Implement strcasestr as part of strstr

libsrc/common/strstr.s

@@ -4,11 +4,18 @@
 ; char* strstr (const char* haystack, const char* needle);
 ;
 
-        .export         _strstr
-        .import         popptr1
-        .importzp       ptr1, ptr2, ptr3, ptr4, tmp1
+        .export         _strstr, _strcasestr
+        .import         popptr1, _tolower
+        .importzp       ptr1, ptr2, ptr3, ptr4, tmp1, tmp2, tmp3
 
 _strstr:
+        ldy     #$01
+        bne     :+
+_strcasestr:
+        ldy     #$00
+:
+        sty     tmp2            ; Set case sensitivity
+
         sta     ptr2            ; Save needle
         stx     ptr2+1
         sta     ptr4            ; Setup temp copy for later
@@ -24,10 +31,19 @@ _strstr:
 ; Search for the beginning of the string (this is not an optimal search
 ; strategy [in fact, it's pretty dumb], but it's simple to implement).
 
-        sta     tmp1            ; Save start of needle
+        ldx     tmp2            ; Lowercase if needed
+        bne     :+
+        jsr     _tolower
+
+:       sta     tmp1            ; Save start of needle
 @L1:    lda     (ptr1),y        ; Get next char from haystack
         beq     @NotFound       ; Jump if end
-        cmp     tmp1            ; Start of needle found?
+
+        ldx     tmp2            ; Lowercase if needed
+        bne     :+
+        jsr     _tolower
+
+:       cmp     tmp1            ; Start of needle found?
         beq     @L2             ; Jump if so
         iny                     ; Next char
         bne     @L1
@@ -43,7 +59,7 @@ _strstr:
         bcc     @L3
         inc     ptr1+1
 
-; ptr1 points to the start of needle now. Setup temporary pointers for the
+; ptr1 points to the start of needle in haystack now. Setup temporary pointers for the
 ; search. The low byte of ptr4 is already set.
 
 @L3:    sta     ptr3
@@ -57,7 +73,19 @@ _strstr:
 
 @L4:    lda     (ptr4),y        ; Get char from needle
         beq     @Found          ; Jump if end of needle (-> found)
-        cmp     (ptr3),y        ; Compare with haystack
+
+        ldx     tmp2            ; Lowercase if needed
+        bne     :+
+        jsr     _tolower
+:       sta     tmp3
+
+        lda     (ptr3),y        ; Compare with haystack
+
+        ldx     tmp2            ; Lowercase if needed
+        bne     :+
+        jsr     _tolower
+
+:       cmp     tmp3
         bne     @L5             ; Jump if not equal
         iny                     ; Next char
         bne     @L4
@@ -82,14 +110,3 @@ _strstr:
         lda     #$00            ; return NULL
         tax
         rts
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