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authorCarlos Martín Nieto <cmn@dwim.me>2015-06-01 20:02:23 +0200
committerCarlos Martín Nieto <cmn@dwim.me>2015-08-12 04:09:38 +0200
commit36f784b538c4b27f7b52427d2cfce06c535abba0 (patch)
treecea0d9dd8e9807e30583ba54c5aa2e58c6c14fe2
parentb1667039640ba3464ea0e2d13ad28c9244d80b4d (diff)
downloadlibgit2-36f784b538c4b27f7b52427d2cfce06c535abba0.tar.gz
config: expose locking via the main API
This lock/unlock pair allows for the cller to lock a configuration file to avoid concurrent operations. It also allows for a transactional approach to updating a configuration file. If multiple updates must be made atomically, they can be done while the config is locked.
-rw-r--r--CHANGELOG.md10
-rw-r--r--include/git2/config.h27
-rw-r--r--src/config.c31
-rw-r--r--tests/config/write.c41
4 files changed, 90 insertions, 19 deletions
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 243b696d7..4442d0a3f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,12 @@ v0.23 + 1
### API additions
+* `git_config_lock()` and `git_config_unlock()` have been added, which
+ allow for transactional/atomic complex updates to the configuration,
+ removing the opportunity for concurrent operations and not
+ committing any changes until the unlock.
+
+
### API removals
### Breaking API changes
@@ -19,6 +25,10 @@ v0.23 + 1
with the reflog on ref deletion. The file-based backend must delete
it, a database-backed one may wish to archive it.
+* `git_config_backend` has gained two entries. `lock` and `unlock`
+ with which to implement the transactional/atomic semantics for the
+ configuration backend.
+
v0.23
------
diff --git a/include/git2/config.h b/include/git2/config.h
index 6d3fdb0c2..2550f8edb 100644
--- a/include/git2/config.h
+++ b/include/git2/config.h
@@ -689,6 +689,33 @@ GIT_EXTERN(int) git_config_backend_foreach_match(
void *payload);
+/**
+ * Lock the backend with the highest priority
+ *
+ * Locking disallows anybody else from writing to that backend. Any
+ * updates made after locking will not be visible to a reader until
+ * the file is unlocked.
+ *
+ * @param cfg the configuration in which to lock
+ * @return 0 or an error code
+ */
+GIT_EXTERN(int) git_config_lock(git_config *cfg);
+
+/**
+ * Unlock the backend with the highest priority
+ *
+ * Unlocking will allow other writers to updat the configuration
+ * file. Optionally, any changes performed since the lock will be
+ * applied to the configuration.
+ *
+ * @param cfg the configuration
+ * @param commit boolean which indicates whether to commit any changes
+ * done since locking
+ * @return 0 or an error code
+ */
+GIT_EXTERN(int) git_config_unlock(git_config *cfg, int commit);
+
+
/** @} */
GIT_END_DECL
#endif
diff --git a/src/config.c b/src/config.c
index 77cf573e6..937d00dcb 100644
--- a/src/config.c
+++ b/src/config.c
@@ -1144,6 +1144,37 @@ int git_config_open_default(git_config **out)
return error;
}
+int git_config_lock(git_config *cfg)
+{
+ git_config_backend *file;
+ file_internal *internal;
+
+ internal = git_vector_get(&cfg->files, 0);
+ if (!internal || !internal->file) {
+ giterr_set(GITERR_CONFIG, "cannot lock; the config has no backends/files");
+ return -1;
+ }
+ file = internal->file;
+
+ return file->lock(file);
+}
+
+int git_config_unlock(git_config *cfg, int commit)
+{
+ git_config_backend *file;
+ file_internal *internal;
+
