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/indra/llcommon/llcrc.cpp

https://bitbucket.org/lindenlab/viewer-beta/
C++ | 223 lines | 116 code | 30 blank | 77 comment | 7 complexity | cf46dcdc64bc81ac7e67267a585f1359 MD5 | raw file
  1/** 
  2 * @file llcrc.cpp
  3 * @brief implementation of the crc class.
  4 *
  5 * $LicenseInfo:firstyear=2002&license=viewerlgpl$
  6 * Second Life Viewer Source Code
  7 * Copyright (C) 2010, Linden Research, Inc.
  8 * 
  9 * This library is free software; you can redistribute it and/or
 10 * modify it under the terms of the GNU Lesser General Public
 11 * License as published by the Free Software Foundation;
 12 * version 2.1 of the License only.
 13 * 
 14 * This library is distributed in the hope that it will be useful,
 15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 17 * Lesser General Public License for more details.
 18 * 
 19 * You should have received a copy of the GNU Lesser General Public
 20 * License along with this library; if not, write to the Free Software
 21 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 22 * 
 23 * Linden Research, Inc., 945 Battery Street, San Francisco, CA  94111  USA
 24 * $/LicenseInfo$
 25 */
 26
 27#include "linden_common.h"
 28
 29#include "llcrc.h"
 30#include "llerror.h"
 31
 32/* Copyright (C) 1986 Gary S. Brown.  You may use this program, or
 33   code or tables extracted from it, as desired without restriction.*/
 34
 35/* First, the polynomial itself and its table of feedback terms.  The  */
 36/* polynomial is                                                       */
 37/* X^32+X^26+X^23+X^22+X^16+X^12+X^11+X^10+X^8+X^7+X^5+X^4+X^2+X^1+X^0 */
 38/* Note that we take it "backwards" and put the highest-order term in  */
 39/* the lowest-order bit.  The X^32 term is "implied"; the LSB is the   */
 40/* X^31 term, etc.  The X^0 term (usually shown as "+1") results in    */
 41/* the MSB being 1.                                                    */
 42
 43/* Note that the usual hardware shift register implementation, which   */
 44/* is what we're using (we're merely optimizing it by doing eight-bit  */
 45/* chunks at a time) shifts bits into the lowest-order term.  In our   */
 46/* implementation, that means shifting towards the right.  Why do we   */
 47/* do it this way?  Because the calculated CRC must be transmitted in  */
 48/* order from highest-order term to lowest-order term.  UARTs transmit */
 49/* characters in order from LSB to MSB.  By storing the CRC this way,  */
 50/* we hand it to the UART in the order low-byte to high-byte; the UART */
 51/* sends each low-bit to hight-bit; and the result is transmission bit */
 52/* by bit from highest- to lowest-order term without requiring any bit */
 53/* shuffling on our part.  Reception works similarly.                  */
 54
 55/* The feedback terms table consists of 256, 32-bit entries.  Notes:   */
 56/*                                                                     */
 57/*  1. The table can be generated at runtime if desired; code to do so */
 58/*     is shown later.  It might not be obvious, but the feedback      */
 59/*     terms simply represent the results of eight shift/xor opera-    */
 60/*     tions for all combinations of data and CRC register values.     */
 61/*                                                                     */
 62/*  2. The CRC accumulation logic is the same for all CRC polynomials, */
 63/*     be they sixteen or thirty-two bits wide.  You simply choose the */
 64/*     appropriate table.  Alternatively, because the table can be     */
 65/*     generated at runtime, you can start by generating the table for */
 66/*     the polynomial in question and use exactly the same "updcrc",   */
 67/*     if your application needn't simultaneously handle two CRC       */
 68/*     polynomials.  (Note, however, that XMODEM is strange.)          */
 69/*                                                                     */
 70/*  3. For 16-bit CRCs, the table entries need be only 16 bits wide;   */
 71/*     of course, 32-bit entries work OK if the high 16 bits are zero. */
 72/*                                                                     */
 73/*  4. The values must be right-shifted by eight bits by the "updcrc"  */
 74/*     logic; the shift must be unsigned (bring in zeroes).  On some   */
 75/*     hardware you could probably optimize the shift in assembler by  */
 76/*     using byte-swap instructions.                                   */
 77
 78///----------------------------------------------------------------------------
 79/// Local function declarations, constants, enums, and typedefs
 80///----------------------------------------------------------------------------
 81
 82#define UPDC32(octet,crc) (crc_32_tab[((crc) \
 83 ^ ((U8)octet)) & 0xff] ^ ((crc) >> 8))
 84
 85
 86static U32 crc_32_tab[] = { /* CRC polynomial 0xedb88320 */
 870x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f,
