Currently `git_config()` uses a callback mechanism and file rereads for
config values. Due to this approach, it is not uncommon for the config
files to be parsed several times during the run of a git program, with
different callbacks picking out different variables useful to themselves.
Add a hash table to cache all key-value pairs read from config files
(repo specific .git/config, user wide ~/.gitconfig and the global
/etc/gitconfig). Add two external functions `git_config_get_string` and
`git_config_get_string_multi` for querying in a non-callback manner from the
hash table. They support O(1) lookups once the hash table is constructed.
Signed-off-by: Tanay Abhra <tanayabh@xxxxxxxxx>
---
Documentation/technical/api-config.txt | 26 ++++++
cache.h | 2 +
config.c | 144 +++++++++++++++++++++++++++++++++
3 files changed, 172 insertions(+)
diff --git a/Documentation/technical/api-config.txt b/Documentation/technical/api-config.txt
index 230b3a0..13f3f40 100644
--- a/Documentation/technical/api-config.txt
+++ b/Documentation/technical/api-config.txt
@@ -77,6 +77,32 @@ To read a specific file in git-config format, use
`git_config_from_file`. This takes the same callback and data parameters
as `git_config`.
+Querying For Specific Variables
+-------------------------------
+
+For programs wanting to query for specific variables in a non-callback
+manner, the config API provides two functions `git_config_get_string`
+and `git_config_get_string_multi`.They both read values from an internal
+cache generated previously from reading the config files.
+
+`git_config_get_string` takes two parameters,
+
+- a key string in canonical flat form for which the corresponding value
+ with the highest priority (i.e. value in the repo config will be
+ preferred over value in user wide config for the same variable) will
+ be retrieved.
+
+- a pointer to a string which will point to the retrieved value.
+
+`git_config_get_string` returns 0 for success, or -1 for no value found.
+
+`git_config_get_string_multi` returns a `string_list` containing all the
+values for the key passed as parameter, sorted in order of increasing
+priority (Note: NULL values are flagged as 1, check `util` for each
+'string_list_item` for flag value).
+
+See test-config.c for usage examples.
+
Value Parsing Helpers
---------------------
diff --git a/cache.h b/cache.h
index cbe1935..fec0a63 100644
--- a/cache.h
+++ b/cache.h
@@ -1294,6 +1294,8 @@ extern int check_repository_format_version(const char *var, const char *value, v
extern int git_env_bool(const char *, int);
extern int git_config_system(void);
extern int config_error_nonbool(const char *);
+extern int git_config_get_string(const char *, const char **);
+extern const struct string_list *git_config_get_string_multi(const char *);
#if defined(__GNUC__)
#define config_error_nonbool(s) (config_error_nonbool(s), const_error())
#endif
diff --git a/config.c b/config.c
index a1aef1c..6200f36 100644
--- a/config.c
+++ b/config.c
@@ -9,6 +9,8 @@
#include "exec_cmd.h"
#include "strbuf.h"
#include "quote.h"
+#include "hashmap.h"
+#include "string-list.h"
struct config_source {
struct config_source *prev;
@@ -37,6 +39,141 @@ static struct config_source *cf;
static int zlib_compression_seen;
+struct config_cache_entry {
+ struct hashmap_entry ent;
+ char *key;
+ struct string_list value_list;
+};
+
+static int hashmap_initialized;
+
+static int config_cache_add_value(const char *key, const char *value);
+
+static int config_cache_entry_cmp(const struct config_cache_entry *e1,
+ const struct config_cache_entry *e2, const void *unused)
+{
+ return strcmp(e1->key, e2->key);
+}
