unit tests for src/common/buffer.{cc,h}

Implement unit tests covering most lines of code ( > 92% ) and all
methods as show by the output of make check-coverage :
http://dachary.org/wp-uploads/2013/03/ceph-lcov/ .

The following static constructors are implemented by opaque classes
defined in buffer.cc ( buffer::raw_char, buffer::raw_posix_aligned
etc. ). Testing the implementation of these classes is done by
variations of the calls to the static constructors.

    copy(const char *c, unsigned len);
    create(unsigned len);
    claim_char(unsigned len, char *buf);
    create_malloc(unsigned len);
    claim_malloc(unsigned len, char *buf);
    create_static(unsigned len, char *buf);
    create_page_aligned(unsigned len);

The raw_mmap_pages class cannot be tested because it is commented out in
raw_posix_aligned. The raw_hack_aligned class is only tested under Cygwin.
The raw_posix_aligned class is not tested under Cygwin.

The unittest_bufferlist.sh script calls unittest_bufferlist with the
CEPH_BUFFER_TRACK=true environment variable to enable the code
tracking the memory usage. It cannot be done within the bufferlist.cc
file itself because it relies on the initialization of a global
variable  ( buffer_track_alloc ).

When raw_posix_aligned is called on DARWIN, the data is not aligned
on CEPH_PAGE_SIZE because it calls valloc(size) which is the equivalent of
memalign(sysconf(_SC_PAGESIZE),size) and not memalign(CEPH_PAGE_SIZE,size).
For this reason the alignment test is de-activated on DARWIN.

The tests are grouped in

TEST(BufferPtr, ... ) for buffer::ptr
TEST(BufferListIterator, ...) for buffer::list::iterator
TEST(BufferList, ...) for buffer::list
TEST(BufferHash, ...) for buffer::hash

and each method ( and all variations of the prototype ) are
included into a single TEST() function.

Although most aspects of the methods are tested, including exceptions
and border cases, inconsistencies are not highlighted . For
instance

    buffer::list::iterator i;
    i.advance(1);

would dereference a buffer::raw NULL pointer although

    buffer::ptr p;
    p.wasted()

asserts instead of dereferencing the buffer::raw NULL pointer. It
would be better to always assert in case a NULL pointer is about to be
used. But this is a minor inconsistency that is probably not worth a
test.

The following buffer::list methods

    ssize_t read_fd(int fd, size_t len);
    int write_fd(int fd) const;

are not fully tested because the border cases cannot be reliably
reproduced. Going thru a pointer indirection when calling the ::writev
or safe_read functions would allow the test to create mockups to synthetize
the conditions for border cases.

tracker.ceph.com/issues/4066 refs #4066

Signed-off-by: Loic Dachary <loic@dachary.org>

src/Makefile.am

@@ -19,7 +19,8 @@ EXTRA_DIST = \
 	libs3/libs3.spec \
 	libs3/mswin \
 	libs3/src \
-	libs3/test
+	libs3/test \
+	unittest_bufferlist.sh
 
 CLEANFILES =
 bin_PROGRAMS =
@@ -38,7 +39,7 @@ check_PROGRAMS =
 # tests to actually run on "make check"; if you need extra, non-test,
 # executables built, you need to replace this with manual assignments
 # target by target
-TESTS = $(check_PROGRAMS)
+TESTS = $(check_PROGRAMS) unittest_bufferlist.sh
 
 check-local:
 	$(srcdir)/test/encoding/check-generated.sh

src/unittest_bufferlist.sh

@@ -0,0 +1,19 @@
+#!/bin/bash
+#
+# Ceph - scalable distributed file system
+#
+# Copyright (C) 2013 Cloudwatt <libre.licensing@cloudwatt.com>
+#
+# Author: Loic Dachary <loic@dachary.org>
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU Library Public License as published by
+# the Free Software Foundation; either version 2, or (at your option)
+# any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Library Public License for more details.
+#
+CEPH_BUFFER_TRACK=true ./unittest_bufferlist