[FileBackend] Simplified the shard list iterator to use AppendIterator and FilterIter...

Change-Id: I22f79447b1edec4fa6d7fc06d67f3f831a484f16

diff --git a/includes/filebackend/FileBackendStore.php b/includes/filebackend/FileBackendStore.php
index 5a91f9e..8b280e0 100644 (file)
--- a/includes/filebackend/FileBackendStore.php
+++ b/includes/filebackend/FileBackendStore.php
@@ -1798,21 +1798,15 @@ abstract class FileBackendStoreOpHandle {
  *
  * @ingroup FileBackend
  */
-abstract class FileBackendStoreShardListIterator implements Iterator {
+abstract class FileBackendStoreShardListIterator extends FilterIterator {
        /** @var FileBackendStore */
        protected $backend;
        /** @var Array */
        protected $params;
-       /** @var Array */
-       protected $shardSuffixes;
+
        protected $container; // string; full container name
        protected $directory; // string; resolved relative path
 
-       /** @var Traversable */
-       protected $iter;
-       protected $curShard = 0; // integer
-       protected $pos = 0; // integer
-
        /** @var Array */
        protected $multiShardPaths = array(); // (rel path => 1)
 
@@ -1829,142 +1823,56 @@ abstract class FileBackendStoreShardListIterator implements Iterator {
                $this->backend = $backend;
                $this->container = $container;
                $this->directory = $dir;
-               $this->shardSuffixes = $suffixes;
                $this->params = $params;
-       }
 
-       /**
-        * @see Iterator::key()
-        * @return integer
-        */
-       public function key() {
-               return $this->pos;
-       }
-
-       /**
-        * @see Iterator::valid()
-        * @return bool
-        */
-       public function valid() {
-               if ( $this->iter instanceof Iterator ) {
-                       return $this->iter->valid();
-               } elseif ( is_array( $this->iter ) ) {
-                       return ( current( $this->iter ) !== false ); // no paths can have this value
+               $iter = new AppendIterator();
+               foreach ( $suffixes as $suffix ) {
+                       $iter->append( $this->listFromShard( $this->container . $suffix ) );
                }
-               return false; // some failure?
-       }
-
-       /**
-        * @see Iterator::current()
-        * @return string|bool String or false
-        */
-       public function current() {
-               return ( $this->iter instanceof Iterator )
-                       ? $this->iter->current()
-                       : current( $this->iter );
-       }
-
-       /**
-        * @see Iterator::next()
-        * @return void
-        */
-       public function next() {
-               ++$this->pos;
-               ( $this->iter instanceof Iterator ) ? $this->iter->next() : next( $this->iter );
-               do {
-                       $continue = false; // keep scanning shards?
-                       $this->filterViaNext(); // filter out duplicates
-                       // Find the next non-empty shard if no elements are left
-                       if ( !$this->valid() ) {
-                               $this->nextShardIteratorIfNotValid();
-                               $continue = $this->valid(); // re-filter unless we ran out of shards
-                       }
-               } while ( $continue );
-       }
-
-       /**
-        * @see Iterator::rewind()
-        * @return void
-        */
-       public function rewind() {
-               $this->pos = 0;
-               $this->curShard = 0;
-               $this->setIteratorFromCurrentShard();
-               do {
-                       $continue = false; // keep scanning shards?
-                       $this->filterViaNext(); // filter out duplicates
-                       // Find the next non-empty shard if no elements are left
-                       if ( !$this->valid() ) {
-                               $this->nextShardIteratorIfNotValid();
-                               $continue = $this->valid(); // re-filter unless we ran out of shards
-                       }
-               } while ( $continue );
-       }
 
