diff options
Diffstat (limited to 'apt-pkg/contrib')
| -rw-r--r-- | apt-pkg/contrib/crc-16.cc | 76 | ||||
| -rw-r--r-- | apt-pkg/contrib/crc-16.h | 21 |
2 files changed, 97 insertions, 0 deletions
diff --git a/apt-pkg/contrib/crc-16.cc b/apt-pkg/contrib/crc-16.cc new file mode 100644 index 000000000..52a551802 --- /dev/null +++ b/apt-pkg/contrib/crc-16.cc @@ -0,0 +1,76 @@ +// -*- mode: cpp; mode: fold -*- +// Description /*{{{*/ +// $Id: crc-16.cc,v 1.1 1999/05/23 22:55:54 jgg Exp $ +/* ###################################################################### + + CRC16 - Compute a 16bit crc very quickly + + This was ripped out of the linux 2.2 kernel source (irda/crc.c) and + is credited to ppp.c by Michael Callahan <callahan@maths.ox.ac.uk> and + Al Longyear <longyear@netcom.com> + + Modified by Jason Gunthorpe <jgg@debian.org> to fit the local coding + style, this code is belived to be in the Public Domain. + + ##################################################################### */ + /*}}}*/ +// Include Files /*{{{*/ +#ifdef __GNUG__ +#pragma implementation "apt-pkg/crc-16.h" +#endif + +#include <apt-pkg/crc-16.h> + /*}}}*/ + +/* + * This mysterious table is just the CRC of each possible byte. It can be + * computed using the standard bit-at-a-time methods. The polynomial can + * be seen in entry 128, 0x8408. This corresponds to x^0 + x^5 + x^12. + * Add the implicit x^16, and you have the standard CRC-CCITT. + */ +static unsigned short const crc16_table[256] = +{ + 0x0000, 0x1189, 0x2312, 0x329b, 0x4624, 0x57ad, 0x6536, 0x74bf, + 0x8c48, 0x9dc1, 0xaf5a, 0xbed3, 0xca6c, 0xdbe5, 0xe97e, 0xf8f7, + 0x1081, 0x0108, 0x3393, 0x221a, 0x56a5, 0x472c, 0x75b7, 0x643e, + 0x9cc9, 0x8d40, 0xbfdb, 0xae52, 0xdaed, 0xcb64, 0xf9ff, 0xe876, + 0x2102, 0x308b, 0x0210, 0x1399, 0x6726, 0x76af, 0x4434, 0x55bd, + 0xad4a, 0xbcc3, 0x8e58, 0x9fd1, 0xeb6e, 0xfae7, 0xc87c, 0xd9f5, + 0x3183, 0x200a, 0x1291, 0x0318, 0x77a7, 0x662e, 0x54b5, 0x453c, + 0xbdcb, 0xac42, 0x9ed9, 0x8f50, 0xfbef, 0xea66, 0xd8fd, 0xc974, + 0x4204, 0x538d, 0x6116, 0x709f, 0x0420, 0x15a9, 0x2732, 0x36bb, + 0xce4c, 0xdfc5, 0xed5e, 0xfcd7, 0x8868, 0x99e1, 0xab7a, 0xbaf3, + 0x5285, 0x430c, 0x7197, 0x601e, 0x14a1, 0x0528, 0x37b3, 0x263a, + 0xdecd, 0xcf44, 0xfddf, 0xec56, 0x98e9, 0x8960, 0xbbfb, 0xaa72, + 0x6306, 0x728f, 0x4014, 0x519d, 0x2522, 0x34ab, 0x0630, 0x17b9, + 0xef4e, 0xfec7, 0xcc5c, 0xddd5, 0xa96a, 0xb8e3, 0x8a78, 0x9bf1, + 0x7387, 0x620e, 0x5095, 0x411c, 0x35a3, 0x242a, 0x16b1, 0x0738, + 0xffcf, 0xee46, 0xdcdd, 0xcd54, 0xb9eb, 0xa862, 0x9af9, 0x8b70, + 0x8408, 0x9581, 0xa71a, 0xb693, 0xc22c, 0xd3a5, 0xe13e, 0xf0b7, + 0x0840, 0x19c9, 0x2b52, 0x3adb, 0x4e64, 0x5fed, 0x6d76, 0x7cff, + 0x9489, 0x8500, 0xb79b, 0xa612, 0xd2ad, 0xc324, 0xf1bf, 0xe036, + 0x18c1, 0x0948, 0x3bd3, 0x2a5a, 0x5ee5, 0x4f6c, 0x7df7, 0x6c7e, + 0xa50a, 0xb483, 0x8618, 0x9791, 0xe32e, 0xf2a7, 0xc03c, 0xd1b5, + 0x2942, 0x38cb, 0x0a50, 0x1bd9, 0x6f66, 0x7eef, 0x4c74, 0x5dfd, + 0xb58b, 0xa402, 0x9699, 0x8710, 0xf3af, 0xe226, 0xd0bd, 0xc134, + 0x39c3, 0x284a, 0x1ad1, 0x0b58, 0x7fe7, 0x6e6e, 0x5cf5, 0x4d7c, + 0xc60c, 0xd785, 0xe51e, 0xf497, 0x8028, 0x91a1, 0xa33a, 0xb2b3, + 0x4a44, 0x5bcd, 0x6956, 0x78df, 0x0c60, 0x1de9, 0x2f72, 0x3efb, + 0xd68d, 0xc704, 0xf59f, 0xe416, 0x90a9, 0x8120, 0xb3bb, 0xa232, + 0x5ac5, 0x4b4c, 0x79d7, 0x685e, 0x1ce1, 0x0d68, 0x3ff3, 0x2e7a, + 0xe70e, 0xf687, 0xc41c, 0xd595, 0xa12a, 0xb0a3, 0x8238, 0x93b1, + 0x6b46, 0x7acf, 0x4854, 0x59dd, 0x2d62, 0x3ceb, 0x0e70, 0x1ff9, + 0xf78f, 0xe606, 0xd49d, 0xc514, 0xb1ab, 0xa022, 0x92b9, 0x8330, + 0x7bc7, 0x6a4e, 0x58d5, 0x495c, 0x3de3, 0x2c6a, 0x1ef1, 0x0f78 +}; + +/* Recompute the FCS with one more character appended. */ +#define CalcFCS(fcs, c) (((fcs) >> 8) ^ crc16_table[((fcs) ^ (c)) & 0xff]) +unsigned short AddCRC16(unsigned short fcs, void const *Buf, + unsigned long len) +{ + unsigned char const *buf = (unsigned char const *)Buf; + while (len--) + fcs = CalcFCS(fcs, *buf++); + return fcs; +} diff --git a/apt-pkg/contrib/crc-16.h b/apt-pkg/contrib/crc-16.h new file mode 100644 index 000000000..757104c54 --- /dev/null +++ b/apt-pkg/contrib/crc-16.h @@ -0,0 +1,21 @@ +// -*- mode: cpp; mode: fold -*- +// Description /*{{{*/ +// $Id: crc-16.h,v 1.1 1999/05/23 22:55:54 jgg Exp $ +/* ###################################################################### + + CRC16 - Compute a 16bit crc very quickly + + ##################################################################### */ + /*}}}*/ +#ifndef APTPKG_CRC16_H +#define APTPKG_CRC16_H + +#ifdef __GNUG__ +#pragma interface "apt-pkg/crc-16.h" +#endif + +#define INIT_FCS 0xffff +unsigned short AddCRC16(unsigned short fcs, void const *buf, + unsigned long len); + +#endif |