a

libc/dirfstat.c

@@ -0,0 +1,37 @@
+#include <u.h>
+#include <libc.h>
+#include <fcall.h>
+
+enum
+{
+	DIRSIZE	= STATFIXLEN + 16 * 4		/* enough for encoded stat buf + some reasonable strings */
+};
+
+Dir*
+dirfstat(int fd)
+{
+	Dir *d;
+	uchar *buf;
+	int n, nd, i;
+
+	nd = DIRSIZE;
+	for(i=0; i<2; i++){	/* should work by the second try */
+		d = malloc(sizeof(Dir) + BIT16SZ + nd);
+		if(d == nil)
+			return nil;
+		buf = (uchar*)&d[1];
+		n = fstat(fd, buf, BIT16SZ+nd);
+		if(n < BIT16SZ){
+			free(d);
+			return nil;
+		}
+		nd = GBIT16(buf);	/* upper bound on size of Dir + strings */
+		if(nd <= n){
+			convM2D(buf, n, d, (char*)&d[1]);
+			return d;
+		}
+		/* else sizeof(Dir)+BIT16SZ+nd is plenty */
+		free(d);
+	}
+	return nil;
+}