X-Git-Url: https://jasonwoof.com/gitweb/?p=wfpl.git;a=blobdiff_plain;f=mutex.php;fp=mutex.php;h=f6f4672b8d59ed43da6a962f14e68234217ef3e6;hp=0000000000000000000000000000000000000000;hb=646be7194f9fd096ef22f52074cf9c03d595b6ec;hpb=d7b26b0a9bfb6c894d15a5ff80b000df25188428

diff --git a/mutex.php b/mutex.php
new file mode 100644
index 0000000..f6f4672
--- /dev/null
+++ b/mutex.php
@@ -0,0 +1,33 @@
+<?php
+
+function mutex_lock ($name, $duration) {
+	while (true) {
+		$now = time();
+		$deleted_obsoletes = false;
+		db_insert('wfpl_mutexes', 'name,expires', $name, $now + $duration);
+		$id = db_auto_id();
+		$rows = db_get_assocs('wfpl_mutexes', 'id,name,expires', 'order by id');
+		$first_match = true;
+		foreach ($rows as $row) {
+			if ($row['expires'] < $now) {
+				if (!$deleted_obsoletes) {
+					db_delete('wfpl_mutexes', 'where expires < %i', $now);
+					$deleted_obsoletes = true;
+				}
+			} elseif ($row['name'] === $name) {
+				if ($row['id'] == $id) {
+					return $id;
+				} else {
+					break;
+				}
+			}
+		}
+		# not first
+		db_delete('wfpl_mutexes', 'where id=%i', $id);
+		sleep(1);
+	}
+}
+
+function mutex_unlock ($id) {
+	db_delete('wfpl_mutexes', 'where id=%i', $id);
+}