lib/repo: Add ostree_repo_hash() and tests

Add a hash function for OstreeRepo instances, which relies on the repo
being open, and hence being able to hash the device and inode of its
root directory.

Add unit tests for this and ostree_repo_equal().

Signed-off-by: Philip Withnall <withnall@endlessm.com>

https://github.com/ostreedev/ostree/issues/1191

Closes: #1205
Approved by: cgwalters

Makefile-tests.am

@@ -212,7 +212,7 @@ endif
 _installed_or_uninstalled_test_programs = tests/test-varint tests/test-ot-unix-utils tests/test-bsdiff tests/test-mutable-tree \
 	tests/test-keyfile-utils tests/test-ot-opt-utils tests/test-ot-tool-util \
 	tests/test-gpg-verify-result tests/test-checksum tests/test-lzma tests/test-rollsum \
-	tests/test-basic-c tests/test-sysroot-c tests/test-pull-c
+	tests/test-basic-c tests/test-sysroot-c tests/test-pull-c tests/test-repo
 
 if ENABLE_EXPERIMENTAL_API
 test_programs += \
@@ -282,6 +282,9 @@ tests_test_sysroot_c_LDADD = $(TESTS_LDADD)
 tests_test_pull_c_CFLAGS = $(TESTS_CFLAGS)
 tests_test_pull_c_LDADD = $(TESTS_LDADD)
 
+tests_test_repo_CFLAGS = $(TESTS_CFLAGS)
+tests_test_repo_LDADD = $(TESTS_LDADD)
+
 tests_test_ot_unix_utils_CFLAGS = $(TESTS_CFLAGS)
 tests_test_ot_unix_utils_LDADD = $(TESTS_LDADD)
 

apidoc/ostree-sections.txt

@@ -287,6 +287,7 @@ ostree_repo_get_path
 ostree_repo_get_mode
 ostree_repo_get_config
 ostree_repo_get_dfd
+ostree_repo_hash
 ostree_repo_equal
 ostree_repo_copy_config
 ostree_repo_remote_add

src/libostree/libostree-devel.sym

@@ -21,6 +21,7 @@
 LIBOSTREE_2017.12 {
 global:
   ostree_repo_equal;
+  ostree_repo_hash;
 } LIBOSTREE_2017.11;
 
 

src/libostree/ostree-repo.c

@@ -2609,6 +2609,36 @@ ostree_repo_get_dfd (OstreeRepo  *self)
   return self->repo_dir_fd;
 }
 
+/**
+ * ostree_repo_hash:
+ * @self: an #OstreeRepo
+ *
+ * Calculate a hash value for the given open repository, suitable for use when
+ * putting it into a hash table. It is an error to call this on an #OstreeRepo
+ * which is not yet open, as a persistent hash value cannot be calculated until
+ * the repository is open and the inode of its root directory has been loaded.
+ *
+ * This function does no I/O.
+ *
+ * Returns: hash value for the #OstreeRepo
+ * Since: 2017.12
+ */
+guint
+ostree_repo_hash (OstreeRepo *self)
+{
+  g_return_val_if_fail (OSTREE_IS_REPO (self), 0);
+
+  /* We cannot hash non-open repositories, since their hash value would change
+   * once they’re opened, resulting in false lookup misses and the inability to
+   * remove them from a hash table. */
+  g_assert (self->repo_dir_fd >= 0);
+
+  /* device and inode numbers are distributed fairly uniformly, so we can’t
+   * do much better than just combining them. No need to rehash to even out
+   * the distribution. */
+  return (self->device ^ self->inode);
+}
+
 /**
  * ostree_repo_equal:
  * @a: an #OstreeRepo

src/libostree/ostree-repo.h

@@ -123,6 +123,8 @@ GFile *       ostree_repo_get_path (OstreeRepo  *self);
 _OSTREE_PUBLIC
 int           ostree_repo_get_dfd (OstreeRepo  *self);
 
+_OSTREE_PUBLIC
+guint         ostree_repo_hash (OstreeRepo *self);
 _OSTREE_PUBLIC
 gboolean      ostree_repo_equal (OstreeRepo *a,
                                  OstreeRepo *b);

tests/.gitignore

@@ -15,6 +15,7 @@ test-mutable-tree
 test-ot-opt-utils
 test-ot-tool-util
 test-ot-unix-utils
+test-repo
 test-repo-finder-avahi
 test-repo-finder-config
 test-repo-finder-mount

