[libc] Make sleep() interruptible

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/core/timer.c

@@ -24,6 +24,10 @@
 FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 
 #include <unistd.h>
+#include <ipxe/process.h>
+#include <ipxe/console.h>
+#include <ipxe/keys.h>
+#include <ipxe/nap.h>
 
 /**
  * Delay for a fixed number of milliseconds
@@ -36,12 +40,24 @@ void mdelay ( unsigned long msecs ) {
 }
 
 /**
- * Delay for a fixed number of seconds
+ * Sleep (interruptibly) for a fixed number of seconds
  *
  * @v secs		Number of seconds for which to delay
+ * @ret secs		Number of seconds remaining, if interrupted
  */
 unsigned int sleep ( unsigned int secs ) {
-	while ( secs-- )
-		mdelay ( 1000 );
+	unsigned long start = currticks();
+	unsigned long now;
+
+	for ( ; secs ; secs-- ) {
+		while ( ( ( now = currticks() ) - start ) < TICKS_PER_SEC ) {
+			step();
+			if ( iskey() && ( getchar() == CTRL_C ) )
+				return secs;
+			cpu_nap();
+		}
+		start = now;
+	}
+
 	return 0;
 }