crc32.h

CRC校验采用多项式编码方法。多项式乘除法运算过程与普通代数多项式的乘除法相同。多项式的加减法运算以2为模

#ifndef CRC32_INCLUDED
#  define CRC32_INCLUDED

#include "defs.h"

/*
 * This code has some adaptations for the Ghostscript environment, but it
 * will compile and run correctly in any environment with 8-bit chars and
 * 32-bit ints.  Specifically, it assumes that if the following are
 * defined, they have the same meaning as in Ghostscript: P1, P2, P3.
 */

/* Define the state of the CRC32 Algorithm. */
typedef struct crc32_state_s {
    uint32_t count[2];	/* message length in bits, lsw first */
    uint32_t state[1];	/* digest buffer */
} CRC32_CTX;

#ifdef RUBY
#define CRC32_Init	rb_Digest_CRC32_Init
#define CRC32_Update	rb_Digest_CRC32_Update
#define CRC32_Final	rb_Digest_CRC32_Final
#define CRC32_End		rb_Digest_CRC32_End
#define CRC32_Equal	rb_Digest_CRC32_Equal
#endif

void	CRC32_Init _((CRC32_CTX *pms));
void	CRC32_Update _((CRC32_CTX *pms, const uint8_t *data, size_t nbytes));
void	CRC32_Final _((uint8_t *digest, CRC32_CTX *pms));
void	CRC32_End _((CRC32_CTX *pctx, uint8_t *hexdigest));
int	CRC32_Equal _((CRC32_CTX *pctx1, CRC32_CTX *pctx2));

#define CRC32_BLOCK_LENGTH		1
#define CRC32_DIGEST_LENGTH		4
#define CRC32_DIGEST_STRING_LENGTH	(CRC32_DIGEST_LENGTH * 2 + 1)

#endif /* CRC32_INCLUDED */