tests/test-repo.c

@@ -0,0 +1,168 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*-
+ *
+ * Copyright © 2017 Endless Mobile, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ *
+ * Authors:
+ *  - Philip Withnall <withnall@endlessm.com>
+ */
+
+#include "config.h"
+
+#include <gio/gio.h>
+#include <glib.h>
+#include <glib-object.h>
+#include <libglnx.h>
+#include <locale.h>
+
+#include "ostree-autocleanups.h"
+#include "ostree-types.h"
+
+/* Test fixture. Creates a temporary directory. */
+typedef struct
+{
+  GLnxTmpDir tmpdir;  /* (owned) */
+} Fixture;
+
+static void
+setup (Fixture       *fixture,
+       gconstpointer  test_data)
+{
+  g_autoptr(GError) error = NULL;
+
+  (void) glnx_mkdtemp ("test-repo-XXXXXX", 0700, &fixture->tmpdir, &error);
+  g_assert_no_error (error);
+
+  g_test_message ("Using temporary directory: %s", fixture->tmpdir.path);
+}
+
+static void
+teardown (Fixture       *fixture,
+          gconstpointer  test_data)
+{
+  /* Recursively remove the temporary directory. */
+  (void) glnx_tmpdir_delete (&fixture->tmpdir, NULL, NULL);
+}
+
+/* Test that the hash values for two #OstreeRepo instances pointing at the same
+ * repository are equal. We can’t test anything else, since hash collisions are
+ * always a possibility. */
+static void
+test_repo_hash (Fixture       *fixture,
+                gconstpointer  test_data)
+{
+  g_autoptr(GError) error = NULL;
+  g_autoptr(OstreeRepo) repo1 = ostree_repo_create_at (fixture->tmpdir.fd, ".",
+                                                       OSTREE_REPO_MODE_ARCHIVE_Z2,
+                                                       NULL,
+                                                       NULL, &error);
+  g_assert_no_error (error);
+
+  g_autoptr(OstreeRepo) repo2 = ostree_repo_open_at (fixture->tmpdir.fd, ".",
+                                                     NULL, &error);
+  g_assert_no_error (error);
+
+  g_assert_cmpuint (ostree_repo_hash (repo1), ==, ostree_repo_hash (repo2));
+}
+
+/* Test that trying to hash a closed repo results in an assertion failure. */
+static void
+test_repo_hash_closed (Fixture       *fixture,
+                       gconstpointer  test_data)
+{
+  if (g_test_subprocess ())
+    {
+      g_autoptr(GFile) repo_path = g_file_new_for_path (fixture->tmpdir.path);
+      g_autoptr(OstreeRepo) repo = ostree_repo_new (repo_path);
+
+      ostree_repo_hash (repo);
+
+      return;
+    }
+
+  g_test_trap_subprocess (NULL, 0, 0);
+  g_test_trap_assert_failed ();
+  g_test_trap_assert_stderr ("*ERROR*ostree_repo_hash: assertion failed:*");
+}
+
+/* Test that various repositories test equal (or not) with each other. */
+static void
+test_repo_equal (Fixture       *fixture,
+                 gconstpointer  test_data)
+{
+  g_autoptr(GError) error = NULL;
+
+  /* Create a few separate repos and some #OstreeRepo objects for them. */
+  glnx_ensure_dir (fixture->tmpdir.fd, "repo1", 0755, &error);
+  g_assert_no_error (error);
+  glnx_ensure_dir (fixture->tmpdir.fd, "repo2", 0755, &error);
+  g_assert_no_error (error);
+
+  g_autoptr(OstreeRepo) repo1 = ostree_repo_create_at (fixture->tmpdir.fd, "repo1",
+                                                       OSTREE_REPO_MODE_ARCHIVE_Z2,
+                                                       NULL,
+                                                       NULL, &error);
+  g_assert_no_error (error);
+
+  g_autoptr(OstreeRepo) repo1_alias = ostree_repo_open_at (fixture->tmpdir.fd, "repo1",
+                                                           NULL, &error);
+  g_assert_no_error (error);
+
+  g_autoptr(OstreeRepo) repo2 = ostree_repo_create_at (fixture->tmpdir.fd, "repo2",
+                                                       OSTREE_REPO_MODE_ARCHIVE_Z2,
+                                                       NULL,
+                                                       NULL, &error);
+  g_assert_no_error (error);
+
+  g_autoptr(GFile) closed_repo_path = g_file_new_for_path (fixture->tmpdir.path);
+  g_autoptr(OstreeRepo) closed_repo = ostree_repo_new (closed_repo_path);
+
+  /* Test various equalities. */
+  g_assert_true (ostree_repo_equal (repo1, repo1));
+  g_assert_true (ostree_repo_equal (repo1_alias, repo1_alias));
+  g_assert_true (ostree_repo_equal (repo1, repo1_alias));
+  g_assert_true (ostree_repo_equal (repo1_alias, repo1));
+  g_assert_true (ostree_repo_equal (repo2, repo2));
+  g_assert_false (ostree_repo_equal (repo1, repo2));
+  g_assert_false (ostree_repo_equal (repo1_alias, repo2));
+  g_assert_false (ostree_repo_equal (repo2, repo1));
+  g_assert_false (ostree_repo_equal (repo2, repo1_alias));
+  g_assert_false (ostree_repo_equal (repo1, closed_repo));
+  g_assert_false (ostree_repo_equal (repo1_alias, closed_repo));
+  g_assert_false (ostree_repo_equal (closed_repo, repo1));
+  g_assert_false (ostree_repo_equal (closed_repo, repo1_alias));
+  g_assert_false (ostree_repo_equal (repo2, closed_repo));
+  g_assert_false (ostree_repo_equal (closed_repo, repo2));
+  g_assert_false (ostree_repo_equal (closed_repo, closed_repo));
+}
+
+int
+main (int    argc,
+      char **argv)
+{
+  setlocale (LC_ALL, "");
+  g_test_init (&argc, &argv, NULL);
+
+  g_test_add ("/repo/hash", Fixture, NULL, setup,
+              test_repo_hash, teardown);
+  g_test_add ("/repo/hash/closed", Fixture, NULL, setup,
+              test_repo_hash_closed, teardown);
+  g_test_add ("/repo/equal", Fixture, NULL, setup,
+              test_repo_equal, teardown);
+
+  return g_test_run ();
+}