Merge pull request #2769 from colinleroy/add-strndup

Add strndup
2025-07-04 17:01:28 +02:00
parent 14eae07a8c 90e1ac374b
commit fd973cd544
6 changed files with 199 additions and 0 deletions
--- a/libsrc/common/strndup.s
+++ b/libsrc/common/strndup.s
@@ -0,0 +1,56 @@
+;
+; Colin Leroy-Mira, 03.07.2025
+;
+; char* __fastcall__ strndup (const char* S, size_t maxlen);
+;
+
+        .importzp       ptr4, c_sp
+        .import         _strdup, _strlen, pushax, popax, _realloc
+
+        .export         _strndup
+
+_strndup:
+        sta     maxlen        ; Remember maxlen
+        stx     maxlen+1
+
+        jsr     popax         ; Duplicate string
+        jsr     _strdup
+        jsr     pushax        ; Remember result
+
+        jsr     _strlen       ; Check length,
+        cpx     maxlen+1
+        bcc     out           ; Return directly if < maxlen
+        bne     :+
+        cmp     maxlen
+        bcc     out
+
+:       ldy     #$00          ; Otherwise, point to end of string,
+        lda     maxlen
+        clc
+        adc     (c_sp),y
+        sta     ptr4
+        lda     maxlen+1
+        iny
+        adc     (c_sp),y
+        sta     ptr4+1
+
+        dey                   ; Cut it short,
+        tya
+        sta     (ptr4),y
+
+        ldx     maxlen+1      ; And finally, realloc to maxlen+1
+        ldy     maxlen
+        iny
+        tya
+        bne     :+
+        inx
+:       jsr     _realloc      ; TOS still contains result
+                              ; We consider realloc will not fail,
+                              ; as the block shrinks.
+        jsr     pushax        ; push/pop for size optimisation
+out:
+        jmp     popax
+
+        .bss
+
+maxlen: .res 2