Streaming JSON serializer.
Usage:
try {
$s = new JsonStream(STDOUT);
$s->startObject();
$s->writeProperty('name', 'John');
$s->writeProperty('age', 32);
$s->writeKey('pets')
->startArray()
->write('Garfield')
->write('Ido')
->end();
$s->writeProperty('data', array('list' => array(), 'of' => 'precompiled stuff'));
$s->close();
}
catch (JsonStreamException $e) {
error_log(var_export($e->getJsonState(), TRUE));
throw $e;
}
| <?php | |
| define('JSON_STREAM_ERROR_OOO', 1); | |
| class JsonStreamException extends Exception { | |
| private $json_state; | |
| public function __construct($message = "", $code = 0, $state = NULL, $previous = NULL) { | |
| parent::__construct($message, $code, $previous); | |
| $this->json_state = $state; | |
| } | |
| public function getJsonState() { | |
| return $this->json_state; | |
| } | |
| } | |
| class JsonStream { | |
| private $fd; | |
| private $state; | |
| public function __construct($fd) { | |
| $this->fd = $fd; | |
| $this->state = array(); | |
| } | |
| private function currentState() { | |
| return current(array_slice($this->state, -1)); | |
| } | |
| private function pushState($state) { | |
| array_push($this->state, $state); | |
| } | |
| private function popState() { | |
| return array_pop($this->state); | |
| } | |
| private function acceptsValue() { | |
| $state = $this->currentState(); | |
| return | |
| !$state || | |
| $state->type == 'array' || | |
| ($state->type == 'object' && $state->at_key); | |
| } | |
| public function startArray() { | |
| $this->writeLiteral('['); | |
| $this->pushState((object)array( | |
| 'type' => 'array', | |
| 'has_items' => FALSE | |
| )); | |
| return $this; | |
| } | |
| public function startObject() { | |
| $this->writeLiteral('{'); | |
| $this->pushState((object)array( | |
| 'type' => 'object', | |
| 'at_key' => FALSE, | |
| 'has_items' => FALSE, | |
| )); | |
| return $this; | |
| } | |
| public function end() { | |
| $state = $this->popState(); | |
| if (!$state || ($state->type == 'object' && $state->at_key)) { | |
| throw new JsonStreamException("Operation out of order.", JSON_STREAM_ERROR_OOO, $state); | |
| } | |
| if ($state->type == 'object') { | |
| fwrite($this->fd, '}'); | |
| } | |
| else if ($state->type == 'array') { | |
| fwrite($this->fd, ']'); | |
| } | |
| } | |
| public function writeProperty($key, $value) { | |
| $this->writeKey($key); | |
| $this->write($value); | |
| return $this; | |
| } | |
| public function writeKey($key) { | |
| $state = $this->currentState(); | |
| if ($state->type != 'object' || $state->at_key) { | |
| throw new JsonStreamException("Operation out of order.", JSON_STREAM_ERROR_OOO, $state); | |
| } | |
| if ($state->has_items) { | |
| fwrite($this->fd, ','); | |
| } | |
| $state->has_items = TRUE; | |
| $state->at_key = TRUE; | |
| fwrite($this->fd, json_encode($key)); | |
| fwrite($this->fd, ':'); | |
| return $this; | |
| } | |
| public function writeLiteral($literal) { | |
| $state = $this->currentState(); | |
| if (!$this->acceptsValue()) { | |
| throw new JsonStreamException("Operation out of order.", JSON_STREAM_ERROR_OOO, $state); | |
| } | |
| if ($state) { | |
| if ($state->type == 'object') { | |
| $state->at_key = FALSE; | |
| } | |
| else if ($state->type == 'array') { | |
| if ($state->has_items) { | |
| fwrite($this->fd, ','); | |
| } | |
| $state->has_items = TRUE; | |
| } | |
| } | |
| fwrite($this->fd, $literal); | |
| return $this; | |
| } | |
| public function write($value) { | |
| $this->writeLiteral(json_encode($value)); | |
| return $this; | |
| } | |
| public function close($newline = FALSE) { | |
| while ($this->currentState()) { | |
| $this->end(); | |
| } | |
| if ($newline) { | |
| fwrite($this->fd, "\n"); | |
| } | |
| fclose($this->fd); | |
| } | |
| } |