Aren/NetBSD
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Garbage-collect the DYNAMIC_CRC_TABLE stuff. The table it computed

Browse Source 
was incompatible with the new CRC code, and it is largely unnecessary
now, since the static table is so much smaller.

Fixes PR kern/20935.
This commit is contained in:
thorpej 2003-03-29 22:25:25 +00:00
parent bb218b78eb
commit 7a3fa51b7f
2 changed files with 3 additions and 67 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
sys/arch/evbarm/stand/gzboot/Makefile.gzboot
View File

@ -1,4 +1,4 @@
# $NetBSD: Makefile.gzboot,v 1.5 2002/04/25 22:30:38 thorpej Exp $
# $NetBSD: Makefile.gzboot,v 1.6 2003/03/29 22:25:25 thorpej Exp $
NOMAN= # defined
@ -41,9 +41,6 @@ CPPFLAGS+= -DHEAP_SIZE=1048576 # 1M
# libsa options
CPPFLAGS+= -DHEAP_VARIABLE
# libz options
CPPFLAGS+= -DDYNAMIC_CRC_TABLE
CPPFLAGS+= -DRELOC=${RELOC}
CPPFLAGS+= -DMAXIMAGESIZE=${MAXIMAGESIZE}
CPPFLAGS+= -DLOADADDR=${LOADADDR}

65
sys/lib/libz/crc32.c
View File

@ -1,79 +1,22 @@
/* $NetBSD: crc32.c,v 1.5 2003/03/25 22:48:44 mycroft Exp $ */
/* $NetBSD: crc32.c,v 1.6 2003/03/29 22:25:26 thorpej Exp $ */
/* crc32.c -- compute the CRC-32 of a data stream
* Copyright (C) 1995-2002 Mark Adler
* For conditions of distribution and use, see copyright notice in zlib.h
*/
/* @(#) $Id: crc32.c,v 1.5 2003/03/25 22:48:44 mycroft Exp $ */
/* @(#) $Id: crc32.c,v 1.6 2003/03/29 22:25:26 thorpej Exp $ */
#include "zlib.h"
#define local static
#ifdef DYNAMIC_CRC_TABLE
local int crc_table_empty = 1;
local uLongf crc_table[256];
local void make_crc_table __P((void));
/*
Generate a table for a byte-wise 32-bit CRC calculation on the polynomial:
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.
Polynomials over GF(2) are represented in binary, one bit per coefficient,
with the lowest powers in the most significant bit. Then adding polynomials
is just exclusive-or, and multiplying a polynomial by x is a right shift by
one. If we call the above polynomial p, and represent a byte as the
polynomial q, also with the lowest power in the most significant bit (so the
byte 0xb1 is the polynomial x^7+x^3+x+1), then the CRC is (q*x^32) mod p,
where a mod b means the remainder after dividing a by b.
This calculation is done using the shift-register method of multiplying and
taking the remainder. The register is initialized to zero, and for each
incoming bit, x^32 is added mod p to the register if the bit is a one (where
x^32 mod p is p+x^32 = x^26+...+1), and the register is multiplied mod p by
x (which is shifting right by one and adding x^32 mod p if the bit shifted
out is a one). We start with the highest power (least significant bit) of
q and repeat for all eight bits of q.
The table is simply the CRC of all possible eight bit values. This is all
the information needed to generate CRC's on data a byte at a time for all
combinations of CRC register values and incoming bytes.
*/
local void make_crc_table()
{
uLong c;
int n, k;
uLong poly; /* polynomial exclusive-or pattern */
/* terms of polynomial defining this crc (except x^32): */
static const Byte p[] = {0,1,2,4,5,7,8,10,11,12,16,22,23,26};
/* make exclusive-or pattern from polynomial (0xedb88320L) */
poly = 0L;
for (n = 0; n < sizeof(p)/sizeof(Byte); n++)
poly |= 1L << (31 - p[n]);
for (n = 0; n < 256; n++)
{
c = (uLong)n;
for (k = 0; k < 8; k++)
c = c & 1 ? poly ^ (c >> 1) : c >> 1;
crc_table[n] = c;
}
crc_table_empty = 0;
}
#else
/* ========================================================================
* Table of CRC-32's of all single-byte values (made by make_crc_table)
*/
local const uLongf crc_table[16] = {
0x00000000L, 0x1db71064L, 0x3b6e20c8L, 0x26d930acL,
0x76dc4190L, 0x6b6b51f4L, 0x4db26158L, 0x5005713cL,
0xedb88320L, 0xf00f9344L, 0xd6d6a3e8L, 0xcb61b38cL,
0x9b64c2b0L, 0x86d3d2d4L, 0xa00ae278L, 0xbdbdf21cL
};
#endif
/* ========================================================================= */
#define DO1(buf) do { crc ^= *buf++; crc = (crc >> 4) ^ crc_table[crc & 0xf]; crc = (crc >> 4) ^ crc_table[crc & 0xf]; } while (0)
@ -88,10 +31,6 @@ uLong ZEXPORT crc32(crc, buf, len)
uInt len;
{
if (buf == Z_NULL) return 0L;
#ifdef DYNAMIC_CRC_TABLE
if (crc_table_empty)
make_crc_table();
#endif
crc = crc ^ 0xffffffffL;
while (len >= 8)
{