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Diffstat (limited to 'indra/llcommon/llcrc.cpp')
| -rw-r--r-- | indra/llcommon/llcrc.cpp | 224 |
1 files changed, 224 insertions, 0 deletions
diff --git a/indra/llcommon/llcrc.cpp b/indra/llcommon/llcrc.cpp new file mode 100644 index 0000000000..0836ccb66b --- /dev/null +++ b/indra/llcommon/llcrc.cpp @@ -0,0 +1,224 @@ +/** + * @file llcrc.cpp + * @brief implementation of the crc class. + * + * $LicenseInfo:firstyear=2002&license=viewergpl$ + * + * Copyright (c) 2002-2007, Linden Research, Inc. + * + * Second Life Viewer Source Code + * The source code in this file ("Source Code") is provided by Linden Lab + * to you under the terms of the GNU General Public License, version 2.0 + * ("GPL"), unless you have obtained a separate licensing agreement + * ("Other License"), formally executed by you and Linden Lab. Terms of + * the GPL can be found in doc/GPL-license.txt in this distribution, or + * online at http://secondlife.com/developers/opensource/gplv2 + * + * There are special exceptions to the terms and conditions of the GPL as + * it is applied to this Source Code. View the full text of the exception + * in the file doc/FLOSS-exception.txt in this software distribution, or + * online at http://secondlife.com/developers/opensource/flossexception + * + * By copying, modifying or distributing this software, you acknowledge + * that you have read and understood your obligations described above, + * and agree to abide by those obligations. + * + * ALL LINDEN LAB SOURCE CODE IS PROVIDED "AS IS." LINDEN LAB MAKES NO + * WARRANTIES, EXPRESS, IMPLIED OR OTHERWISE, REGARDING ITS ACCURACY, + * COMPLETENESS OR PERFORMANCE. + * $/LicenseInfo$ + */ + +#include "linden_common.h" + +#include "llcrc.h" +#include "llerror.h" + +/* Copyright (C) 1986 Gary S. Brown. You may use this program, or + code or tables extracted from it, as desired without restriction.*/ + +/* First, the polynomial itself and its table of feedback terms. The */ +/* polynomial is */ +/* 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 */ +/* Note that we take it "backwards" and put the highest-order term in */ +/* the lowest-order bit. The X^32 term is "implied"; the LSB is the */ +/* X^31 term, etc. The X^0 term (usually shown as "+1") results in */ +/* the MSB being 1. */ + +/* Note that the usual hardware shift register implementation, which */ +/* is what we're using (we're merely optimizing it by doing eight-bit */ +/* chunks at a time) shifts bits into the lowest-order term. In our */ +/* implementation, that means shifting towards the right. Why do we */ +/* do it this way? Because the calculated CRC must be transmitted in */ +/* order from highest-order term to lowest-order term. UARTs transmit */ +/* characters in order from LSB to MSB. By storing the CRC this way, */ +/* we hand it to the UART in the order low-byte to high-byte; the UART */ +/* sends each low-bit to hight-bit; and the result is transmission bit */ +/* by bit from highest- to lowest-order term without requiring any bit */ +/* shuffling on our part. Reception works similarly. */ + +/* The feedback terms table consists of 256, 32-bit entries. Notes: */ +/* */ +/* 1. The table can be generated at runtime if desired; code to do so */ +/* is shown later. It might not be obvious, but the feedback */ +/* terms simply represent the results of eight shift/xor opera- */ +/* tions for all combinations of data and CRC register values. */ +/* */ +/* 2. The CRC accumulation logic is the same for all CRC polynomials, */ +/* be they sixteen or thirty-two bits wide. You simply choose the */ +/* appropriate table. Alternatively, because the table can be */ +/* generated at runtime, you can start by generating the table for */ +/* the polynomial in question and use exactly the same "updcrc", */ +/* if your application needn't simultaneously handle two CRC */ +/* polynomials. (Note, however, that XMODEM is strange.) */ +/* */ +/* 3. For 16-bit CRCs, the table entries need be only 16 bits wide; */ +/* of course, 32-bit entries work OK if the high 16 bits are zero. */ +/* */ +/* 4. The values must be right-shifted by eight bits by the "updcrc" */ +/* logic; the shift must be unsigned (bring in zeroes). On some */ +/* hardware you could probably optimize the shift in assembler by */ +/* using byte-swap instructions. */ + +///---------------------------------------------------------------------------- +/// Local function declarations, constants, enums, and typedefs +///---------------------------------------------------------------------------- + +#define UPDC32(octet,crc) (crc_32_tab[((crc) \ + ^ ((U8)octet)) & 0xff] ^ ((crc) >> 