[glib] tests: additional test for g_bytes_new_from_bytes()

[Christian Hergert <chergert src gnome org>]

commit 47b78e6d83e82e18218b6beb5fb127b08e3bc79a
Author: Christian Hergert <chergert redhat com>
Date:   Mon Jan 22 15:35:07 2018 -0800

    tests: additional test for g_bytes_new_from_bytes()
    
    This adds two new tests for g_bytes_new_from_bytes().
    
    One test ensures that when creating a new GBytes that is a slice of
    the entire base bytes, we just return the base bytes with it's reference
    count incremented by one.
    
    The other test ensures that when performing sub-slices of GBytes, for
    which the parent GBytes also references a GBytes, that we skip the
    intermediate GBytes and reference the base GBytes. Additional testing
    of the internal state of the GBytes structure is performed to prove
    the correctness of the implementation.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=792780

 glib/gbytes.c      |    1 +
 glib/tests/bytes.c |   65 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 66 insertions(+), 0 deletions(-)
---
diff --git a/glib/gbytes.c b/glib/gbytes.c
index 153d5f1..3b14a51 100644
--- a/glib/gbytes.c
+++ b/glib/gbytes.c
@@ -64,6 +64,7 @@
  * Since: 2.32
  **/
 
+/* Keep in sync with glib/tests/bytes.c */
 struct _GBytes
 {
   gconstpointer data;  /* may be NULL iff (size == 0) */
diff --git a/glib/tests/bytes.c b/glib/tests/bytes.c
index a436eae..5ea5c2b 100644
--- a/glib/tests/bytes.c
+++ b/glib/tests/bytes.c
@@ -17,6 +17,16 @@
 #include <string.h>
 #include "glib.h"
 
+/* Keep in sync with glib/gbytes.c */
+struct _GBytes
+{
+  gconstpointer data;
+  gsize size;
+  gint ref_count;
+  GDestroyNotify free_func;
+  gpointer user_data;
+};
+
 static const gchar *NYAN = "nyannyan";
 static const gsize N_NYAN = 8;
 
@@ -90,6 +100,59 @@ test_new_from_bytes (void)
   g_bytes_unref (sub);
 }
 
+/* Verify that creating slices of GBytes reference the top-most bytes
+ * at the correct offset. Ensure that intermediate GBytes are not referenced.
+ */
+static void
+test_new_from_bytes_slice (void)
+{
+  GBytes *bytes = g_bytes_new_static ("Some stupid data", strlen ("Some stupid data") + 1);
+  GBytes *bytes1 = g_bytes_new_from_bytes (bytes, 4, 13);
+  GBytes *bytes2 = g_bytes_new_from_bytes (bytes1, 1, 12);
+  GBytes *bytes3 = g_bytes_new_from_bytes (bytes2, 0, 6);
+
+  g_assert_cmpint (bytes->ref_count, ==, 4);
+  g_assert_cmpint (bytes1->ref_count, ==, 1);
+  g_assert_cmpint (bytes2->ref_count, ==, 1);
+  g_assert_cmpint (bytes3->ref_count, ==, 1);
+
+  g_assert_null (bytes->user_data);
+  g_assert (bytes1->user_data == bytes);
+  g_assert (bytes2->user_data == bytes);
+  g_assert (bytes3->user_data == bytes);
+
+  g_assert_cmpint (17, ==, g_bytes_get_size (bytes));
+  g_assert_cmpint (13, ==, g_bytes_get_size (bytes1));
+  g_assert_cmpint (12, ==, g_bytes_get_size (bytes2));
+  g_assert_cmpint (6, ==, g_bytes_get_size (bytes3));
+
+  g_assert_cmpint (0, ==, strncmp ("Some stupid data", (gchar *)bytes->data, 17));
+  g_assert_cmpint (0, ==, strncmp (" stupid data", (gchar *)bytes1->data, 13));
+  g_assert_cmpint (0, ==, strncmp ("stupid data", (gchar *)bytes2->data, 12));
+  g_assert_cmpint (0, ==, strncmp ("stupid", (gchar *)bytes3->data, 6));
+
+  g_bytes_unref (bytes);
+  g_bytes_unref (bytes1);
+  g_bytes_unref (bytes2);
+  g_bytes_unref (bytes3);
+}
+
+/* Ensure that referencing an entire GBytes just returns the same bytes
+ * instance (with incremented reference count) instead of a new instance.
+ */
+static void
+test_new_from_bytes_shared_ref (void)
+{
+  GBytes *bytes = g_bytes_new_static ("Some data", strlen ("Some data") + 1);
+  GBytes *other = g_bytes_new_from_bytes (bytes, 0, g_bytes_get_size (bytes));
+
+  g_assert (bytes == other);
+  g_assert_cmpint (bytes->ref_count, ==, 2);
+
+  g_bytes_unref (bytes);
+  g_bytes_unref (other);
+}
+
 static void
 on_destroy_increment (gpointer data)
 {
@@ -336,6 +399,8 @@ main (int argc, char *argv[])
   g_test_add_func ("/bytes/new-static", test_new_static);
   g_test_add_func ("/bytes/new-with-free-func", test_new_with_free_func);
   g_test_add_func ("/bytes/new-from-bytes", test_new_from_bytes);
+  g_test_add_func ("/bytes/new-from-bytes-slice", test_new_from_bytes_slice);
+  g_test_add_func ("/bytes/new-from-bytes-shared-ref", test_new_from_bytes_shared_ref);
   g_test_add_func ("/bytes/hash", test_hash);
   g_test_add_func ("/bytes/equal", test_equal);
   g_test_add_func ("/bytes/compare", test_compare);