 880xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988,
 890x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91, 0x1db71064, 0x6ab020f2,
 900xf3b97148, 0x84be41de, 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7,
 910x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
 920xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172,
 930x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b, 0x35b5a8fa, 0x42b2986c,
 940xdbbbc9d6, 0xacbcf940, 0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59,
 950x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423,
 960xcfba9599, 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
 970x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190, 0x01db7106,
 980x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433,
 990x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d,
1000x91646c97, 0xe6635c01, 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e,
1010x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
1020x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65,
1030x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2, 0x4adfa541, 0x3dd895d7,
1040xa4d1c46d, 0xd3d6f4fb, 0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0,
1050x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa,
1060xbe0b1010, 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
1070x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, 0x2eb40d81,
1080xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a,
1090xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683, 0xe3630b12, 0x94643b84,
1100x0d6d6a3e, 0x7a6a5aa8, 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1,
1110xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
1120x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc,
1130xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5, 0xd6d6a3e8, 0xa1d1937e,
1140x38d8c2c4, 0x4fdff252, 0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,
1150xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55,
1160x316e8eef, 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
1170xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe, 0xb2bd0b28,
1180x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d,
1190x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a, 0x9c0906a9, 0xeb0e363f,
1200x72076785, 0x05005713, 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38,
1210x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
1220x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777,
1230x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c, 0x8f659eff, 0xf862ae69,
1240x616bffd3, 0x166ccf45, 0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2,
1250xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc,
1260x40df0b66, 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
1270xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605, 0xcdd70693,
1280x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94,
1290xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d
130};
131
132
133///----------------------------------------------------------------------------
134/// Class llcrc
135///----------------------------------------------------------------------------
136
137// Default constructor
138LLCRC::LLCRC() : mCurrent(0xffffffff)
139{
140}
141
142
143U32 LLCRC::getCRC() const
144{
145	return ~mCurrent;
146}
147
148void LLCRC::update(U8 next_byte)
149{
150	mCurrent = UPDC32(next_byte, mCurrent);
151}
152
153void LLCRC::update(const U8* buffer, size_t buffer_size)
154{
155	for (size_t i = 0; i < buffer_size; i++)
156	{
157		mCurrent = UPDC32(buffer[i], mCurrent);
158	}
159}
160
161void LLCRC::update(const std::string& filename)
162{
163	if (filename.empty())
164	{
165		llerrs << "No filename specified" << llendl;
166		return;
167	}
168
169	FILE* fp = LLFile::fopen(filename, "rb");		/* Flawfinder: ignore */
170
171	if (fp)
172	{
173		fseek(fp, 0, SEEK_END);
174		long size = ftell(fp);
175
176		fseek(fp, 0, SEEK_SET);
177
178		if (size > 0)
179		{
180			U8* data = new U8[size];
181			size_t nread;
182			
183			nread = fread(data, 1, size, fp);
184			fclose(fp);
185			
186			if (nread < (size_t) size)
187			{
188				llwarns << "Short read on " << filename << llendl;
189			}
190
191			update(data, nread);
192			delete[] data;
193		}
194		else
195		{
196			fclose(fp);
197		}
198	}
199}
200
201
202#ifdef _DEBUG
203BOOL LLCRC::testHarness()
204{
205	const S32 TEST_BUFFER_SIZE = 16;
206	const char TEST_BUFFER[TEST_BUFFER_SIZE] = "hello &#$)$&Nd0";	/* Flawfinder: ignore */
207	LLCRC c1, c2;
208	c1.update((U8*)TEST_BUFFER, TEST_BUFFER_SIZE - 1);
209	char* rh = (char*)TEST_BUFFER;
210	while(*rh != '\0')
211	{
212		c2.update(*rh);
213		++rh;
214	}
215	return(c1.getCRC() == c2.getCRC());
216}
217#endif
218
219
220
221///----------------------------------------------------------------------------
222/// Local function definitions
223///----------------------------------------------------------------------------