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/**
 *  @file  crc.h
 *  @brief CRC functions.
 */


#ifndef _CRC_H_
#define _CRC_H_

#include <stdint.h>

#ifdef __cplusplus
extern "C" {
#endif


/* Multi-binary functions */

/**
 * @brief Generate CRC from the T10 standard, runs appropriate version.
 *
 * This function determines what instruction sets are enabled and
 * selects the appropriate version at runtime.
 *
 * @returns 16 bit CRC
 */
uint16_t crc16_t10dif(
	uint16_t init_crc,        //!< initial CRC value, 16 bits
	const unsigned char *buf, //!< buffer to calculate CRC on
	uint64_t len              //!< buffer length in bytes (64-bit data)
	);


/**
 * @brief Generate CRC from the IEEE standard, runs appropriate version.
 *
 * This function determines what instruction sets are enabled and
 * selects the appropriate version at runtime.
 * Note: CRC32 IEEE standard is widely used in HDLC, Ethernet, Gzip and
 * many others. Its polynomial is 0x04C11DB7 in normal and 0xEDB88320
 * in reflection (or reverse). In ISA-L CRC, function crc32_ieee is
 * actually designed for normal CRC32 IEEE version. And function
 * crc32_gzip_refl is actually designed for reflected CRC32 IEEE.
 * These two versions of CRC32 IEEE are not compatible with each other.
 * Users who want to replace their not optimized crc32 ieee with ISA-L's
 * crc32 function should be careful of that.
 * Since many applications use CRC32 IEEE reflected version, Please have
 * a check whether crc32_gzip_refl is right one for you instead of
 * crc32_ieee.
 *
 * @returns 32 bit CRC
 */

uint32_t crc32_ieee(
	uint32_t init_crc,        //!< initial CRC value, 32 bits
	const unsigned char *buf, //!< buffer to calculate CRC on
	uint64_t len              //!< buffer length in bytes (64-bit data)
	);

/**
 * @brief Generate the customized CRC
 * based on RFC 1952 CRC (http://www.ietf.org/rfc/rfc1952.txt) standard,
 * runs appropriate version.
 *
 * This function determines what instruction sets are enabled and
 * selects the appropriate version at runtime.
 *
 * Note: CRC32 IEEE standard is widely used in HDLC, Ethernet, Gzip and
 * many others. Its polynomial is 0x04C11DB7 in normal and 0xEDB88320
 * in reflection (or reverse). In ISA-L CRC, function crc32_ieee is
 * actually designed for normal CRC32 IEEE version. And function
 * crc32_gzip_refl is actually designed for reflected CRC32 IEEE.
 * These two versions of CRC32 IEEE are not compatible with each other.
 * Users who want to replace their not optimized crc32 ieee with ISA-L's
 * crc32 function should be careful of that.
 * Since many applications use CRC32 IEEE reflected version, Please have
 * a check whether crc32_gzip_refl is right one for you instead of
 * crc32_ieee.
 *
 * @returns 32 bit CRC
 */
uint32_t crc32_gzip_refl(
	uint32_t init_crc,          //!< initial CRC value, 32 bits
	const unsigned char *buf, //!< buffer to calculate CRC on
	uint64_t len                //!< buffer length in bytes (64-bit data)
	);


/**
 * @brief ISCSI CRC function, runs appropriate version.
 *
 * This function determines what instruction sets are enabled and
 * selects the appropriate version at runtime.
 *
 * @returns 32 bit CRC
 */
unsigned int crc32_iscsi(
	unsigned char *buffer, //!< buffer to calculate CRC on
	int len,               //!< buffer length in bytes
	unsigned int init_crc  //!< initial CRC value
	);


/* Base functions */

/**
 * @brief ISCSI CRC function, baseline version
 * @returns 32 bit CRC
 */
unsigned int crc32_iscsi_base(
	unsigned char *buffer,	//!< buffer to calculate CRC on
	int len, 		//!< buffer length in bytes
	unsigned int crc_init	//!< initial CRC value
	);


/**
 * @brief Generate CRC from the T10 standard, runs baseline version
 * @returns 16 bit CRC
 */
uint16_t crc16_t10dif_base(
	uint16_t seed,	//!< initial CRC value, 16 bits
	uint8_t *buf,	//!< buffer to calculate CRC on
	uint64_t len 	//!< buffer length in bytes (64-bit data)
	);


/**
 * @brief Generate CRC from the IEEE standard, runs baseline version
 * @returns 32 bit CRC
 */
uint32_t crc32_ieee_base(
	uint32_t seed, 	//!< initial CRC value, 32 bits
	uint8_t *buf,	//!< buffer to calculate CRC on
	uint64_t len 	//!< buffer length in bytes (64-bit data)
	);

/**
 * @brief Generate the customized CRC
 * based on RFC 1952 CRC (http://www.ietf.org/rfc/rfc1952.txt) standard,
 * runs baseline version
 * @returns 32 bit CRC
 */
uint32_t crc32_gzip_refl_base(
	uint32_t seed,	//!< initial CRC value, 32 bits
	uint8_t *buf,	//!< buffer to calculate CRC on
	uint64_t len	//!< buffer length in bytes (64-bit data)
	);


#ifdef __cplusplus
}
#endif

#endif // _CRC_H_