+
+static void config_cache_init(struct hashmap *config_cache)
+{
+ hashmap_init(config_cache, (hashmap_cmp_fn)config_cache_entry_cmp, 0);
+}
+
+static int config_cache_callback(const char *key, const char *value, void *unused)
+{
+ config_cache_add_value(key, value);
+ return 0;
+}
+
+static struct hashmap *get_config_cache(void)
+{
+ static struct hashmap config_cache;
+ if (!hashmap_initialized) {
+ config_cache_init(&config_cache);
+ hashmap_initialized = 1;
+ git_config(config_cache_callback, NULL);
+ }
+ return &config_cache;
+}
+
+static void config_cache_free(void)
+{
+ struct hashmap *config_cache;
+ struct config_cache_entry *entry;
+ struct hashmap_iter iter;
+ config_cache = get_config_cache();
+ hashmap_iter_init(config_cache, &iter);
+ while ((entry = hashmap_iter_next(&iter))) {
+ free(entry->key);
+ string_list_clear(&entry->value_list, 1);
+ }
+ hashmap_free(config_cache, 1);
+ hashmap_initialized = 0;
+}
+
+static struct config_cache_entry *config_cache_find_entry(const char *key)
+{
+ struct hashmap *config_cache;
+ struct config_cache_entry k;
+ struct config_cache_entry *found_entry;
+ char *normalized_key;
+ int ret;
+ config_cache = get_config_cache();
+ ret = git_config_parse_key(key, &normalized_key, NULL);
+
+ if (ret)
+ return NULL;
+
+ hashmap_entry_init(&k, strhash(normalized_key));
+ k.key = normalized_key;
+ found_entry = hashmap_get(config_cache, &k, NULL);
+ free(normalized_key);
+ return found_entry;
+}
+
+static struct string_list *config_cache_get_value(const char *key)
+{
+ struct config_cache_entry *e = config_cache_find_entry(key);
+ return e ? &e->value_list : NULL;
+}
+
+static int config_cache_add_value(const char *key, const char *value)
+{
+ struct hashmap *config_cache;
+ struct config_cache_entry *e;
+ struct string_list_item *item;
+ int *boolean_null_flag;
+
+ config_cache = get_config_cache();
+ e = config_cache_find_entry(key);
+
+ boolean_null_flag = xcalloc(1, sizeof(*boolean_null_flag));
+
+ if (!e) {
+ e = xmalloc(sizeof(*e));
+ hashmap_entry_init(e, strhash(key));
+ e->key = xstrdup(key);
+ string_list_init_dup(&e->value_list);
+ hashmap_add(config_cache, e);
+ }
+ /*
+ * If the variable had no value specified, the value will be NULL
+ * (typically this means it should be interpreted as boolean true).
+ * For such values, silently convert them to "BOOLEAN_NULL" to
+ * store in hashmap and flag that string_list_item as 1.
+ */
+ if (value == NULL) {
+ value = "BOOLEAN_NULL";
+ *boolean_null_flag = 1;
+ }
+ item = string_list_append(&e->value_list, value);
+ item->util = boolean_null_flag;
+
+ return 0;
+}
+
+int git_config_get_string(const char *key, const char **value)
+{
+ struct string_list *values;
+ int *flag;
+ values = config_cache_get_value(key);
+ if (!values)
+ return -1;
+ assert(values->nr > 0);
+ *value = values->items[values->nr - 1].string;
+ flag = values->items[values->nr - 1].util;
+ if (*flag)
+ *value = NULL;
+ return 0;
+}
+
+/* for NULL values, 'util' for each `string_list_item` is flagged as 1 */
+const struct string_list *git_config_get_string_multi(const char *key)
+{
+ return config_cache_get_value(key);
+}
+
static int config_file_fgetc(struct config_source *conf)
{
return fgetc(conf->u.file);
@@ -1708,6 +1845,13 @@ int git_config_set_multivar_in_file(const char *config_filename,
lock = NULL;
ret = 0;
+ /*
+ * content of config file has changed, so invalidate the
+ * config cache used by non-callback based query functions.
+ */
+ if (hashmap_initialized)
+ config_cache_free();
+
out_free:
if (lock)
rollback_lock_file(lock);
--
1.9.0.GIT
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