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Added the capability to search for the terminating zero of the given string.

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Don't know what the standard says about it, but the feature seems reasonable
and other compilers handle it this way.


git-svn-id: svn://svn.cc65.org/cc65/trunk@42 b7a2c559-68d2-44c3-8de9-860c34a00d81
This commit is contained in:
cuz 2000-06-09 12:07:53 +00:00
parent 84066d5f1c
commit 4744e3602c
1 changed files with 23 additions and 16 deletions
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39
libsrc/common/strchr.s
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@ -4,9 +4,9 @@
; const char* strchr (const char* s, int c); ; const char* strchr (const char* s, int c);
; ;
.export _strchr .export _strchr
.import popax .import popax
.importzp ptr1, tmp1 .importzp ptr1, tmp1
_strchr: _strchr:
sta tmp1 ; Save c sta tmp1 ; Save c
@ -15,27 +15,34 @@ _strchr:
stx ptr1+1 stx ptr1+1
ldy #0 ldy #0
scloop: lda (ptr1),y ; get next char Loop: lda (ptr1),y ; Get next char
beq strz ; jump if end of string beq EOS ; Jump on end of string
cmp tmp1 ; found? cmp tmp1 ; Found?
beq strf ; jump if yes beq Found ; Jump if yes
iny iny
bne scloop bne Loop
inc ptr1+1 inc ptr1+1
bne scloop ; jump always bne Loop ; Branch always
; found, calculate pointer to c ; End of string. Check if we're searching for the terminating zero
strf: ldx ptr1+1 ; get high byte of pointer EOS: lda tmp1 ; Get the char we're searching for
tya ; low byte offset bne NotFound ; Jump if not searching for terminator
; Found. Calculate pointer to c.
Found: ldx ptr1+1 ; Load high byte of pointer
tya ; Low byte offset
clc clc
adc ptr1 adc ptr1
bcc str1 bcc Found1
inx inx
str1: rts Found1: rts
; not found, return zero ; Not found, return NULL
strz: tax ; return 0 NotFound:
lda #0
tax
rts rts