From 99ca35977ce22dfd14e63927ce974251b54f5cfb Mon Sep 17 00:00:00 2001
From: John Marshall <jm18@sanger.ac.uk>
Date: Wed, 24 Jul 2013 14:08:25 +0100
Subject: [PATCH] Only canonicalise if there is room, and add docs

We could increment SIZE to ensure there would be room, but that would
disadvantage people using kstrings for binary data in power-of-2-sized
blocks.  Instead document that SIZE=KS.l+1 will ensure NUL-termination.

This fixes a bug in the previous version when the l<m invariant does not
hold (kputc_()/etc and manual manipulation only maintain the weaker l<=m);
hattip Rob Davies.
---
 kstring.h | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/kstring.h b/kstring.h
index 4c803b8..360a598 100644
--- a/kstring.h
+++ b/kstring.h
@@ -78,6 +78,9 @@ extern "C" {
 }
 #endif
 
+/* Ensures that the string has space for at least SIZE bytes, and ensures that
+ * it is NUL-terminated if there is room.  Thus ks_resize(&s,s.l+1) can be used
+ * to make sure that a kstring_t is both allocated and NUL-terminated.  */
 static inline int ks_resize(kstring_t *s, size_t size)
 {
 	if (s->m < size) {
@@ -89,7 +92,7 @@ static inline int ks_resize(kstring_t *s, size_t size)
 		else
 			return -1;
 	}
-	s->s[s->l] = '\0';
+	if (s->l < s->m) s->s[s->l] = '\0';
 	return 0;
 }
 
-- 
2.47.3