Merge pull request #192 from shattered/_463a2165

runtime: minor optimizations and bugfixes

Author: davidgiven

rt/msdos/cowgol.coh

@@ -18,6 +18,12 @@ sub AlignUp(in: intptr): (out: intptr) is
 	out := in;
 end sub;
 
+sub get_char(): (c: uint8) is
+    @asm "mov ah, 1";
+    @asm "int 0x21";
+    @asm "mov [",c,"],al";
+end sub;
+
 sub print_char(c: uint8) is
     if c == 10 then
         @asm "mov dl, 13";

rt/unixv7/cowgol.coh

@@ -1,6 +1,6 @@
 var LOMEM: [uint8];
 var HIMEM: [uint8];
- 
+
 # NB: apout ignores brk()
 sub _find_himem() is
 	@asm "mov #0087h, -(sp)"; # ret
@@ -46,27 +46,21 @@ end sub;
 
 sub MemSet(buf: [uint8], byte: uint8, len: uint16) is
 	var bufend := buf + len;
-	loop
-		if buf == bufend then
-			return;
-		end if;
+	while buf != bufend loop
 		[buf] := byte;
-		buf := buf + 1;
+		buf := @next buf;
 	end loop;
 end sub;
 
 sub print_oct_i16(value: uint16) is
-    var i: uint8 := 5;
+	var i: uint8 := 5;
 	print_char(((value >> 15) + '0') as uint8);
-    loop
-        var digit := (((value >> 12) & 7) + '0') as uint8;
-        print_char(digit);
-        value := value << 3;
-        i := i - 1;
-        if i == 0 then
-            break;
-        end if;
-    end loop;
+	value := value << 1;
+	while i > 0 loop
+		print_char(((value >> 13) + '0') as uint8);
+		value := value << 3;
+		i := i - 1;
+	end loop;
 end sub;
 
 include "common.coh";

rt/unixv7/file.coh

@@ -139,10 +139,15 @@ sub FCBClose(fcb: [FCB]): (errno: uint8) is
     FCBFlush(fcb);
 
     var fd := fcb.fd;
+    errno := 0;
     @asm "mov ", fd, ", r0";
     @asm "trap 6";
-    @asm "neg r0";
-    @asm "mov r0, ", errno;
+    @asm "adcb ", errno;
+    @asm "mov r0, ", fd;
+
+    if errno != 0 then
+        errno := fd as uint8;
+    end if;
 end sub;
 
 sub FCBExt(fcb: [FCB]): (len: uint32) is