8)) + + +static U32 crc_32_tab[] = { /* CRC polynomial 0xedb88320 */ +0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f, +0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988, +0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91, 0x1db71064, 0x6ab020f2, +0xf3b97148, 0x84be41de, 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, +0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9, +0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172, +0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b, 0x35b5a8fa, 0x42b2986c, +0xdbbbc9d6, 0xacbcf940, 0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59, +0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, +0xcfba9599, 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924, +0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190, 0x01db7106, +0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433, +0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, +0x91646c97, 0xe6635c01, 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, +0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950, +0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65, +0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2, 0x4adfa541, 0x3dd895d7, +0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0, +0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, +0xbe0b1010, 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f, +0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, 0x2eb40d81, +0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a, +0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683, 0xe3630b12, 0x94643b84, +0x0d6d6a3e, 0x7a6a5aa8, 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, +0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb, +0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc, +0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5, 0xd6d6a3e8, 0xa1d1937e, +0x38d8c2c4, 0x4fdff252, 0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b, +0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, +0x316e8eef, 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236, +0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe, 0xb2bd0b28, +0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d, +0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a, 0x9c0906a9, 0xeb0e363f, +0x72076785, 0x05005713, 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, +0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242, +0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777, +0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c, 0x8f659eff, 0xf862ae69, +0x616bffd3, 0x166ccf45, 0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2, +0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, +0x40df0b66, 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9, +0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605, 0xcdd70693, +0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94, +0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d +}; + + +///---------------------------------------------------------------------------- +/// Class llcrc +///---------------------------------------------------------------------------- + +// Default constructor +LLCRC::LLCRC() : mCurrent(0xffffffff) +{ +} + + +U32 LLCRC::getCRC() const +{ + return ~mCurrent; +} + +void LLCRC::update(U8 next_byte) +{ + mCurrent = UPDC32(next_byte, mCurrent); +} + +void LLCRC::update(const U8* buffer, size_t buffer_size) +{ + for (size_t i = 0; i < buffer_size; i++) + { + mCurrent = UPDC32(buffer[i], mCurrent); + } +} + +void LLCRC::update(const char* filename) +{ + if (!filename) + { + llerrs << "No filename specified" << llendl; + return; + } + + FILE* fp = LLFile::fopen(filename, "rb"); /* Flawfinder: ignore */ + + if (fp) + { + fseek(fp, 0, SEEK_END); + long size = ftell(fp); + + fseek(fp, 0, SEEK_SET); + + if (size > 0) + { + U8* data = new U8[size]; + size_t nread; + + nread = fread(data, 1, size, fp); + fclose(fp); + + if (nread < (size_t) size) + { + llwarns << "Short read on " << filename << llendl; + } + + update(data, nread); + delete[] data; + } + } +} + + +#ifdef _DEBUG +BOOL LLCRC::testHarness() +{ + const S32 TEST_BUFFER_SIZE = 16; + const char TEST_BUFFER[TEST_BUFFER_SIZE] = "hello &#$)$&Nd0"; /* Flawfinder: ignore */ + LLCRC c1, c2; + c1.update((U8*)TEST_BUFFER, TEST_BUFFER_SIZE - 1); + char* rh = (char*)TEST_BUFFER; + while(*rh != '\0') + { + c2.update(*rh); + ++rh; + } + return(c1.getCRC() == c2.getCRC()); +} +#endif + + + +///---------------------------------------------------------------------------- +/// Local function definitions +///---------------------------------------------------------------------------- |