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53 lines
1.1 KiB
53 lines
1.1 KiB
#include <internal/crc.h>
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static const uint32_t __h_crc_poly = 0xedb88320u;
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static uint32_t __h_crc_table[_H_CRC_TABLE_SIZE];
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static _Atomic volatile int __h_crc_initialised=0;
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static _Atomic volatile int __initialising=0;
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static uint32_t* __h_crc_create_table(uint32_t* table, uint32_t poly)
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{
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register int i=0;
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for(;i<_H_CRC_TABLE_SIZE;i++)
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{
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register int j=0;
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uint32_t e = (uint32_t)i;
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for(;j<_H_CRC_ITERATIONS;j++)
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{
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if( (e&1) == 1)
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e = (e>>1) ^ poly;
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else e = e>>1;
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}
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table[i] = e;
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}
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return table;
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}
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static uint32_t __h_crc_calc(uint32_t* table, uint32_t seed, const unsigned char* buffer, int len)
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{
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uint32_t crc= seed;
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register int i=0;
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for(;i<len;i++)
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{
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crc = (crc>>8) ^ table[(buffer[i] ^ crc) & 0xff];
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}
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return crc;
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}
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unsigned long _h_crc32(unsigned long seed, const unsigned char* buffer,unsigned int len)
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{
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while(__initialising) (void)0;
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if(!__h_crc_initialised)
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{
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__initialising=1;
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__h_crc_create_table(__h_crc_table,__h_crc_poly);
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__h_crc_initialised=1;
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__initialising=0;
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}
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return ~__h_crc_calc(__h_crc_table, (uint32_t) seed, buffer, (int)len);
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}
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