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Fix hash function in xdiff library

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Jim Mayering noticed that xdiff library took insanely long time
when comparing files with many identical lines.

This was because the hash function used in the library is broken
on 64-bit architectures and caused too many collisions.

http://thread.gmane.org/gmane.comp.version-control.git/28962/focus=28994

Acked-by: Davide Libenzi <davidel@xmaliserver.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
This commit is contained in:
Linus Torvalds 2006-10-16 19:58:54 -07:00 committed by Junio C Hamano
parent 6fe5b7ff6c
commit 9de0834663
1 changed files with 3 additions and 2 deletions
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5
xdiff/xmacros.h
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@ -24,14 +24,15 @@
#define XMACROS_H
#define GR_PRIME 0x9e370001UL
#define XDL_MIN(a, b) ((a) < (b) ? (a): (b))
#define XDL_MAX(a, b) ((a) > (b) ? (a): (b))
#define XDL_ABS(v) ((v) >= 0 ? (v): -(v))
#define XDL_ISDIGIT(c) ((c) >= '0' && (c) <= '9')
#define XDL_HASHLONG(v, b) (((unsigned long)(v) * GR_PRIME) >> ((CHAR_BIT * sizeof(unsigned long)) - (b)))
#define XDL_ADDBITS(v,b) ((v) + ((v) >> (b)))
#define XDL_MASKBITS(b) ((1UL << (b)) - 1)
#define XDL_HASHLONG(v,b) (XDL_ADDBITS((unsigned long)(v), b) & XDL_MASKBITS(b))
#define XDL_PTRFREE(p) do { if (p) { xdl_free(p); (p) = NULL; } } while (0)
#define XDL_LE32_PUT(p, v) \
do { \