Fix strnvis(): don't truncate unnecessarily, set the return value correctly

if we had to truncate, and don't NUL-terminate if size == 0.

2 files changed, 31 insertions, 17 deletions

diff --git a/lib/libc/gen/vis.3 b/lib/libc/gen/vis.3
index 58e6d94f218..89487c7952e 100644
--- a/lib/libc/gen/vis.3
+++ b/lib/libc/gen/vis.3
@@ -1,4 +1,4 @@
-.\"	$OpenBSD: vis.3,v 1.15 2001/11/09 19:34:46 aaron Exp $
+.\"	$OpenBSD: vis.3,v 1.16 2002/07/01 07:48:50 pjanzen Exp $
 .\"
 .\" Copyright (c) 1989, 1991, 1993
 .\"	The Regents of the University of California.  All rights reserved.
@@ -45,11 +45,11 @@
 .Ft char *
 .Fn vis "char *dst" "char c" "int flag" "char nextc"
 .Ft int
-.Fn strvis "char *dst" "char *src" "int flag"
+.Fn strvis "char *dst" "const char *src" "int flag"
 .Ft int
-.Fn strnvis "char *dst" "char *src" "size_t size" "int flag"
+.Fn strnvis "char *dst" "const char *src" "size_t size" "int flag"
 .Ft int
-.Fn strvisx "char *dst" "char *src" "size_t len" "int flag"
+.Fn strvisx "char *dst" "const char *src" "size_t len" "int flag"
 .Sh DESCRIPTION
 The
 .Fn vis
@@ -111,7 +111,14 @@ characters from
 (this
 is useful for encoding a block of data that may contain NULs).
 All three forms NUL terminate
-.Fa dst .
+.Fa dst ,
+except for
+.Fn strnvis
+when
+.Fa size
+is zero, in which case
+.Fa dst
+is not touched.
 For
 .Fn strvis
 and
diff --git a/lib/libc/gen/vis.c b/lib/libc/gen/vis.c
index 894366e8cc1..76c44acebfd 100644
--- a/lib/libc/gen/vis.c
+++ b/lib/libc/gen/vis.c
@@ -32,7 +32,7 @@
  */
 
 #if defined(LIBC_SCCS) && !defined(lint)
-static char rcsid[] = "$OpenBSD: vis.c,v 1.8 2002/02/19 19:39:36 millert Exp $";
+static char rcsid[] = "$OpenBSD: vis.c,v 1.9 2002/07/01 07:48:50 pjanzen Exp $";
 #endif /* LIBC_SCCS and not lint */
 
 #include <sys/types.h>
@@ -168,16 +168,20 @@ strvis(dst, src, flag)
 
 int
 strnvis(dst, src, siz, flag)
-	register char *dst;
-	register const char *src;
+	char *dst;
+	const char *src;
 	size_t siz;
 	int flag;
 {
-	register char c;
+	char c;
 	char *start, *end;
+	char tbuf[5];
+	int  i;
 
+	i = 0;
 	for (start = dst, end = start + siz - 1; (c = *src) && dst < end; ) {
 		if (isvisible(c)) {
+			i = 1;
 			*dst++ = c;
 			if (c == '\\' && (flag & VIS_NOSLASH) == 0) {
 				/* need space for the extra '\\' */
@@ -185,22 +189,25 @@ strnvis(dst, src, siz, flag)
 					*dst++ = '\\';
 				else {
 					dst--;
+					i = 2;
 					break;
 				}
 			}
 			src++;
 		} else {
-			/* vis(3) requires up to 4 chars */
-			if (dst + 3 < end)
-				dst = vis(dst, c, flag, *++src);
-			else
+			i = vis(tbuf, c, flag, *++src) - tbuf;
+			if (dst + i <= end) {
+				memcpy(dst, tbuf, i);
+				dst += i;
+			} else {
+				src--;
 				break;
+			}
 		}
 	}
-	*dst = '\0';
-	if (dst >= end) {
-		char tbuf[5];
-
+	if (siz > 0)
+		*dst = '\0';
+	if (dst + i > end) {
 		/* adjust return value for truncation */
 		while ((c = *src))
 			dst += vis(tbuf, c, flag, *++src) - tbuf;