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302 lines
10 KiB
C#
302 lines
10 KiB
C#
//! \file Checksum.cs
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//! \date Sun Apr 24 18:09:11 2016
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//! \brief Various checksum algorithms implementations.
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//
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// Copyright (C) 2014-2016 by morkt
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//
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// Permission is hereby granted, free of charge, to any person obtaining a copy
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// of this software and associated documentation files (the "Software"), to
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// deal in the Software without restriction, including without limitation the
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// rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
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// sell copies of the Software, and to permit persons to whom the Software is
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// furnished to do so, subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be included in
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// all copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
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// IN THE SOFTWARE.
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//
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using System.IO;
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namespace GameRes.Utility
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{
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public interface ICheckSum
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{
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uint Value { get; }
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void Update (byte[] buf, int pos, int len);
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}
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public sealed class Crc32 : ICheckSum
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{
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/* Table of CRCs of all 8-bit messages. */
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private static readonly uint[] crc_table = InitializeTable();
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public static uint[] Table { get { return crc_table; } }
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/* Make the table for a fast CRC. */
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private static uint[] InitializeTable ()
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{
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uint[] table = new uint[256];
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for (uint n = 0; n < 256; n++)
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{
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uint c = n;
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for (int k = 0; k < 8; k++)
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{
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if (0 != (c & 1))
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c = 0xedb88320 ^ (c >> 1);
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else
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c = c >> 1;
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}
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table[n] = c;
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}
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return table;
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}
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/* Update a running CRC with the bytes buf[0..len-1]--the CRC
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should be initialized to all 1's, and the transmitted value
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is the 1's complement of the final running CRC (see the
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crc() routine below)). */
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public static uint UpdateCrc (uint crc, byte[] buf, int pos, int len)
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{
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uint c = crc;
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for (int n = 0; n < len; n++)
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c = crc_table[(c ^ buf[pos+n]) & 0xff] ^ (c >> 8);
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return c;
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}
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/* Return the CRC of the bytes buf[0..len-1]. */
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public static uint Compute (byte[] buf, int pos, int len)
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{
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return UpdateCrc (0xffffffff, buf, pos, len) ^ 0xffffffff;
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}
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private uint m_crc = 0xffffffff;
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public uint Value { get { return m_crc^0xffffffff; } }
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public void Update (byte[] buf, int pos, int len)
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{
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m_crc = UpdateCrc (m_crc, buf, pos, len);
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}
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}
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/* Adler32 implementation -- borrowed from the 'zlib' compression library.
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Copyright (C) 1995-2013 Jean-loup Gailly and Mark Adler
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This software is provided 'as-is', without any express or implied
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warranty. In no event will the authors be held liable for any damages
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arising from the use of this software.
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Permission is granted to anyone to use this software for any purpose,
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including commercial applications, and to alter it and redistribute it
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freely, subject to the following restrictions:
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1. The origin of this software must not be misrepresented; you must not
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claim that you wrote the original software. If you use this software
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in a product, an acknowledgment in the product documentation would be
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appreciated but is not required.
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2. Altered source versions must be plainly marked as such, and must not be
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misrepresented as being the original software.
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3. This notice may not be removed or altered from any source distribution.
