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<?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;
}}
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