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Use a 4-bit table to speed up the CRC even further, without increasing the 

code size too much.
This commit is contained in:
mycroft 1998-03-29 23:02:27 +00:00
parent 81a5bfdf33
commit 5d8b98c7b1
1 changed files with 13 additions and 13 deletions
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26
sys/dev/isa/if_fe.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: if_fe.c,v 1.21 1998/03/22 12:48:41 drochner Exp $ */
/* $NetBSD: if_fe.c,v 1.22 1998/03/29 23:02:27 mycroft Exp $ */
/*
* All Rights Reserved, Copyright (C) Fujitsu Limited 1995
@ -2307,9 +2307,15 @@ fe_getmcaf(ec, af)
{
struct ifnet *ifp = &ec->ec_if;
struct ether_multi *enm;
register u_char *cp, c;
register u_long crc;
register int i, len;
register u_char *cp;
register u_int32_t crc;
static const u_int32_t crctab[] = {
0x00000000, 0x1db71064, 0x3b6e20c8, 0x26d930ac,
0x76dc4190, 0x6b6b51f4, 0x4db26158, 0x5005713c,
0xedb88320, 0xf00f9344, 0xd6d6a3e8, 0xcb61b38c,
0x9b64c2b0, 0x86d3d2d4, 0xa00ae278, 0xbdbdf21c
};
register int len;
struct ether_multistep step;
/*
@ -2342,15 +2348,9 @@ fe_getmcaf(ec, af)
cp = enm->enm_addrlo;
crc = 0xffffffff;
for (len = sizeof(enm->enm_addrlo); --len >= 0;) {
c = *cp++;
for (i = 8; --i >= 0;) {
if ((crc & 0x01) ^ (c & 0x01)) {
crc >>= 1;
crc ^= 0xedb88320;
} else
crc >>= 1;
c >>= 1;
}
crc ^= *cp++;
crc = (crc >> 4) ^ crctab[crc & 0xf];
crc = (crc >> 4) ^ crctab[crc & 0xf];
}
/* Just want the 6 most significant bits. */
crc >>= 26;