/usr/include/ntirpc/rpc/rpc_cksum.h is in libntirpc-dev 1.3.1-1.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 | /*-
* COPYRIGHT (C) 1986 Gary S. Brown. You may use this program, or
* code or tables extracted from it, as desired without restriction.
*/
/*
* First, the polynomial itself and its table of feedback terms. The
* polynomial is
* X^32+X^26+X^23+X^22+X^16+X^12+X^11+X^10+X^8+X^7+X^5+X^4+X^2+X^1+X^0
*
* Note that we take it "backwards" and put the highest-order term in
* the lowest-order bit. The X^32 term is "implied"; the LSB is the
* X^31 term, etc. The X^0 term (usually shown as "+1") results in
* the MSB being 1
*
* Note that the usual hardware shift register implementation, which
* is what we're using (we're merely optimizing it by doing eight-bit
* chunks at a time) shifts bits into the lowest-order term. In our
* implementation, that means shifting towards the right. Why do we
* do it this way? Because the calculated CRC must be transmitted in
* order from highest-order term to lowest-order term. UARTs transmit
* characters in order from LSB to MSB. By storing the CRC this way
* we hand it to the UART in the order low-byte to high-byte; the UART
* sends each low-bit to hight-bit; and the result is transmission bit
* by bit from highest- to lowest-order term without requiring any bit
* shuffling on our part. Reception works similarly
*
* The feedback terms table consists of 256, 32-bit entries. Notes
*
* The table can be generated at runtime if desired; code to do so
* is shown later. It might not be obvious, but the feedback
* terms simply represent the results of eight shift/xor opera
* tions for all combinations of data and CRC register values
*
* The values must be right-shifted by eight bits by the "updcrc
* logic; the shift must be unsigned (bring in zeroes). On some
* hardware you could probably optimize the shift in assembler by
* using byte-swap instructions
* polynomial $edb88320
*
*
* CRC32 code derived from work by Gary S. Brown.
*/
#ifndef RPC_CKSUM_H
#define RPC_CKSUM_H
/* table-driven, software crc32c */
uint32_t calculate_crc32c(uint32_t crc32c, const unsigned char *buffer,
unsigned int length);
#endif /* RPC_CKSUM_H */
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