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-rw-r--r--include/lock.php76
1 files changed, 76 insertions, 0 deletions
diff --git a/include/lock.php b/include/lock.php
new file mode 100644
index 000000000..be6130e1d
--- /dev/null
+++ b/include/lock.php
@@ -0,0 +1,76 @@
+<?php
+
+// Provide some ability to lock a PHP function so that multiple processes
+// can't run the function concurrently
+// The function must have a line inserted into the 'lock' table with the
+// function's name in the 'name' field
+if(! function_exists('lock_function')) {
+function lock_function($fn_name, $block = true, $wait_sec = 2) {
+ if( $wait_sec == 0 )
+ $wait_sec = 2; // don't let the user pick a value that's likely to crash the system
+
+ $got_lock = false;
+
+ do {
+ q("LOCK TABLE lock WRITE");
+ $r = q("SELECT locked FROM lock WHERE name = '%s' LIMIT 1",
+ dbesc($fn_name)
+ );
+
+ if((count($r)) && (! $r[0]['locked'])) {
+ q("UPDATE lock SET locked = 1 WHERE name = '%s' LIMIT 1",
+ dbesc($fn_name)
+ );
+ $got_lock = true;
+ }
+ elseif(! $r) { // the Boolean value for count($r) should be equivalent to the Boolean value of $r
+ q("INSERT INTO lock ( name, locked ) VALUES ( '%s', 1 )",
+ dbesc($fn_name)
+ );
+ $got_lock = true;
+ }
+
+ q("UNLOCK TABLES");
+
+ if(($block) && (! $got_lock))
+ sleep($wait_sec);
+
+ } while(($block) && (! $got_lock));
+
+ logger('lock_function: function ' . $fn_name . ' with blocking = ' . $block . ' got_lock = ' . $got_lock, LOGGER_DEBUG);
+
+ return $got_lock;
+}}
+
+
+if(! function_exists('block_on_function_lock')) {
+function block_on_function_lock($fn_name, $wait_sec = 2) {
+ if( $wait_sec == 0 )
+ $wait_sec = 2; // don't let the user pick a value that's likely to crash the system
+
+ do {
+ $r = q("SELECT locked FROM lock WHERE name = '%s' LIMIT 1",
+ dbesc(fn_name)
+ );
+
+ if(count($r) && $r[0]['locked'])
+ sleep($wait_sec);
+
+ } while(count($r) && $r[0]['locked']);
+
+ return;
+}}
+
+
+if(! function_exists('unlock_function')) {
+function unlock_function(fn_name) {
+ //$r = q("LOCK TABLE lock WRITE");
+ $r = q("UPDATE lock SET locked = 0 WHERE name = '%s' LIMIT 1",
+ dbesc(fn_name)
+ );
+ //$r = q("UNLOCK TABLES");
+
+ logger('unlock_function: released lock for function ' . fn_name, LOGGER_DEBUG);
+
+ return;
+}}