Initial Agat support

libsrc/agat/write.s

@@ -0,0 +1,50 @@
+;
+; Oleg A. Odintsov, Moscow, 2024
+;
+; int __fastcall__ write (int fd, const void* buf, unsigned count);
+;
+
+        .export         _write
+        .import         popax, popptr1
+        .import         COUT
+
+        .include        "zeropage.inc"
+
+_write:
+        sta     ptr2
+        stx     ptr2+1
+        jsr     popptr1
+        jsr     popax
+
+        ; Check for zero count
+        ora     ptr2
+        beq     done
+
+        ; Get char from buf
+next:   ldy     #$00
+        lda     (ptr1),y
+
+        ; Replace '\n' with '\r'
+        cmp     #$0A
+        bne     output
+        lda     #$8D
+
+        ; Set hi bit and write to device
+output:
+        jsr     COUT            ; Preserves X and Y
+
+        ; Increment pointer
+        inc     ptr1
+        bne     :+
+        inc     ptr1+1
+
+        ; Decrement count
+:       dec     ptr2
+        bne     next
+        dec     ptr2+1
+        bpl     next
+
+        ; Return success
+done:   lda     #$00
+        rts
+