer_counter + 1];
				wps.w.bitrate_delta[1] = exp2s((short)(uns_buf + (uns_buf_plusone << 8)));
				buffer_counter = buffer_counter + 2;
			}

			if (buffer_counter < bytecnt)
				return Defines.FALSE;
		}
		else
			wps.w.bitrate_delta[0] = wps.w.bitrate_delta[1] = 0;

		return Defines.TRUE;
	}

	// This function is called during both encoding and decoding of hybrid data to
	// update the "error_limit" variable which determines the maximum sample error
	// allowed in the main bitstream. In the HYBRID_BITRATE mode (which is the only
	// currently implemented) this is calculated from the slow_level values and the
	// bitrate accumulators. Note that the bitrate accumulators can be changing.

	internal static words_data update_error_limit(words_data w, long flags)
	{
		int bitrate_0 = (int)((w.bitrate_acc[0] += w.bitrate_delta[0]) >> 16);

		if ((flags & (Defines.MONO_FLAG | Defines.FALSE_STEREO)) != 0)
		{
			if ((flags & Defines.HYBRID_BITRATE) != 0)
			{
				int slow_log_0 = (int)((w.c[0].slow_level + SLO) >> SLS);

				if (slow_log_0 - bitrate_0 > -0x100)
					w.c[0].error_limit = exp2s(slow_log_0 - bitrate_0 + 0x100);
				else
					w.c[0].error_limit = 0;
			}
			else
				w.c[0].error_limit = exp2s(bitrate_0);
		}
		else
		{
			int bitrate_1 = (int)((w.bitrate_acc[1] += w.bitrate_delta[1]) >> 16);

			if ((flags & Defines.HYBRID_BITRATE) != 0)
			{
				int slow_log_0 = (int)((w.c[0].slow_level + SLO) >> SLS);
				int slow_log_1 = (int)((w.c[1].slow_level + SLO) >> SLS);

				if ((flags & Defines.HYBRID_BALANCE) != 0)
				{
					int balance = (slow_log_1 - slow_log_0 + bitrate_1 + 1) >> 1;

					if (balance > bitrate_0)
					{
						bitrate_1 = bitrate_0 * 2;
						bitrate_0 = 0;
					}
					else if (-balance > bitrate_0)
					{
						bitrate_0 = bitrate_0 * 2;
						bitrate_1 = 0;
					}
					else
					{
						bitrate_1 = bitrate_0 + balance;
						bitrate_0 = bitrate_0 - balance;
					}
				}

				if (slow_log_0 - bitrate_0 > -0x100)
					w.c[0].error_limit = exp2s(slow_log_0 - bitrate_0 + 0x100);
				else
					w.c[0].error_limit = 0;

				if (slow_log_1 - bitrate_1 > -0x100)
					w.c[1].error_limit = exp2s(slow_log_1 - bitrate_1 + 0x100);
				else
					w.c[1].error_limit = 0;
			}
			else
			{
				w.c[0].error_limit = exp2s(bitrate_0);
				w.c[1].error_limit = exp2s(bitrate_1);
			}
		}

		return w;
	}


	// Read the next word from the bitstream "wvbits" and return the value. This
	// function can be used for hybrid or lossless streams, but since an
	// optimized version is available for lossless this function would normally
	// be used for hybrid only. If a hybrid lossless stream is being read then
	// the "correction" offset is written at the specified pointer. A return value
	// of WORD_EOF indicates that the end of the bitstream was reached (all 1s) or
	// some other error occurred.

	internal static int get_words(long nsamples, long flags, words_data w, Bitstream bs, int[] buffer, int bufferStartPos)
	{
		entropy_data[] c = w.c;
		int csamples;
		int buffer_counter = bufferStartPos;
		int entidx = 1;

		if ((flags & (Defines.MONO_FLAG | Defines.FALSE_STEREO)) == 0)
		// if not mono
		{
			nsamples *= 2;
		}
		else
		{
			// it is mono
			entidx = 0;
		}

		for (csamples = 0; csamples < nsamples; ++csamples)
		{
			int ones_count;
			long low, high, mid;

			if ((flags & (Defines.MONO_FLAG | Defines.FALSE_STEREO)) == 0)
			// if not mono
			{
				if (entidx == 1)
					entidx = 0;
				else
					entidx = 1;
			}

			if ((w.c[0].median[0] & ~1) == 0 && !w.holding_zero && !w.holding_one && (w.c[1].median[0] & ~1) == 0)
			{
				long mask;
				int cbits;

				if (w.zeros_acc > 0)
				{
					if (--w.zeros_acc > 0)
					{
						c[entidx].slow_level -= (c[entidx].slow_level + SLO) >> SLS;
						buffer[buffer_counter] = 0;
						buffer_counter++;
						continue;
					}
				}
				else
				{
					for (cbits = 0; cbits < 33 && BitsUtils.getbit(bs); ++cbits) ;

