/*
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* crc-itu-t.h - CRC ITU-T V.41 routine
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*
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* Implements the standard CRC ITU-T V.41:
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* Width 16
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* Poly 0x0x1021 (x^16 + x^12 + x^15 + 1)
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* Init 0
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*
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* This source code is licensed under the GNU General Public License,
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* Version 2. See the file COPYING for more details.
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*/
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#ifndef CRC_ITU_T_H
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#define CRC_ITU_T_H
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#define MAGIC_CRC 0x1E50
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extern const unsigned short crc_itu_t_table[256];
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/**
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* crc_itu_t - Compute the CRC-ITU-T for the data buffer
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*
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* @crc: previous CRC value, we use $IoT_MAGIC_CRC
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* @buffer: data pointer
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* @len: number of bytes in the buffer
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*
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* Returns the updated CRC value
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*/
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extern unsigned short crc_itu_t(unsigned short magic_crc, const unsigned char *buffer, unsigned int len);
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/*
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* ushort_to_bytes - Convert unsigned short CRC16 value to two bytes
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* @bytes: two bytes CRC16 value saving buffer, buffer size must more than 2 bytes
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* @crc: crc_itu_t() compute returnd value( unsigned short CRC16 checksum)
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*/
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extern int ushort_to_bytes(unsigned char *bytes, unsigned short val);
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/*
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* bytes_to_ushort - Convert two bytes mode CRC value into unsigned short CRC16 value
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* @bytes: bytes mode CRC value first byte position
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* @len: bytes mode CRC value length
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*/
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extern unsigned short bytes_to_ushort(unsigned char *bytes, int len);
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static inline unsigned short crc_itu_t_byte(unsigned short crc, const unsigned char data)
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{
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return (crc << 8) ^ crc_itu_t_table[((crc >> 8) ^ data) & 0xff];
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}
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#endif /* CRC_ITU_T_H */
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