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*/
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public sealed class Adler32 : ICheckSum
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{
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const uint BASE = 65521; /* largest prime smaller than 65536 */
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const int NMAX = 5552;
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public static uint Compute (byte[] buf, int pos, int len)
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{
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if (0 == len)
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return 1;
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unsafe
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{
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fixed (byte* ptr = &buf[pos])
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{
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return Update (1, ptr, len);
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}
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}
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}
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public unsafe static uint Compute (byte* buf, int len)
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{
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return Update (1, buf, len);
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}
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private unsafe static uint Update (uint adler, byte* buf, int len)
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{
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/* split Adler-32 into component sums */
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uint sum2 = (adler >> 16) & 0xffff;
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adler &= 0xffff;
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/* in case user likes doing a byte at a time, keep it fast */
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if (1 == len) {
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adler += *buf;
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if (adler >= BASE)
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adler -= BASE;
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sum2 += adler;
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if (sum2 >= BASE)
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sum2 -= BASE;
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return adler | (sum2 << 16);
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}
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/* in case short lengths are provided, keep it somewhat fast */
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if (len < 16) {
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while (0 != len--) {
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adler += *buf++;
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sum2 += adler;
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}
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if (adler >= BASE)
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adler -= BASE;
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sum2 %= BASE; /* only added so many BASE's */
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return adler | (sum2 << 16);
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}
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/* do length NMAX blocks -- requires just one modulo operation */
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while (len >= NMAX) {
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len -= NMAX;
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int n = NMAX / 16; /* NMAX is divisible by 16 */
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do {
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/* 16 sums unrolled */
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adler += buf[0]; sum2 += adler;
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adler += buf[1]; sum2 += adler;
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adler += buf[2]; sum2 += adler;
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adler += buf[3]; sum2 += adler;
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adler += buf[4]; sum2 += adler;
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adler += buf[5]; sum2 += adler;
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adler += buf[6]; sum2 += adler;
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adler += buf[7]; sum2 += adler;
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adler += buf[8]; sum2 += adler;
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adler += buf[9]; sum2 += adler;
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adler += buf[10]; sum2 += adler;
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adler += buf[11]; sum2 += adler;
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adler += buf[12]; sum2 += adler;
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adler += buf[13]; sum2 += adler;
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adler += buf[14]; sum2 += adler;
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adler += buf[15]; sum2 += adler;
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buf += 16;
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} while (0 != --n);
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adler %= BASE;
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sum2 %= BASE;
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}
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/* do remaining bytes (less than NMAX, still just one modulo) */
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if (0 != len) { /* avoid modulos if none remaining */
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while (len >= 16) {
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len -= 16;
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adler += buf[0]; sum2 += adler;
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adler += buf[1]; sum2 += adler;
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adler += buf[2]; sum2 += adler;
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adler += buf[3]; sum2 += adler;
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adler += buf[4]; sum2 += adler;
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adler += buf[5]; sum2 += adler;
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adler += buf[6]; sum2 += adler;
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adler += buf[7]; sum2 += adler;
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adler += buf[8]; sum2 += adler;
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adler += buf[9]; sum2 += adler;
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adler += buf[10]; sum2 += adler;
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adler += buf[11]; sum2 += adler;
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adler += buf[12]; sum2 += adler;
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adler += buf[13]; sum2 += adler;
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adler += buf[14]; sum2 += adler;
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adler += buf[15]; sum2 += adler;
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buf += 16;
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}
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while (0 != len--) {
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adler += *buf++;
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sum2 += adler;
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}
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adler %= BASE;
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sum2 %= BASE;
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}
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/* return recombined sums */
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return adler | (sum2 << 16);
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}
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private uint m_adler = 1;
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public uint Value { get { return m_adler; } }
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public void Update (byte[] buf, int pos, int len)
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{
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if (0 == len)
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return;
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unsafe
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{
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fixed (byte* ptr = &buf[pos])
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{
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m_adler = Update (m_adler, ptr, len);
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}
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}
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}
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public unsafe uint Update (byte* buf, int len)
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{
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m_adler = Update (m_adler, buf, len);
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return m_adler;
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}
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}
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public class CheckedStream : Stream
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{
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Stream m_stream;
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ICheckSum m_checksum;
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public override bool CanRead { get { return m_stream.CanRead; } }
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public override bool CanWrite { get { return m_stream.CanWrite; } }
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public override bool CanSeek { get { return m_stream.CanSeek; } }
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public override long Length { get { return m_stream.Length; } }
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public Stream BaseStream { get { return m_stream; } }
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public uint CheckSumValue { get { return m_checksum.Value; } }
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public CheckedStream (Stream stream, ICheckSum algorithm)
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{
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m_stream = stream;
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m_checksum = algorithm;
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}
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public override int Read (byte[] buffer, int offset, int count)
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{
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int read = m_stream.Read (buffer, offset, count);
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if (read > 0)
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m_checksum.Update (buffer, offset, read);
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return read;
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}
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public override void Write (byte[] buffer, int offset, int count)
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{
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m_stream.Write (buffer, offset, count);
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m_checksum.Update (buffer, offset, count);
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}
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public override long Position
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{
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get { return m_stream.Position; }
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set { m_stream.Position = value; }
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}
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public override void SetLength (long value)
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{
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m_stream.SetLength (value);
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}
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public override long Seek (long offset, SeekOrigin origin)
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{
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return m_stream.Seek (offset, origin);
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}
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public override void Flush ()
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{
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m_stream.Flush();
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}
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}
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}
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