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Change comments about algorithms, 99.6% for random data isn't 'rare' in my book! 

(The 'rare' case is any byte values 0x80-0xff.)
This commit is contained in:
dsl 2009-07-11 08:48:51 +00:00
parent 9a7f03a6bb
commit 5acd65fcb7
1 changed files with 5 additions and 5 deletions
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10
common/lib/libc/arch/x86_64/string/strlen.S
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@ -6,7 +6,7 @@
#include <machine/asm.h> #include <machine/asm.h>
#if defined(LIBC_SCCS) #if defined(LIBC_SCCS)
RCSID("$NetBSD: strlen.S,v 1.1 2005/12/20 19:28:51 christos Exp $") RCSID("$NetBSD: strlen.S,v 1.2 2009/07/11 08:48:51 dsl Exp $")
#endif #endif
ENTRY(strlen) ENTRY(strlen)
@ -74,9 +74,9 @@ ENTRY(strlen)
* (3) ((x - 0x01....01) & 0x80....80) * (3) ((x - 0x01....01) & 0x80....80)
* *
* always evaluates to a non-zero value if any of the bytes in * always evaluates to a non-zero value if any of the bytes in
* the original word is zero. However, in rare cases, it also * the original word is zero or has the top bit set.
* evaluates to a non-zero value when none of the bytes in the * For strings that are likely to only contain 7-bit ascii these
* original word is zero. * false positives will be rare.
* *
* To account for possible false positives, each byte of the * To account for possible false positives, each byte of the
* original word must be checked when the expression evaluates to * original word must be checked when the expression evaluates to
@ -110,7 +110,7 @@ ENTRY(strlen)
je .Lloop je .Lloop
/* /*
* In rare cases, the above loop may exit prematurely. We must * For bytes 0x80-0xff the above loop will exit prematurely. We must
* return to the loop if none of the bytes in the word equal 0. * return to the loop if none of the bytes in the word equal 0.
*/ */
cmpb $0,-8(%rax) /* 1st byte == 0? */ cmpb $0,-8(%rax) /* 1st byte == 0? */