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More code cleanup after decoding optimization
This commit is contained in:
Grigory Chudov
@@ -1,42 +1,159 @@
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using System;
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namespace CUETools.Codecs
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{
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public class Crc16
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public static class Crc16
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{
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ushort[] table = new ushort[256];
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const int GF2_DIM = 16;
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public static ushort[] table = new ushort[256];
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private static readonly ushort[,] combineTable = new ushort[GF2_DIM, GF2_DIM];
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private static readonly ushort[,] substractTable = new ushort[GF2_DIM, GF2_DIM];
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public unsafe ushort ComputeChecksum(byte[] bytes, int pos, int count)
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public static unsafe ushort ComputeChecksum(ushort crc, byte[] bytes, int pos, int count)
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{
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fixed (byte* bs = bytes)
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return ComputeChecksum(bs + pos, count);
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return ComputeChecksum(crc, bs + pos, count);
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}
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public unsafe ushort ComputeChecksum(byte* bytes, int count)
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public static unsafe ushort ComputeChecksum(ushort crc, byte* bytes, int count)
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{
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ushort crc = 0;
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fixed (ushort* t = table)
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for (int i = count; i > 0; i--)
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crc = (ushort)((crc << 8) ^ t[(crc >> 8) ^ *(bytes++)]);
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return crc;
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}
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public Crc16()
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const ushort polynomial = 0x8005;
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const ushort reversePolynomial = 0xa001;
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const ushort reversePolynomial2 = 0x4003;
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static unsafe Crc16()
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{
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int bits = 16;
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int poly16 = 0x8005;
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int poly = (poly16 + (1 << bits));
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for (ushort i = 0; i < table.Length; i++)
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{
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int crc = i;
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for (int j = 0; j < bits; j++)
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{
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if ((crc & (1U << (bits - 1))) != 0)
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crc = ((crc << 1) ^ poly);
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else
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crc <<= 1;
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}
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//table[i] = (crc & ((1<<bits)-1));
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table[i] = (ushort)(crc & 0xffff);
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}
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}
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}
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int poly = (polynomial + (1 << GF2_DIM));
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for (ushort i = 0; i < table.Length; i++)
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{
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int crc = i;
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for (int j = 0; j < GF2_DIM; j++)
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{
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if ((crc & (1U << (GF2_DIM - 1))) != 0)
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crc = ((crc << 1) ^ poly);
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else
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crc <<= 1;
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}
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table[i] = (ushort)(crc & ((1 << GF2_DIM) - 1));
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}
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combineTable[0, 0] = reversePolynomial;
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substractTable[0, GF2_DIM - 1] = reversePolynomial2;
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for (int n = 1; n < GF2_DIM; n++)
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{
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combineTable[0, n] = (ushort)(1 << (n - 1));
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substractTable[0, n - 1] = (ushort)(1 << n);
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}
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fixed (ushort* ct = &combineTable[0, 0], st = &substractTable[0, 0])
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{
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//for (int i = 0; i < GF2_DIM; i++)
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// st[32 + i] = ct[i];
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//invert_binary_matrix(st + 32, st, GF2_DIM);
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for (int i = 1; i < GF2_DIM; i++)
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{
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gf2_matrix_square(ct + i * GF2_DIM, ct + (i - 1) * GF2_DIM);
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gf2_matrix_square(st + i * GF2_DIM, st + (i - 1) * GF2_DIM);
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}
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}
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}
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private static unsafe ushort gf2_matrix_times(ushort* mat, ushort uvec)
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{
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int vec = ((int) uvec) << 16;
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return (ushort)(
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(*(mat++) & ((vec << 15) >> 31)) ^
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(*(mat++) & ((vec << 14) >> 31)) ^
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(*(mat++) & ((vec << 13) >> 31)) ^
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(*(mat++) & ((vec << 12) >> 31)) ^
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(*(mat++) & ((vec << 11) >> 31)) ^
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(*(mat++) & ((vec << 10) >> 31)) ^
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(*(mat++) & ((vec << 09) >> 31)) ^
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(*(mat++) & ((vec << 08) >> 31)) ^
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(*(mat++) & ((vec << 07) >> 31)) ^
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(*(mat++) & ((vec << 06) >> 31)) ^
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(*(mat++) & ((vec << 05) >> 31)) ^
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(*(mat++) & ((vec << 04) >> 31)) ^
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(*(mat++) & ((vec << 03) >> 31)) ^
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(*(mat++) & ((vec << 02) >> 31)) ^
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(*(mat++) & ((vec << 01) >> 31)) ^
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(*(mat++) & (vec >> 31)));
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}
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private static unsafe void gf2_matrix_square(ushort* square, ushort* mat)
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{
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for (int n = 0; n < GF2_DIM; n++)
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square[n] = gf2_matrix_times(mat, mat[n]);
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}
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public static unsafe ushort Combine(ushort crc1, ushort crc2, long len2)
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{
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crc1 = (ushort)Crc32.Reflect(crc1, 16);
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crc2 = (ushort)Crc32.Reflect(crc2, 16);
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/* degenerate case */
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if (len2 == 0)
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return crc1;
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if (crc1 == 0)
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return crc2;
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if (len2 < 0)
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throw new ArgumentException("crc.Combine length cannot be negative", "len2");
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fixed (ushort* ct = &combineTable[0, 0])
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{
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int n = 3;
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do
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{
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/* apply zeros operator for this bit of len2 */
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if ((len2 & 1) != 0)
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crc1 = gf2_matrix_times(ct + GF2_DIM * n, crc1);
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len2 >>= 1;
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n = (n + 1) & (GF2_DIM - 1);
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/* if no more bits set, then done */
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} while (len2 != 0);
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}
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/* return combined crc */
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crc1 ^= crc2;
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crc1 = (ushort)Crc32.Reflect(crc1, 16);
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return crc1;
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}
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public static unsafe ushort Substract(ushort crc1, ushort crc2, long len2)
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{
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crc1 = (ushort)Crc32.Reflect(crc1, 16);
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crc2 = (ushort)Crc32.Reflect(crc2, 16);
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/* degenerate case */
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if (len2 == 0)
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return crc1;
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if (len2 < 0)
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throw new ArgumentException("crc.Combine length cannot be negative", "len2");
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crc1 ^= crc2;
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fixed (ushort* st = &substractTable[0, 0])
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{
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int n = 3;
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do
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{
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/* apply zeros operator for this bit of len2 */
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if ((len2 & 1) != 0)
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crc1 = gf2_matrix_times(st + GF2_DIM * n, crc1);
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len2 >>= 1;
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n = (n + 1) & (GF2_DIM - 1);
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/* if no more bits set, then done */
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} while (len2 != 0);
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}
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/* return combined crc */
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crc1 = (ushort)Crc32.Reflect(crc1, 16);
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return crc1;
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}
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}
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}
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