From 74b5fd193a940058f5c2c6d5e7d185a00a2e5038 Mon Sep 17 00:00:00 2001
From: Yuxuan Shui <yshuiv7@gmail.com>
Date: Fri, 16 Feb 2024 01:03:24 +0000
Subject: [PATCH] atom: add two-way mapping between atom and its name

Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>
---
 src/atom.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++----
 src/atom.h |  3 +++
 2 files changed, 49 insertions(+), 4 deletions(-)

diff --git a/src/atom.c b/src/atom.c
index fdcf73a9..5e17c0c3 100644
--- a/src/atom.c
+++ b/src/atom.c
@@ -1,4 +1,5 @@
 #include <string.h>
+#include <uthash.h>
 #include <xcb/xcb.h>
 
 #include "atom.h"
@@ -10,12 +11,14 @@
 
 struct atom_entry {
 	struct cache_handle entry;
+	UT_hash_handle hh;
 	xcb_atom_t atom;
 };
 
-static inline int atom_getter(struct cache *cache attr_unused, const char *atom_name,
+static inline int atom_getter(struct cache *cache, const char *atom_name,
                               struct cache_handle **value, void *user_data) {
 	xcb_connection_t *c = user_data;
+	auto atoms = container_of(cache, struct atom, c);
 	xcb_intern_atom_reply_t *reply = xcb_intern_atom_reply(
 	    c, xcb_intern_atom(c, 0, to_u16_checked(strlen(atom_name)), atom_name), NULL);
 
@@ -31,13 +34,25 @@ static inline int atom_getter(struct cache *cache attr_unused, const char *atom_
 
 	struct atom_entry *entry = ccalloc(1, struct atom_entry);
 	entry->atom = atom;
+	HASH_ADD_INT(atoms->atom_to_name, atom, entry);
 	*value = &entry->entry;
 	return 0;
 }
 
-static inline void
-atom_entry_free(struct cache *cache attr_unused, struct cache_handle *handle) {
-	struct atom_entry *entry = cache_entry(handle, struct atom_entry, entry);
+static inline int
+known_atom_getter(struct cache *cache attr_unused, const char *atom_name attr_unused,
+                  struct cache_handle **value, void *user_data) {
+	auto atom = *(xcb_atom_t *)user_data;
+	struct atom_entry *entry = ccalloc(1, struct atom_entry);
+	entry->atom = atom;
+	*value = &entry->entry;
+	return 0;
+}
+
+static inline void atom_entry_free(struct cache *cache, struct cache_handle *handle) {
+	auto entry = cache_entry(handle, struct atom_entry, entry);
+	auto atoms = container_of(cache, struct atom, c);
+	HASH_DEL(atoms->atom_to_name, entry);
 	free(entry);
 }
 
@@ -54,6 +69,33 @@ xcb_atom_t get_atom_cached(struct atom *a, const char *key) {
 	return cache_entry(cache_get(&a->c, key), struct atom_entry, entry)->atom;
 }
 
+const char *get_atom_name(struct atom *a, xcb_atom_t atom, xcb_connection_t *c) {
+	struct atom_entry *entry = NULL;
+	HASH_FIND(hh, a->atom_to_name, &atom, sizeof(xcb_atom_t), entry);
+	if (!entry) {
+		auto r = xcb_get_atom_name_reply(c, xcb_get_atom_name(c, atom), NULL);
+		if (!r) {
+			log_error("Failed to get atom name");
+			return NULL;
+		}
+		char *atom_name = xcb_get_atom_name_name(r);
+		struct cache_handle *handle = NULL;
+		cache_get_or_fetch(&a->c, atom_name, &handle, &atom, known_atom_getter);
+		entry = cache_entry(handle, struct atom_entry, entry);
+	}
+	HASH_ADD_INT(a->atom_to_name, atom, entry);
+	return entry->entry.key;
+}
+
+const char *get_atom_name_cached(struct atom *a, xcb_atom_t atom) {
+	struct atom_entry *entry = NULL;
+	HASH_FIND(hh, a->atom_to_name, &atom, sizeof(xcb_atom_t), entry);
+	if (!entry) {
+		return NULL;
+	}
+	return entry->entry.key;
+}
+
 /**
  * Create a new atom structure and fetch all predefined atoms
  */
diff --git a/src/atom.h b/src/atom.h
index 0cebe3a0..0b186095 100644
--- a/src/atom.h
+++ b/src/atom.h
@@ -54,6 +54,7 @@
 struct atom_entry;
 struct atom {
 	struct cache c;
+	struct atom_entry *atom_to_name;
 	LIST_APPLY(ATOM_DEF, SEP_COLON, ATOM_LIST1);
 	LIST_APPLY(ATOM_DEF, SEP_COLON, ATOM_LIST2);
 };
@@ -64,5 +65,7 @@ struct atom *init_atoms(xcb_connection_t *c);
 
 xcb_atom_t get_atom(struct atom *a, const char *key, xcb_connection_t *c);
 xcb_atom_t get_atom_cached(struct atom *a, const char *key);
+const char *get_atom_name(struct atom *a, xcb_atom_t, xcb_connection_t *c);
+const char *get_atom_name_cached(struct atom *a, xcb_atom_t atom);
 
 void destroy_atoms(struct atom *a);