					if (cbits == 33)
						break;

					if (cbits < 2)
						w.zeros_acc = cbits;
					else
					{
						for (mask = 1, w.zeros_acc = 0; --cbits > 0; mask <<= 1)
							if (BitsUtils.getbit(bs))
								w.zeros_acc |= mask;

						w.zeros_acc |= mask;
					}

					if (w.zeros_acc > 0)
					{
						c[entidx].slow_level -= ((c[entidx].slow_level + SLO) >> SLS);
						w.c[0].median[0] = 0;
						w.c[0].median[1] = 0;
						w.c[0].median[2] = 0;
						w.c[1].median[0] = 0;
						w.c[1].median[1] = 0;
						w.c[1].median[2] = 0;

						buffer[buffer_counter] = 0;
						buffer_counter++;
						continue;
					}
				}
			}

			if (w.holding_zero)
			{
				w.holding_zero = false;
				ones_count = 0;
			}
			else
			{
				if (bs.bc < 8)
				{
					bs.ptr++;
					bs.buf_index++;

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

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

					bs.bc += 8;
				}

				byte next8 = (byte)bs.sr;

				if (next8 == 0xff)
				{
					bs.bc -= 8;
					bs.sr >>= 8;

					for (ones_count = 8; ones_count < (LIMIT_ONES + 1) && BitsUtils.getbit(bs); ++ones_count) ;

					if (ones_count == (LIMIT_ONES + 1))
						break;

					if (ones_count == LIMIT_ONES)
					{
						int mask;
						int cbits;

						for (cbits = 0; cbits < 33 && BitsUtils.getbit(bs); ++cbits) ;

						if (cbits == 33)
							break;

						if (cbits < 2)
							ones_count = cbits;
						else
						{
							for (mask = 1, ones_count = 0; --cbits > 0; mask <<= 1)
								if (BitsUtils.getbit(bs))
									ones_count |= mask;

							ones_count |= mask;
						}

						ones_count += LIMIT_ONES;
					}
				}
				else
				{
					bs.bc -= (ones_count = ones_count_table[next8]) + 1;
					bs.sr >>= ones_count + 1; // needs to be unsigned
				}

				if (w.holding_one)
				{
					w.holding_one = (ones_count & 1) > 0;
					ones_count = (ones_count >> 1) + 1;
				}
				else
				{
					w.holding_one = (ones_count & 1) > 0;
					ones_count >>= 1;
				}

				w.holding_zero = !w.holding_one;
			}

			if ((flags & Defines.HYBRID_FLAG) > 0 && ((flags & (Defines.MONO_FLAG | Defines.FALSE_STEREO)) > 0 || (csamples & 1) == 0))
				w = update_error_limit(w, flags);

			if (ones_count == 0)
			{
				low = 0;
				high = (((c[entidx].median[0]) >> 4) + 1) - 1;

				// for c# I replace the division by DIV0 with >> 7
				c[entidx].median[0] -= (((c[entidx].median[0] + (DIV0 - 2)) >> 7) * 2);
			}
			else
			{
				low = (((c[entidx].median[0]) >> 4) + 1);

				// for c# I replace the division by DIV0 with >> 7
				c[entidx].median[0] += ((c[entidx].median[0] + DIV0) >> 7) * 5;

				if (ones_count == 1)
				{

					high = low + (((c[entidx].median[1]) >> 4) + 1) - 1;
					// for c# I replace the division by DIV1 with >> 6
					c[entidx].median[1] -= ((c[entidx].median[1] + (DIV1 - 2)) >> 6) * 2;
				}
				else
				{
					low += (((c[entidx].median[1]) >> 4) + 1);
					// for c# I replace the division by DIV1 with >> 6
					c[entidx].median[1] += ((c[entidx].median[1] + DIV1) >> 6) * 5;

					if (ones_count == 2)
					{
						high = low + (((c[entidx].median[2]) >> 4) + 1) - 1;
						// for c# I replace the division by DIV2 with >> 5
						c[entidx].median[2] -= ((c[entidx].median[2] + (DIV2 - 2)) >> 5) * 2;
					}
					else
					{
						low += (ones_count - 2) * (((c[entidx].median[2]) >> 4) + 1);
						high = low + (((c[entidx].median[2]) >> 4) + 1) - 1;
						// for c# I replace the division by DIV2 with >> 5
						c[entidx].median[2] += ((c[entidx].median[2] + DIV2) >> 5) * 5;
					}
				}
			}

			mid = (high + low + 1) >> 1;

			if (c[entidx].error_limit == 0)
			{
				mid = read_code(bs, high - low);

