function has_capability_in_accessdata($capability, $context, $accessdata, $doanything) {
global $CFG;

/// build $paths as a list of current + all parent "paths" with order bottom-to-top
$contextids = explode('/', $context->path);
$paths = array($context->path);
while (count($contextids) > 2) { array_pop($contextids); $paths[] = implode('/', $contextids); }

$roles = array();
$switchedrole = false;

/// Find out if role switched
if (isset($accessdata['rsw'])) {
// check for isset() is fast
// empty() is slow...
if (empty($accessdata['rsw'])) { unset($accessdata['rsw']); // keep things fast and unambiguous break; }

// From the bottom up...

foreach ($paths as $path) {
if (isset($accessdata['rsw'][$ctxp])) { // Found a switchrole assignment // check for that role _plus_ the default user role $roles = array($accessdata['rsw'][$ctxp]=>null, $CFG->defaultuserroleid=>null); $switchedrole = true; break; }
}
}

if (!$switchedrole) {
// get all users roles in this context and above
foreach ($paths as $path) {
if (isset($accessdata['ra'][$path])) {
foreach ($accessdata['ra'][$path] as $roleid) { $roles[$roleid] = null; }
}
}

// Find out if user is admin - do anything is allowed in system context only since 2.0
// do anything is ignored when switching roles - it is not allowed to switch to admin role anyway
if ($doanything) {
$systempath = '/'.SYSCONTEXTID;
foreach ($roles as $roleid=>$ignored) {
if (isset($accessdata['rdef']["{$systempath}:$roleid"]['moodle/site:doanything'])
and $accessdata['rdef']["{$systempath}:$roleid"]['moodle/site:doanything'] == CAP_ALLOW) { return true; }
}
}
}

/// Now find out what access is given to each role
/// going from bottom-->up - the lowes override wins unless there is a CAP_PROHIBIT somewhere above tested context
foreach ($roles as $roleid=>$ignored) {
$access = null;
foreach ($paths as $path) {
if (isset($accessdata['rdef']["{$path}:$roleid"][$capability])) {
$perm = (int)$accessdata['rdef']["{$path}:$roleid"][$capability];
if ($perm === CAP_PROHIBIT or is_null($roles[$roleid])) { $roles[$roleid] = $perm; }
}
}
}

// any CAP_PROHIBIT found means no access
if (array_search(CAP_PROHIBIT, $roles) !== false) { return false; }

// at least one CAP_ALLOW means user has access
return (array_search(CAP_ALLOW, $roles) !== false);
}