From 38eb5ec7b286085b505b4cd088c2b9638eb5ae00 Mon Sep 17 00:00:00 2001
From: Louis Burda <quent.burda@gmail.com>
Date: Tue, 1 Mar 2022 15:02:40 +0100
Subject: Added lock for data directory

---
 src/data.c | 70 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 src/data.h |  4 ++++
 2 files changed, 74 insertions(+)

(limited to 'src')

diff --git a/src/data.c b/src/data.c
index 2ba102f..d8768b9 100644
--- a/src/data.c
+++ b/src/data.c
@@ -171,6 +171,12 @@ tracks_save(struct tag *tag)
 	free(index_path);
 }
 
+bool
+path_exists(const char *path)
+{
+	return access(path, F_OK) == 0;
+}
+
 bool
 make_dir(const char *path)
 {
@@ -493,6 +499,65 @@ track_rm(struct track *track, bool sync_fs)
 	return true;
 }
 
+bool
+aquire_lock(const char *datadir)
+{
+	char *lockpath, *procpath;
+	char linebuf[512];
+	FILE *file;
+	int pid;
+
+	lockpath = aprintf("%s/.lock", datadir);
+	OOM_CHECK(lockpath);
+
+	if (path_exists(lockpath)) {
+		file = fopen(lockpath, "r");
+		if (file == NULL) {
+			free(lockpath);
+			return false;
+		}
+
+		fread(linebuf, 1, sizeof(linebuf), file);
+		pid = atoi(linebuf);
+		procpath = aprintf("/proc/%i", pid);
+		OOM_CHECK(procpath);
+		if (path_exists(procpath)) {
+			free(procpath);
+			free(lockpath);
+			return false;
+		}
+		free(procpath);
+
+		fclose(file);
+	}
+
+	file = fopen(lockpath, "w+");
+	if (file == NULL) return false;
+	snprintf(linebuf, sizeof(linebuf), "%i", getpid());
+	fputs(linebuf, file);
+	fclose(file);
+
+	free(lockpath);
+
+	return true;
+}
+
+bool
+release_lock(const char *datadir)
+{
+	char *lockpath;
+	bool status;
+
+	lockpath = aprintf("%s/.lock", datadir);
+	OOM_CHECK(lockpath);
+
+	status = rm_file(lockpath);
+
+	free(lockpath);
+
+	return status;
+}
+
 void
 data_load(void)
 {
@@ -509,6 +574,9 @@ data_load(void)
 	datadir = getenv("TMUS_DATA");
 	if (!datadir) ERROR("TMUS_DATA not set!\n");
 
+	if (!aquire_lock(datadir))
+		ERROR("Failed to acquire lock\n");
+
 	dir = opendir(datadir);
 	if (!dir) ERROR("Failed to access dir: %s\n", datadir);
 
@@ -542,6 +610,8 @@ data_save(void)
 		tag = UPCAST(link, struct tag, link);
 		tracks_save(tag);
 	}
+
+	release_lock(datadir);
 }
 
 void
diff --git a/src/data.h b/src/data.h
index 63f2f64..7c5c92b 100644
--- a/src/data.h
+++ b/src/data.h
@@ -23,6 +23,7 @@ struct track {
 	struct link link_hs; /* player history */
 };
 
+bool path_exists(const char *path);
 bool make_dir(const char *path);
 bool rm_dir(const char *path, bool recursive);
 bool rm_file(const char *path);
@@ -45,6 +46,9 @@ bool tag_rm(struct tag *tag, bool sync_fs);
 struct track *track_add(struct tag *tag, const char *fname);
 bool track_rm(struct track *track, bool sync_fs);
 
+bool acquire_lock(const char *path);
+bool release_lock(const char *path);
+
 void data_load(void);
 void data_save(void);
 void data_free(void);
-- 
cgit v1.2.3-71-gd317