Add signal() and raise()

git-svn-id: svn://svn.cc65.org/cc65/trunk@2017 b7a2c559-68d2-44c3-8de9-860c34a00d81

libsrc/common/signal.s

@@ -0,0 +1,68 @@
+;
+; Ullrich von Bassewitz, 2002-12-16
+;
+; __sigfunc __fastcall__ signal (int sig, __sigfunc func);
+;
+
+	.import		popax
+	.importzp	ptr1
+
+        .include        "signal.inc"
+        .include        "errno.inc"
+
+
+; Default signal functions: The standard specifies explicitly that the values
+; for SIG_IGN and SIG_DFL must be distinct, so we make them so by using both
+; rts exits we have. This works because signal functions are __fastcall__, so
+; we don't have arguments on the stack.
+
+
+;----------------------------------------------------------------------------
+; __sigfunc __fastcall__ signal (int sig, __sigfunc func);
+
+
+_signal:
+        sta     ptr1
+        stx     ptr1+1          ; Remember func
+
+        jsr     popax           ; Get sig
+
+        cpx     #0
+        bne     invalidsig
+        cmp     #SIGCOUNT
+        bcs     invalidsig
+
+; Signal number is valid. Replace the pointer in the table saving the old
+; value temporarily on the stack.
+
+        asl     a               ; Prepare for word access
+        tax
+
+        lda     sigtable,x
+        pha
+        lda     ptr1
+        sta     sigtable,x
+        lda     sigtable+1,x
+        pha
+        lda     ptr1+1
+        sta     sigtable+1,x
+
+; Get the old value from the stack and return it
+
+        pla
+        tax
+        pla
+__sig_ign:
+        rts
+
+; Error entry: We use our knowledge that SIG_ERR is zero here to save a byte
+
+invalidsig:
+        lda     #<EINVAL
+        sta     __errno
+        lda     #>EINVAL        ; A = 0
+        sta     __errno+1
+        tax                     ; A/X = 0
+__sig_dfl:
+        rts
+