Skip to content

HTTPS clone URL

Subversion checkout URL

You can clone with
or
.
Download ZIP
Fetching contributors…

Cannot retrieve contributors at this time

144 lines (111 sloc) 3.536 kB
<?php
/**
* A Directed Acyclic Graph - used for doing topological sorts on dependencies, such as the before/after conditions
* in config yaml fragments
*/
class SS_DAG implements IteratorAggregate {
/**
* The nodes/vertices in the graph. Should be a numeric sequence of items (no string keys, no gaps).
* @var array|null
*/
protected $data;
/**
* The edges in the graph, in $to_idx => [$from_idx1, $from_idx2, ...] format
* @var array
*/
protected $dag;
public function __construct($data = null) {
$data = $data ? array_values($data) : array();
$this->data = $data;
$this->dag = array_fill_keys(array_keys($data), array());
}
/**
* Add another node/vertex
* @param $item anything - The item to add to the graph
*/
public function additem($item) {
$this->data[] = $item;
$this->dag[] = array();
}
/**
* Add an edge from one vertex to another.
*
* When passing actual nodes (as opposed to indexes), uses array_search with strict = true to find
*
* @param $from integer|any The index in $data of the node/vertex, or the node/vertex itself, that the edge
* goes from
* @param $to integer|any - The index in $data of the node/vertex, or the node/vertex itself, that the edge goes to
*/
public function addedge($from, $to) {
$i = is_numeric($from) ? $from : array_search($from, $this->data, true);
$j = is_numeric($to) ? $to : array_search($to, $this->data, true);
if ($i === false) throw new Exception("Couldnt find 'from' item in data when adding edge to DAG");
if ($j === false) throw new Exception("Couldnt find 'to' item in data when adding edge to DAG");
if (!isset($this->dag[$j])) $this->dag[$j] = array();
$this->dag[$j][] = $i;
}
/**
* Sort graph so that each node (a) comes before any nodes (b) where an edge exists from a to b
* @return array - The nodes
* @throws Exception - If the graph is cyclic (and so can't be sorted)
*/
public function sort() {
$data = $this->data; $dag = $this->dag; $sorted = array();
while (true) {
$withedges = array_filter($dag, 'count');
$starts = array_diff_key($dag, $withedges);
if (!count($starts)) break;
foreach ($starts as $i => $foo) $sorted[] = $data[$i];
foreach ($withedges as $j => $deps) {
$withedges[$j] = array_diff($withedges[$j], array_keys($starts));
}
$dag = $withedges;
}
if ($dag) {
$remainder = new SS_DAG($data); $remainder->dag = $dag;
throw new SS_DAG_CyclicException("DAG has cyclic requirements", $remainder);
}
return $sorted;
}
public function getIterator() {
return new SS_DAG_Iterator($this->data, $this->dag);
}
}
class SS_DAG_CyclicException extends Exception {
public $dag;
public function __construct($message, $dag) {
$this->dag = $dag;
parent::__construct($message);
}
}
class SS_DAG_Iterator implements Iterator {
protected $data;
protected $dag;
protected $dagkeys;
protected $i;
public function __construct($data, $dag) {
$this->data = $data;
$this->dag = $dag;
$this->rewind();
}
public function key() {
return $this->i;
}
public function current() {
$res = array();
$res['from'] = $this->data[$this->i];
$res['to'] = array();
foreach ($this->dag[$this->i] as $to) $res['to'][] = $this->data[$to];
return $res;
}
public function next() {
$this->i = array_shift($this->dagkeys);
}
public function rewind() {
$this->dagkeys = array_keys($this->dag);
$this->next();
}
public function valid() {
return $this->i !== null;
}
}
Jump to Line
Something went wrong with that request. Please try again.