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

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

diff --git a/libsrc/common/strchr.s b/libsrc/common/strchr.s
index 7a5c767d0836fe4efcbd61f62756846bd9a6fa09..d1761b905fc549afd2b86cf43277f895071a9329 100644 (file)
--- a/libsrc/common/strchr.s
+++ b/libsrc/common/strchr.s
@@ -4,9 +4,9 @@
 ; const char* strchr (const char* s, int c);
 ;
 
-       .export         _strchr
-       .import         popax
-       .importzp       ptr1, tmp1
+       .export         _strchr
+       .import         popax
+       .importzp       ptr1, tmp1
 
 _strchr:
                sta     tmp1            ; Save c
@@ -15,27 +15,34 @@ _strchr:
                stx     ptr1+1
                ldy     #0
 
-scloop:        lda     (ptr1),y        ; get next char
-               beq     strz            ; jump if end of string
-               cmp     tmp1            ; found?
-               beq     strf            ; jump if yes
+Loop:  lda     (ptr1),y        ; Get next char
+       beq     EOS             ; Jump on end of string
+       cmp     tmp1            ; Found?
+       beq     Found           ; Jump if yes
                iny
-               bne     scloop
+               bne     Loop
                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
-               tya                     ; low byte offset
+EOS:   lda     tmp1            ; Get the char we're searching for
+       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
                adc     ptr1
-               bcc     str1
+               bcc     Found1
                inx
-str1:          rts
+Found1:        rts
 
-; not found, return zero
+; Not found, return NULL
 
-strz:  tax                     ; return 0
+NotFound:
+       lda     #0
+       tax
        rts