gnu: libevent@2.0: Add fix from upstream.

This fix was cherry-picked by Mozilla from upstream libevent-2.1 to its
bundled copy of libevent-2.0.21 in mozilla-esr45.

* gnu/packages/patches/libevent-2.0-evbuffer-add-use-last-with-datap.patch:
New file.
* gnu/local.mk (dist_patch_DATA): Add it.
* gnu/packages/libevent.scm (libevent-2.0)[source][patches]: Add it.

1 files changed, 38 insertions, 0 deletions

diff --git a/gnu/packages/patches/libevent-2.0-evbuffer-add-use-last-with-datap.patch b/gnu/packages/patches/libevent-2.0-evbuffer-add-use-last-with-datap.patch
new file mode 100644
index 0000000000..0253700bf6
--- /dev/null
+++ b/gnu/packages/patches/libevent-2.0-evbuffer-add-use-last-with-datap.patch
@@ -0,0 +1,38 @@
+From a8769ef12d7e223e33fc47bed03fba2bfa2f3536 Mon Sep 17 00:00:00 2001
+From: Marcus Sundberg <marcus@marcussundberg.com>
+Date: Sat, 26 Mar 2016 20:11:43 +0100
+Subject: [PATCH] evbuffer_add: Use last_with_datap if set, not last.
+
+evbuffer_add() would always put data in the last chain, even if there
+was available space in a previous chain, and in doing so it also
+failed to update last_with_datap, causing subsequent calls to other
+functions that do look at last_with_datap to add data in the middle
+of the evbuffer instead of at the end.
+
+Fixes the evbuffer_add() part of issue #335, and the evbuffer/add2 and
+evbuffer/add3 tests, and also prevents wasting space available in the
+chain pointed to by last_with_datap.
+---
+ buffer.c | 6 +++++-
+ 1 file changed, 5 insertions(+), 1 deletion(-)
+
+diff --git a/buffer.c b/buffer.c
+index 7cca0e8a..f378b731 100644
+--- a/buffer.c
++++ b/buffer.c
+@@ -1732,7 +1732,11 @@ evbuffer_add(struct evbuffer *buf, const void *data_in, size_t datlen)
+ 		goto done;
+ 	}
+ 
+-	chain = buf->last;
++	if (*buf->last_with_datap == NULL) {
++		chain = buf->last;
++	} else {
++		chain = *buf->last_with_datap;
++	}
+ 
+ 	/* If there are no chains allocated for this buffer, allocate one
+ 	 * big enough to hold all the data. */
+-- 
+2.12.0
+