[PATCH] buffer::ptr::cmp only compares up to the smallest length

[Loic Dachary <loic@dachary.org>]

When running

  bufferptr a("A", 1);
  bufferptr ab("AB", 2);
  a.cmp(ab);

it returned zero because cmp only compared up to the length of the
smallest buffer. The tests comparing the length of the buffers are
moved before the memcmp comparing the actual content of the buffers.

http://tracker.ceph.com/issues/4170 refs #4170

Signed-off-by: Loic Dachary <loic@dachary.org>
---
 src/common/buffer.cc   |    8 +-------
 src/test/bufferlist.cc |   14 ++++++++++++++
 2 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/src/common/buffer.cc b/src/common/buffer.cc
index e10d6c9..5a88849 100644
--- a/src/common/buffer.cc
+++ b/src/common/buffer.cc
@@ -368,17 +368,11 @@ bool buffer_track_alloc = get_env_bool("CEPH_BUFFER_TRACK");
 
   int buffer::ptr::cmp(const ptr& o)
   {
-    int l = _len < o._len ? _len : o._len;
-    if (l) {
-      int r = memcmp(c_str(), o.c_str(), l);
-      if (!r)
-	return r;
-    }
     if (_len < o._len)
       return -1;
     if (_len > o._len)
       return 1;
-    return 0;
+    return memcmp(c_str(), o.c_str(), _len);
   }
 
   bool buffer::ptr::is_zero() const
diff --git a/src/test/bufferlist.cc b/src/test/bufferlist.cc
index 71c2e79..aac41c6 100644
--- a/src/test/bufferlist.cc
+++ b/src/test/bufferlist.cc
@@ -9,6 +9,20 @@
 
 #define MAX_TEST 1000000
 
+TEST(BufferPtr, cmp) {
+  bufferptr empty;
+  bufferptr a("A", 1);
+  bufferptr ab("AB", 2);
+  bufferptr af("AF", 2);
+  EXPECT_GE(-1, empty.cmp(a));
+  EXPECT_LE(1, a.cmp(empty));
+  EXPECT_GE(-1, a.cmp(ab));
+  EXPECT_LE(1, ab.cmp(a));
+  EXPECT_EQ(0, ab.cmp(ab));
+  EXPECT_GE(-1, ab.cmp(af));
+  EXPECT_LE(1, af.cmp(ab));
+}
+
 TEST(BufferList, zero) {
   //
   // void zero()
-- 
1.7.10.4