**diff options**

author | Damien Miller <djm@mindrot.org> | 2000-09-16 13:29:08 +1100 |
---|---|---|

committer | Damien Miller <djm@mindrot.org> | 2000-09-16 13:29:08 +1100 |

commit | e4340be5b3ff16f4d9ba5e3ea7e449dc1b6fa7a8 (patch) | |

tree | aba9e2ae234edeb888b922c6a13b755c1248deea /crc32.c | |

parent | f384c366d33cb435627743f7ea0ed3f966543d40 (diff) |

- (djm) Merge OpenBSD changes:

- markus@cvs.openbsd.org 2000/09/05 02:59:57
[session.c]
print hostname (not hushlogin)
- markus@cvs.openbsd.org 2000/09/05 13:18:48
[authfile.c ssh-add.c]
enable ssh-add -d for DSA keys
- markus@cvs.openbsd.org 2000/09/05 13:20:49
[sftp-server.c]
cleanup
- markus@cvs.openbsd.org 2000/09/06 03:46:41
[authfile.h]
prototype
- deraadt@cvs.openbsd.org 2000/09/07 14:27:56
[ALL]
cleanup copyright notices on all files. I have attempted to be
accurate with the details. everything is now under Tatu's licence
(which I copied from his readme), and/or the core-sdi bsd-ish thing
for deattack, or various openbsd developers under a 2-term bsd
licence. We're not changing any rules, just being accurate.
- markus@cvs.openbsd.org 2000/09/07 14:40:30
[channels.c channels.h clientloop.c serverloop.c ssh.c]
cleanup window and packet sizes for ssh2 flow control; ok niels
- markus@cvs.openbsd.org 2000/09/07 14:53:00
[scp.c]
typo
- markus@cvs.openbsd.org 2000/09/07 15:13:37
[auth-options.c auth-options.h auth-rh-rsa.c auth-rsa.c auth.c]
[authfile.h canohost.c channels.h compat.c hostfile.h log.c match.h]
[pty.c readconf.c]
some more Copyright fixes
- markus@cvs.openbsd.org 2000/09/08 03:02:51
[README.openssh2]
bye bye
- deraadt@cvs.openbsd.org 2000/09/11 18:38:33
[LICENCE cipher.c]
a few more comments about it being ARC4 not RC4
- markus@cvs.openbsd.org 2000/09/12 14:53:11
[log-client.c log-server.c log.c ssh.1 ssh.c ssh.h sshd.8 sshd.c]
multiple debug levels
- markus@cvs.openbsd.org 2000/09/14 14:25:15
[clientloop.c]
typo
- deraadt@cvs.openbsd.org 2000/09/15 01:13:51
[ssh-agent.c]
check return value for setenv(3) for failure, and deal appropriately

Diffstat (limited to 'crc32.c')

-rw-r--r-- | crc32.c | 83 |

1 files changed, 38 insertions, 45 deletions

@@ -1,55 +1,48 @@ /* - * The implementation here was originally done by Gary S. Brown. - * I have borrowed the tables directly, and made some minor changes - * to the crc32-function (including changing the interface). - * //ylo + * 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 $edb88320 */ + #include "includes.h" -RCSID("$OpenBSD: crc32.c,v 1.6 2000/08/19 02:17:12 deraadt Exp $"); +RCSID("$OpenBSD: crc32.c,v 1.7 2000/09/07 20:27:51 deraadt Exp $"); #include "crc32.h" - /* ============================================================= */ - /* 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 */ - /* */ - /* -------------------------------------------------------------------- */ - static unsigned int crc32_tab[] = { 0x00000000L, 0x77073096L, 0xee0e612cL, 0x990951baL, 0x076dc419L, 0x706af48fL, 0xe963a535L, 0x9e6495a3L, 0x0edb8832L, 0x79dcb8a4L, |