[PATCH] fast AND correct strncpy

This is Erik Andersen's excellent strncpy.
It works like magic. That "if" isn't a jump;
gcc uses a few integer instructions to wipe
out all jumps except for the loop itself and
the function call/return.

This has been exhaustively tested against glibc.

The existing code has 5 extra branches and
is over twice as large. (my gcc, etc.)

lib/string.c

@@ -87,13 +87,12 @@ char * strncpy(char * dest,const char *src,size_t count)
 {
 	char *tmp = dest;
 
-	while (count && (*dest++ = *src++) != '\0')
-		count--;
-	while (count > 1) {
-		*dest++ = 0;
+	while (count) {
+		if ((*tmp = *src) != 0) src++;
+		tmp++;
 		count--;
 	}
-	return tmp;
+	return dest;
 }
 #endif