Fix Feed Times on 32 Bit Servers

Summary:
The feed time is stored as the upper 32 bits of
PhabricatorFeedStoryData::chronologicalKey. These bits were previously accessed
by right shifting, which does not work properly on 32 bit machines (the result
is PHP_INT_MAX). We now attempt to use the bc extension (if available) and fall
back on mysql math otherwise. (See T500, D912).

Test Plan:
The calculation is unchanged for 64 bit machines. I checked both
paths on a 32 bit machine with bc extension available by setting the appropriate
if-condition to false and true.

Reviewers: epriestley

Reviewed By: epriestley

CC: ddfisher, aran, epriestley

Differential Revision: https://secure.phabricator.com/D1726

src/applications/feed/storage/story/PhabricatorFeedStoryData.php

@@ -1,7 +1,7 @@
 <?php
 
 /*
- * Copyright 2011 Facebook, Inc.
+ * Copyright 2012 Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -40,8 +40,28 @@ class PhabricatorFeedStoryData extends PhabricatorFeedDAO {
   }
 
   public function getEpoch() {
+    if (PHP_INT_SIZE < 8) {
+      // We're on a 32-bit machine.
+      if (function_exists('bcadd')) {
+        // Try to use the 'bc' extension.
+        return bcdiv($this->chronologicalKey, bcpow(2,32));
+      } else {
+        // Do the math in MySQL. TODO: If we formalize a bc dependency, get
+        // rid of this.
+        // See: PhabricatorFeedStoryPublisher::generateChronologicalKey()
+        $conn_r = id($this->establishConnection('r'));
+        $result = queryfx_one(
+          $conn_r,
+          // Insert the chronologicalKey as a string since longs don't seem to
+          // be supported by qsprintf and ints get maxed on 32 bit machines.
+          'SELECT (%s >> 32) as N',
+          $this->chronologicalKey);
+        return $result['N'];
+      }
+    } else {
       return $this->chronologicalKey >> 32;
     }
+  }
 
   public function getValue($key, $default = null) {
     return idx($this->storyData, $key, $default);

src/applications/feed/storage/story/__init__.php

@@ -9,6 +9,7 @@
 phutil_require_module('phabricator', 'applications/feed/storage/base');
 phutil_require_module('phabricator', 'applications/phid/constants');
 phutil_require_module('phabricator', 'applications/phid/storage/phid');
+phutil_require_module('phabricator', 'storage/queryfx');
 
 phutil_require_module('phutil', 'utils');