-       /**
-        * Filter out duplicate items by advancing to the next ones
-        */
-       protected function filterViaNext() {
-               while ( $this->valid() ) {
-                       $rel = $this->iter->current(); // path relative to given directory
-                       $path = $this->params['dir'] . "/{$rel}"; // full storage path
-                       if ( $this->backend->isSingleShardPathInternal( $path ) ) {
-                               break; // path is only on one shard; no issue with duplicates
-                       } elseif ( isset( $this->multiShardPaths[$rel] ) ) {
-                               // Don't keep listing paths that are on multiple shards
-                               ( $this->iter instanceof Iterator ) ? $this->iter->next() : next( $this->iter );
-                       } else {
-                               $this->multiShardPaths[$rel] = 1;
-                               break;
-                       }
-               }
+               parent::__construct( $iter );
        }
 
-       /**
-        * If the list iterator for this container shard is out of items,
-        * then move on to the next container that has items.
-        * If there are none, then it advances to the last container.
-        */
-       protected function nextShardIteratorIfNotValid() {
-               while ( !$this->valid() && ++$this->curShard < count( $this->shardSuffixes ) ) {
-                       $this->setIteratorFromCurrentShard();
+       public function accept() {
+               $rel = $this->getInnerIterator()->current(); // path relative to given directory
+               $path = $this->params['dir'] . "/{$rel}"; // full storage path
+               if ( $this->backend->isSingleShardPathInternal( $path ) ) {
+                       return true; // path is only on one shard; no issue with duplicates
+               } elseif ( isset( $this->multiShardPaths[$rel] ) ) {
+                       // Don't keep listing paths that are on multiple shards
+                       return false;
+               } else {
+                       $this->multiShardPaths[$rel] = 1;
+                       return true;
                }
        }
 
-       /**
-        * Set the list iterator to that of the current container shard
-        */
-       protected function setIteratorFromCurrentShard() {
-               $this->iter = $this->listFromShard(
-                       $this->container . $this->shardSuffixes[$this->curShard],
-                       $this->directory, $this->params );
-               // Start loading results so that current() works
-               if ( $this->iter ) {
-                       ( $this->iter instanceof Iterator ) ? $this->iter->rewind() : reset( $this->iter );
-               }
+       public function rewind() {
+               parent::rewind();
+               $this->multiShardPaths = array();
        }
 
        /**
         * Get the list for a given container shard
         *
         * @param string $container Resolved container name
-        * @param string $dir Resolved path relative to container
-        * @param array $params
-        * @return Traversable|Array|null
+        * @return Iterator
         */
-       abstract protected function listFromShard( $container, $dir, array $params );
+       abstract protected function listFromShard( $container );
 }
 
 /**
  * Iterator for listing directories
  */
 class FileBackendStoreShardDirIterator extends FileBackendStoreShardListIterator {
-       /**
-        * @see FileBackendStoreShardListIterator::listFromShard()
-        * @return Array|null|Traversable
-        */
-       protected function listFromShard( $container, $dir, array $params ) {
-               return $this->backend->getDirectoryListInternal( $container, $dir, $params );
+       protected function listFromShard( $container ) {
+               $list = $this->backend->getDirectoryListInternal(
+                       $container, $this->directory, $this->params );
+               if ( $list === null ) {
+                       return new ArrayIterator( array() );
+               } else {
+                       return is_array( $list ) ? new ArrayIterator( $list ) : $list;
+               }
        }
 }
 
@@ -1972,11 +1880,13 @@ class FileBackendStoreShardDirIterator extends FileBackendStoreShardListIterator
  * Iterator for listing regular files
  */
 class FileBackendStoreShardFileIterator extends FileBackendStoreShardListIterator {
-       /**
-        * @see FileBackendStoreShardListIterator::listFromShard()
-        * @return Array|null|Traversable
-        */
-       protected function listFromShard( $container, $dir, array $params ) {
-               return $this->backend->getFileListInternal( $container, $dir, $params );
+       protected function listFromShard( $container ) {
+               $list = $this->backend->getFileListInternal(
+                       $container, $this->directory, $this->params );
+               if ( $list === null ) {
+                       return new ArrayIterator( array() );
+               } else {
+                       return is_array( $list ) ? new ArrayIterator( $list ) : $list;
+               }
        }
 }