Visualization Library v1.0.3A lightweight C++ OpenGL middleware for 2D/3D graphics |
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00001 /**************************************************************************************/ 00002 /* */ 00003 /* Visualization Library */ 00004 /* http://visualizationlibrary.org */ 00005 /* */ 00006 /* Copyright (c) 2005-2010, Michele Bosi */ 00007 /* All rights reserved. */ 00008 /* */ 00009 /* Redistribution and use in source and binary forms, with or without modification, */ 00010 /* are permitted provided that the following conditions are met: */ 00011 /* */ 00012 /* - Redistributions of source code must retain the above copyright notice, this */ 00013 /* list of conditions and the following disclaimer. */ 00014 /* */ 00015 /* - Redistributions in binary form must reproduce the above copyright notice, this */ 00016 /* list of conditions and the following disclaimer in the documentation and/or */ 00017 /* other materials provided with the distribution. */ 00018 /* */ 00019 /* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND */ 00020 /* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED */ 00021 /* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE */ 00022 /* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR */ 00023 /* ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES */ 00024 /* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; */ 00025 /* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON */ 00026 /* ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT */ 00027 /* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS */ 00028 /* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ 00029 /* */ 00030 /**************************************************************************************/ 00031 00032 #ifndef CRC32CheckSum_INCLUDE_ONCE 00033 #define CRC32CheckSum_INCLUDE_ONCE 00034 00035 #include <vlCore/VirtualFile.hpp> 00036 00037 namespace vl 00038 { 00042 class CRC32CheckSum 00043 { 00044 // Lower this if you need to limit the amount of data allocated to the stack, for example to 16K. 00045 static const int CHUNK_SIZE = 128*1024; 00046 00047 public: 00049 CRC32CheckSum() { crc32_init(); } 00050 00051 unsigned int compute(const void* buf, int length) 00052 { 00053 const unsigned char* buffer = (const unsigned char*)buf; 00054 unsigned int mCRC32 = 0xffffffff; 00055 while(length--) 00056 mCRC32 = (mCRC32 >> 8) ^ crc32_table[(mCRC32 & 0xFF) ^ *buffer++]; 00057 return mCRC32 ^ 0xffffffff; 00058 } 00059 00060 unsigned int compute(VirtualFile* stream) 00061 { 00062 std::vector<unsigned char> buffer; 00063 buffer.resize(CHUNK_SIZE); 00064 unsigned char *ptr = &buffer.front(); 00065 startCRC32(); 00066 00067 for( int length = (int)stream->read(ptr, CHUNK_SIZE); length; length = (int)stream->read(ptr, CHUNK_SIZE) ) 00068 continueCRC32(ptr,length); 00069 00070 return finalizeCRC32(); 00071 } 00072 00073 void startCRC32() { mCRC32 = 0xffffffff; } 00074 unsigned int finalizeCRC32() { return mCRC32 ^ 0xffffffff; } 00075 void continueCRC32(unsigned char* ptr, int length) 00076 { 00077 while(length--) 00078 mCRC32 = (mCRC32 >> 8) ^ crc32_table[(mCRC32 & 0xFF) ^ *ptr++]; 00079 } 00080 00081 protected: 00082 void crc32_init() 00083 { 00084 mCRC32 = 0; 00085 unsigned int ulPolynomial = 0x04c11db7; 00086 for(int i = 0; i <= 0xFF; i++) 00087 { 00088 crc32_table[i]=reflect(i, 8) << 24; 00089 for (int j = 0; j < 8; j++) 00090 crc32_table[i] = (crc32_table[i] << 1) ^ (crc32_table[i] & (1 << 31) ? ulPolynomial : 0); 00091 crc32_table[i] = reflect(crc32_table[i], 32); 00092 } 00093 } 00094 00095 unsigned int reflect(unsigned int val, char ch) 00096 { 00097 unsigned int refl = 0; 00098 for(int i = 1; i < (ch + 1); i++) 00099 { 00100 if(val & 1) 00101 refl |= 1 << (ch - i); 00102 val >>= 1; 00103 } 00104 return refl; 00105 } 00106 00107 protected: 00108 unsigned int mCRC32; 00109 unsigned int crc32_table[256]; 00110 }; 00111 } 00112 00113 #endif