add XMLParser

stringXMLParser.php

@@ -0,0 +1,111 @@
+<?php
+
+error_reporting(E_ALL);
+
+/* Data can be send to coroutines using `$coroutine->send($data)`. The sent data will then
+ * be the result of the `yield` expression. Thus it can be received using a code like
+ * `$data = yield;`.
+ */
+
+/* What we're building in this script is a coroutine-based streaming XML parser. The PHP
+ * extension for parsing streamed XML is xml_parser. It is used by defining a set of
+ * callback functions for various events (like start tag, end tag, content).
+ *
+ * This event model makes the parsing process very complicated, because you basically
+ * have to implement your own state machine (which is a lot of boilerplate code the
+ * more complicated the XML gets).
+ *
+ * To solve this problem, we build a wrapper (the following function), which redirects
+ * the events to a coroutine ($target). This is done simply using
+ * `$target->send([$eventName, $data])`.
+ */
+function streamingXMLParser($target) {
+    $xmlParser = xml_parser_create();
+    xml_set_element_handler(
+        $xmlParser,
+        function ($xmlParser, $name, array $attributes) use ($target) {
+            $target->send(['start', [$name, $attributes]]);
+        },
+        function ($xmlParser, $name) use ($target) {
+            $target->send(['end', $name]);
+        }
+    );
+    xml_set_character_data_handler(
+        $xmlParser,
+        function ($xmlParser, $text) use ($target) {
+            $target->send(['text', $text]);
+        }
+    );
+
+    while ($data = yield) {
+        if (!xml_parse($xmlParser, $data)) {
+            throw new Exception(sprintf(
+                'XML error "%s" on line %d',
+                xml_error_string(xml_get_error_code($xmlParser)),
+                xml_get_current_line_number($xmlParser)
+            ));
+        }
+    }
+
+    xml_parser_free($xmlParser);
+}
+
+/* Inside the target coroutine the actual parsing happens. The events are received
+ * using `list($event, $data) = yield`. The main advantage that coroutines bring
+ * here is that you can fetch the events in nested loops. This way you are implicitly
+ * building a state machine (but the state is managed by PHP, not you!)
+ *
+ * This particular coroutine parses bus location data (for samples scroll down). The
+ * result is passed to another $target coroutine.
+ */
+function busXMLParser($target) {
+    while (true) {
+        list($event, $data) = yield;
+        if ($event == 'start' && $data[0] == 'BUS') {
+            $dict = [];
+            $content = '';
+            while (true) {
+                list($event, $data) = yield;
+                if ($event == 'start') {
+                    $content = '';
+                } elseif ($event == 'text') {
+                    $content .= $data;
+                } elseif ($event == 'end') {
+                    if ($data == 'BUS') {
+                        $target->send($dict);
+                        break;
+                    }
+
+                    $dict[strtolower($data)] = $content;
+                }
+            }
+        }
+    }
+}
+
+/* This coroutine prints out the info it receives from the bus XML parser. */
+function busLocationPrinter() {
+    while (true) {
+        $data = yield;
+        echo "Bus $data[id] is currently at $data[latitude]/$data[longitude]\n";
+    }
+}
+
+/* Here we are building up a coroutine pipeline. You should read this as:
+ * The streaming XML parser is passing data to the bus XML parser, which
+ * is passing data to the bus location printer.
+ */
+$parser = streamingXMLParser(busXMLParser(busLocationPrinter()));
+
+/* I don't have access to a real bus location API, so I'll just stream some
+ * fictional sample data */
+$parser->send('<?xml version="1.0"?><buses>');
+while (true) {
+    sleep(1);
+    $parser->send(sprintf(
+        '<bus><id>%d</id><latitude>%f</latitude><longitude>%f</longitude></bus>',
+        mt_rand(1, 1000), lcg_value(), lcg_value()
+    ));
+}
+
+/* If your head is buzzing now, that's a good thing :P */

t.php

@@ -24,6 +24,7 @@ function gen()
 {
     $i = 1;
     while (true) {
+        echo 'xx';
         yield $i += yield;
         echo $i, "\n";
     }
@@ -32,17 +33,38 @@ function gen()
 $gen = gen();
 var_dump($gen->send(3));
 $gen->next();
-echo "----\n";
-var_dump($gen->send(4));
-$gen->next();
-echo "----\n";
-$gen->send(5);
-$gen->next();
-echo "----\n";
-$gen->send(6);
-$gen->next();
-echo "----\n";
-$gen->send(7);
-$gen->next();
-echo "----\n";
+// echo "----\n";
+// var_dump($gen->send(4));
+// $gen->next();
+// echo "----\n";
+// $gen->send(5);
+// $gen->next();
+// echo "----\n";
+// $gen->send(6);
+// $gen->next();
+// echo "----\n";
+// $gen->send(7);
+// $gen->next();
+// echo "----\n";
+
+
+echo "\n\n";
+function agen()
+{
+    while (true) {
+        try {
+            var_dump (yield);
+        } catch (Exception $e) {
+            var_dump($e);
+        }
+    }
+}
+
+$ag = agen();
 
+$ag->send(1);
+$ag->send(2);
+$ag->throw(new Exception('a Exception'));
+$ag->send(3);
+$ag->send(4);
+$ag->send(5);