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<?php
namespace kch42\ste;
class Scope implements \ArrayAccess {
private $parent = NULL;
private $vars = array();
private static function parse_name($name) {
$remain = $name;
$fields = array();
while($remain !== "") {
$br_open = strpos($remain, '[');
if($br_open === false) {
$fields[] = $remain;
break;
}
$br_close = strpos($remain, ']', $br_open);
if($br_close === false) {
throw new RuntimeError("Invalid varname \"$name\". Missing closing \"]\".");
}
$fields[] = substr($remain, 0, $br_open);
$field = substr($remain, $br_open+1, $br_close-$br_open-1);
$more = substr($remain, $br_close+1);
if(strpos($field, '[') !== false) {
throw new RuntimeError("A variable field must not contain a '[' character.");
}
if((strlen($more) > 0) && ($more[0] !== '[')) {
// TODO: better error message, not very non-programmer friendly...
throw new RuntimeError("A variable name must be of format name('[' name ']')*.");
}
$remain = $field . $more;
}
return $fields;
}
private function &get_topvar_reference($name, $localonly) {
if(array_key_exists($name, $this->vars)) {
$ref = &$this->vars[$name];
return $ref;
}
if((!$localonly) && ($this->parent !== NULL)) {
$ref = &$this->parent->get_topvar_reference($name, $localonly);
return $ref;
}
throw new VarNotInScope();
}
public function &get_var_reference($name, $create_if_not_exist, $localonly=false) {
$nullref = NULL;
$fields = self::parse_name($name);
if(count($fields) == 0) {
return $nullref; // TODO: or should we throw an exception here?
}
$first = $fields[0];
$ref = NULL;
try {
$ref = &$this->get_topvar_reference($first, $localonly);
} catch(VarNotInScope $e) {
if($create_if_not_exist) {
$this->vars[$first] = (count($fields) > 0) ? array() : "";
$ref = &$this->vars[$first];
} else {
return $nullref;
}
}
for($i = 1; $i < count($fields); $i++) {
$field = $fields[$i];
if(!is_array($ref)) {
return $nullref;
}
if(!array_key_exists($field, $ref)) {
if(!$create_if_not_exist) {
return $nullref;
}
if($i < count($fields) - 1) {
$ref[$field] = array();
} else {
$ref[$field] = "";
}
}
$ref = &$ref[$field];
}
return $ref;
}
public function set_var_by_name($name, $val) {
$ref = &$this->get_var_reference($name, true);
$ref = $val;
}
public function set_local_var($name, $val) {
$ref = &$this->get_var_reference($name, true, true);
$ref = $val;
}
public function get_var_by_name($name) {
$ref = $this->get_var_reference($name, false);
return $ref === NULL ? "" : $ref;
}
public function new_subscope() {
$o = new self();
$o->parent = $this;
return $o;
}
/* implementing ArrayAccess */
public function offsetSet($offset, $value) {
$this->set_var_by_name($offset, $value);
}
public function offsetGet($offset) {
return $this->get_var_by_name($offset);
}
public function offsetExists($offset) {
try {
$this->get_topvar_reference($offset);
return true;
} catch(VarNotInScope $e) {
return false;
}
}
public function offsetUnset($offset) {
unset($this->vars[$offset]);
}
}
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