+ internal = git_vector_get(&cfg->files, 0);
+ if (!internal || !internal->file) {
+ giterr_set(GITERR_CONFIG, "cannot lock; the config has no backends/files");
+ return -1;
+ }
+
+ file = internal->file;
+
+ return file->unlock(file, commit);
+}
+
/***********
* Parsers
***********/
diff --git a/tests/config/write.c b/tests/config/write.c
index 5446b95c3..e43c26bd9 100644
--- a/tests/config/write.c
+++ b/tests/config/write.c
@@ -635,44 +635,47 @@ void test_config_write__to_file_with_only_comment(void)
void test_config_write__locking(void)
{
- git_config_backend *cfg, *cfg2;
+ git_config *cfg, *cfg2;
git_config_entry *entry;
const char *filename = "locked-file";
/* Open the config and lock it */
cl_git_mkfile(filename, "[section]\n\tname = value\n");
- cl_git_pass(git_config_file__ondisk(&cfg, filename));
- cl_git_pass(git_config_file_open(cfg, GIT_CONFIG_LEVEL_APP));
- cl_git_pass(git_config_file_get_string(&entry, cfg, "section.name"));
+ cl_git_pass(git_config_open_ondisk(&cfg, filename));
+ cl_git_pass(git_config_get_entry(&entry, cfg, "section.name"));
cl_assert_equal_s("value", entry->value);
git_config_entry_free(entry);
- cl_git_pass(git_config_file_lock(cfg));
+ cl_git_pass(git_config_lock(cfg));
/* Change entries in the locked backend */
- cl_git_pass(git_config_file_set_string(cfg, "section.name", "other value"));
- cl_git_pass(git_config_file_set_string(cfg, "section2.name3", "more value"));
+ cl_git_pass(git_config_set_string(cfg, "section.name", "other value"));
+ cl_git_pass(git_config_set_string(cfg, "section2.name3", "more value"));
/* We can see that the file we read from hasn't changed */
- cl_git_pass(git_config_file__ondisk(&cfg2, filename));
- cl_git_pass(git_config_file_open(cfg2, GIT_CONFIG_LEVEL_APP));
- cl_git_pass(git_config_file_get_string(&entry, cfg2, "section.name"));
+ cl_git_pass(git_config_open_ondisk(&cfg2, filename));
+ cl_git_pass(git_config_get_entry(&entry, cfg2, "section.name"));
cl_assert_equal_s("value", entry->value);
git_config_entry_free(entry);
- cl_git_fail_with(GIT_ENOTFOUND, git_config_file_get_string(&entry, cfg2, "section2.name3"));
- git_config_file_free(cfg2);
+ cl_git_fail_with(GIT_ENOTFOUND, git_config_get_entry(&entry, cfg2, "section2.name3"));
+ git_config_free(cfg2);
- git_config_file_unlock(cfg, true);
- git_config_file_free(cfg);
+ /* And we also get the old view when we read from the locked config */
+ cl_git_pass(git_config_get_entry(&entry, cfg, "section.name"));
+ cl_assert_equal_s("value", entry->value);
+ git_config_entry_free(entry);
+ cl_git_fail_with(GIT_ENOTFOUND, git_config_get_entry(&entry, cfg, "section2.name3"));
+
+ git_config_unlock(cfg, true);
+ git_config_free(cfg);
/* Now that we've unlocked it, we should see both updates */
- cl_git_pass(git_config_file__ondisk(&cfg, filename));
- cl_git_pass(git_config_file_open(cfg, GIT_CONFIG_LEVEL_APP));
- cl_git_pass(git_config_file_get_string(&entry, cfg, "section.name"));
+ cl_git_pass(git_config_open_ondisk(&cfg, filename));
+ cl_git_pass(git_config_get_entry(&entry, cfg, "section.name"));
cl_assert_equal_s("other value", entry->value);
git_config_entry_free(entry);
- cl_git_pass(git_config_file_get_string(&entry, cfg, "section2.name3"));
+ cl_git_pass(git_config_get_entry(&entry, cfg, "section2.name3"));
cl_assert_equal_s("more value", entry->value);
git_config_entry_free(entry);
- git_config_file_free(cfg);
+ git_config_free(cfg);
}