smallwe.cpp

来自「在单片机上实现crc校验」· C++ 代码 · 共 37 行

const unsigned long cnCRC_32 = 0x04C10DB7; 
// CRC-32 = X32 + X26 + X23 + X22 + X16 + X11 + X10 + X8 + X7 + X5 + X4 + X2 + X1 + X0 
unsigned long Table_CRC[256]; // CRC 表 
// 构造 32 位 CRC 表 
void BuildTable32( unsigned long aPoly ) 
{ 
unsigned long i, j; 
unsigned long nData; 
unsigned long nAccum; 

for ( i = 0; i < 256; i++ ) 
{ 
nData = ( unsigned long )( i << 24 ); 
nAccum = 0; 
for ( j = 0; j < 8; j++ ) 
{ 
if ( ( nData ^ nAccum ) & 0x80000000 ) 
nAccum = ( nAccum << 1 ) ^ aPoly; 
else 
nAccum <<= 1; 
nData <<= 1; 
} 
Table_CRC[i] = nAccum; 
} 
} 

// 计算 32 位 CRC-32 值 
unsigned long CRC_32( unsigned char * aData, unsigned long aSize ) 
{ 
unsigned long i; 
unsigned long nAccum = 0; 

BuildTable32( cnCRC_32 ); 
for ( i = 0; i < aSize; i++ ) 
nAccum = ( nAccum << 8 ) ^ Table_CRC[( nAccum >> 24 ) ^ *aData++]; 
return nAccum; 
}