				mid = mid + low;
			}
			else
				while (high - low > c[entidx].error_limit)
				{
					if (BitsUtils.getbit(bs))
						mid = (high + (low = mid) + 1) >> 1;
					else
						mid = ((high = mid - 1) + low + 1) >> 1;
				}

			if (BitsUtils.getbit(bs))
				buffer[buffer_counter] = (int)~mid;
			else
				buffer[buffer_counter] = (int)mid;

			buffer_counter++;

			if ((flags & Defines.HYBRID_BITRATE) > 0)
				c[entidx].slow_level = c[entidx].slow_level - ((c[entidx].slow_level + SLO) >> SLS) + mylog2(mid);
		}

		w.c = c;

		if ((flags & (Defines.MONO_FLAG | Defines.FALSE_STEREO)) != 0)
			return csamples;
		else
			return (csamples / 2);
	}

	internal static int count_bits(long av)
	{
		if (av < 256)   // 1 << 8
		{
			return nbits_table[av];
		}
		else
		{
			if (av < 65536) // 1 << 16
			{
				return nbits_table[(av >> 8)] + 8;
			}
			else
			{
				if (av < 16777216)  // 1 << 24
				{
					return nbits_table[(av >> 16)] + 16;
				}
				else
				{
					return nbits_table[(av >> 24)] + 24;
				}
			}
		}
	}


	// Read a single unsigned value from the specified bitstream with a value
	// from 0 to maxcode. If there are exactly a power of two number of possible
	// codes then this will read a fixed number of bits; otherwise it reads the
	// minimum number of bits and then determines whether another bit is needed
	// to define the code.

	internal static long read_code(Bitstream bs, long maxcode)
	{
		int bitcount = count_bits(maxcode);
		long extras = (1 << bitcount) - maxcode - 1;
		long code;

		if (bitcount == 0)
		{
			return (0);
		}

		code = BitsUtils.getbits(bitcount - 1, bs);

		code &= (1 << (bitcount - 1)) - 1;

		if (code >= extras)
		{
			code = (code << 1) - extras;

			if (BitsUtils.getbit(bs))
				++code;
		}

		return (code);
	}


	// The concept of a base 2 logarithm is used in many parts of WavPack. It is
	// a way of sufficiently accurately representing 32-bit signed and unsigned
	// values storing only 16 bits (actually fewer). It is also used in the hybrid
	// mode for quickly comparing the relative magnitude of large values (i.e.
	// division) and providing smooth exponentials using only addition.

	// These are not strict logarithms in that they become linear around zero and
	// can therefore represent both zero and negative values. They have 8 bits
	// of precision and in "roundtrip" conversions the total error never exceeds 1
	// part in 225 except for the cases of +/-115 and +/-195 (which error by 1).


	// This function returns the log2 for the specified 32-bit unsigned value.
	// The maximum value allowed is about 0xff800000 and returns 8447.

	internal static int mylog2(long avalue)
	{
		int dbits;

		if ((avalue += (avalue >> 9)) < (1 << 8))
		{
			dbits = nbits_table[(int)avalue];
			return (dbits << 8) + log2_table[(int)(avalue << (9 - dbits)) & 0xff];
		}
		else
		{
			if (avalue < (1L << 16))
				dbits = nbits_table[(int)(avalue >> 8)] + 8;
			else if (avalue < (1L << 24))
				dbits = nbits_table[(int)(avalue >> 16)] + 16;
			else
				dbits = nbits_table[(int)(avalue >> 24)] + 24;

			return (dbits << 8) + log2_table[(int)(avalue >> (dbits - 9)) & 0xff];
		}
	}


	// This function returns the log2 for the specified 32-bit signed value.
	// All input values are valid and the return values are in the range of
	// +/- 8192.

	internal virtual int log2s(int value_Renamed)
	{
		if (value_Renamed < 0)
		{
			return -mylog2(-value_Renamed);
		}
		else
		{
			return mylog2(value_Renamed);
		}
	}


	// This function returns the original integer represented by the supplied
	// logarithm (at least within the provided accuracy). The log is signed,
	// but since a full 32-bit value is returned this can be used for unsigned
	// conversions as well (i.e. the input range is -8192 to +8447).

	internal static int exp2s(int log)
	{
		long value_Renamed;

		if (log < 0)
			return -exp2s(-log);

		value_Renamed = exp2_table[log & 0xff] | 0x100;

		if ((log >>= 8) <= 9)
			return ((int)(value_Renamed >> (9 - log)));
		else
			return ((int)(value_Renamed << (log - 9)));
	}


	// These two functions convert internal weights (which are normally +/-1024)
	// to and from an 8-bit signed character version for storage in metadata. The
	// weights are clipped here in the case that they are outside that range.

	internal static int restore_weight(sbyte weight)
	{
		int result;

		if ((result = weight << 3) > 0)
			result += (result + 64) >> 7;

		return result;
	}
}
}