From 3005a8755a11e3a86472707145be362d698253c6 Mon Sep 17 00:00:00 2001
From: Ed Schouten <ed@FreeBSD.org>
Date: Thu, 26 May 2016 20:55:15 +0000
Subject: [PATCH] Let l64a() properly null terminate its result.

Though the buffer used by l64a() is initialized with null bytes,
repetetive calls may end up having trailing garbage of previous
invocations because we don't end up terminating the string.

Instead of importing NetBSD's fix, use this opportunity to simplify this
function dramatically, for example by just storing the Base64 character
set in a string. There is also no need to do the bitmasking, as we can
just use the proper integer type from <stdint.h>.

MFC after:	1 month
Differential Revision:	https://reviews.freebsd.org/D6511
---
 lib/libc/stdlib/l64a.c | 34 +++++++++++++---------------------
 1 file changed, 13 insertions(+), 21 deletions(-)

diff --git a/lib/libc/stdlib/l64a.c b/lib/libc/stdlib/l64a.c
index bc105535ed12..c281d7d823c3 100644
--- a/lib/libc/stdlib/l64a.c
+++ b/lib/libc/stdlib/l64a.c
@@ -12,18 +12,13 @@ __RCSID("$NetBSD: l64a.c,v 1.13 2003/07/26 19:24:54 salo Exp $");
 #include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");
 
+#include <stdint.h>
 #include <stdlib.h>
 
-#define	ADOT	46		/* ASCII '.' */
-#define	ASLASH	ADOT + 1	/* ASCII '/' */
-#define	A0	48		/* ASCII '0' */
-#define	AA	65		/* ASCII 'A' */
-#define	Aa	97		/* ASCII 'a' */
-
 char *
 l64a(long value)
 {
-	static char buf[8];
+	static char buf[7];
 
 	(void)l64a_r(value, buf, sizeof(buf));
 	return (buf);
@@ -32,21 +27,18 @@ l64a(long value)
 int
 l64a_r(long value, char *buffer, int buflen)
 {
-	long v;
-	int digit;
+	static const char chars[] =
+	    "./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
+	uint32_t v;
 
-	v = value & (long)0xffffffff;
-	for (; v != 0 && buflen > 1; buffer++, buflen--) {
-		digit = v & 0x3f;
-		if (digit < 2)
-			*buffer = digit + ADOT;
-		else if (digit < 12)
-			*buffer = digit + A0 - 2;
-		else if (digit < 38)
-			*buffer = digit + AA - 12;
-		else
-			*buffer = digit + Aa - 38;
+	v = value;
+	while (buflen-- > 0) {
+		if (v == 0) {
+			*buffer = '\0';
+			return (0);
+		}
+		*buffer++ = chars[v & 0x3f];
 		v >>= 6;
 	}
-	return (v == 0 ? 0 : -1);
+	return (-1);
 }