Replace SplStack with plain arrays

In PHP 7.x/8.x arrays outperform SplStack with noticable difference.

Author: NikoGrano

src/Context.php

@@ -5,7 +5,6 @@
 namespace JMS\Serializer;
 
 use JMS\Serializer\Exception\LogicException;
-use JMS\Serializer\Exception\RuntimeException;
 use JMS\Serializer\Exclusion\DepthExclusionStrategy;
 use JMS\Serializer\Exclusion\DisjunctExclusionStrategy;
 use JMS\Serializer\Exclusion\ExclusionStrategyInterface;
@@ -50,12 +49,11 @@ abstract class Context
      */
     private $initialized = false;
 
-    /** @var \SplStack */
-    private $metadataStack;
+    /** @var array<ClassMetadata|PropertyMetadata> */
+    private array $metadataStack = [];
 
     public function __construct()
     {
-        $this->metadataStack = new \SplStack();
     }
 
     public function initialize(string $format, VisitorInterface $visitor, GraphNavigatorInterface $navigator, MetadataFactoryInterface $factory): void
@@ -68,7 +66,7 @@ public function initialize(string $format, VisitorInterface $visitor, GraphNavig
         $this->visitor = $visitor;
         $this->navigator = $navigator;
         $this->metadataFactory = $factory;
-        $this->metadataStack = new \SplStack();
+        $this->metadataStack = [];
 
         if (isset($this->attributes['groups'])) {
             $this->addExclusionStrategy(new GroupsExclusionStrategy($this->attributes['groups']));
@@ -210,35 +208,50 @@ public function getFormat(): string
 
     public function pushClassMetadata(ClassMetadata $metadata): void
     {
-        $this->metadataStack->push($metadata);
+        $this->metadataStack[] = $metadata;
     }
 
     public function pushPropertyMetadata(PropertyMetadata $metadata): void
     {
-        $this->metadataStack->push($metadata);
+        $this->metadataStack[] = $metadata;
     }
 
     public function popPropertyMetadata(): void
     {
-        $metadata = $this->metadataStack->pop();
-
-        if (!$metadata instanceof PropertyMetadata) {
-            throw new RuntimeException('Context metadataStack not working well');
-        }
+        array_pop($this->metadataStack);
     }
 
     public function popClassMetadata(): void
     {
-        $metadata = $this->metadataStack->pop();
+        array_pop($this->metadataStack);
+    }
 
-        if (!$metadata instanceof ClassMetadata) {
-            throw new RuntimeException('Context metadataStack not working well');
-        }
+    /**
+     * Returns the metadata stack count without creating a copy.
+     */
+    public function getMetadataStackSize(): int
+    {
+        return \count($this->metadataStack);
+    }
+
+    /**
+     * Returns the top element of the metadata stack.
+     *
+     * @return ClassMetadata|PropertyMetadata
+     */
+    public function getMetadataStackTop()
+    {
+        return $this->metadataStack[\count($this->metadataStack) - 1];
     }
 
-    public function getMetadataStack(): \SplStack
+    /**
+     * Returns the metadata stack as an array with LIFO index order (0 = top/most recent).
+     *
+     * @return array<ClassMetadata|PropertyMetadata>
+     */
+    public function getMetadataStack(): array
     {
-        return $this->metadataStack;
+        return array_reverse($this->metadataStack);
     }
 
     public function getCurrentPath(): array
@@ -254,7 +267,7 @@ public function getCurrentPath(): array
             }
         }
 
-        return array_reverse($paths);
+        return $paths;
     }
 
     abstract public function getDepth(): int;

src/Exclusion/DepthExclusionStrategy.php

@@ -29,8 +29,7 @@ public function shouldSkipProperty(PropertyMetadata $property, Context $context)
 
     private function isTooDeep(Context $context): bool
     {
-        $stack = $context->getMetadataStack();
-        $currentCount = $stack->count();
+        $currentCount = $context->getMetadataStackSize();
 
         if ($currentCount === $this->cachedStackCount) {
             return $this->cachedResult;
@@ -42,6 +41,8 @@ private function isTooDeep(Context $context): bool
             return false;
         }
 
+        $stack = $context->getMetadataStack();
+
         if (!$this->hasMaxDepthOnStack && !$this->cachedResult && $currentCount > $this->cachedStackCount) {
             $delta = $currentCount - $this->cachedStackCount;
             $found = false;
@@ -68,7 +69,7 @@ private function isTooDeep(Context $context): bool
 
         // Full scan
         $relativeDepth = 0;
-        $top = $currentCount > 0 ? $stack->top() : null;
+        $top = $currentCount > 0 ? $stack[0] : null;
         $foundMaxDepth = false;
 
         foreach ($stack as $metadata) {

src/Handler/ArrayCollectionHandler.php

@@ -125,7 +125,7 @@ public function deserializeCollection(
             return $elements;
         }
 
-        $propertyMetadata = $context->getMetadataStack()->top();
+        $propertyMetadata = $context->getMetadataStackTop();
         if (!$propertyMetadata instanceof PropertyMetadata) {
             return $elements;
         }

src/SerializationContext.php

@@ -4,16 +4,15 @@
 
 namespace JMS\Serializer;
 
-use JMS\Serializer\Exception\RuntimeException;
 use Metadata\MetadataFactoryInterface;
 
 class SerializationContext extends Context
 {
     /** @var \SplObjectStorage */
     private $visitingSet;
 
-    /** @var \SplStack */
-    private $visitingStack;
+    /** @var object[] */
+    private array $visitingStack = [];
 
     /**
      * @var string
@@ -35,7 +34,7 @@ public function initialize(string $format, VisitorInterface $visitor, GraphNavig
         parent::initialize($format, $visitor, $navigator, $factory);
 
         $this->visitingSet = new \SplObjectStorage();
-        $this->visitingStack = new \SplStack();
+        $this->visitingStack = [];
     }
 
     /**
@@ -69,7 +68,7 @@ public function startVisiting($object): void
         }
 
         $this->visitingSet->offsetSet($object);
-        $this->visitingStack->push($object);
+        $this->visitingStack[] = $object;
     }
 
     /**
@@ -82,11 +81,7 @@ public function stopVisiting($object): void
         }
 
         $this->visitingSet->offsetUnset($object);
-        $poppedObject = $this->visitingStack->pop();
-
-        if ($object !== $poppedObject) {
-            throw new RuntimeException('Context visitingStack not working well');
-        }
+        array_pop($this->visitingStack);
     }
 
     /**
@@ -103,15 +98,15 @@ public function isVisiting($object): bool
 
     public function getPath(): ?string
     {
+        if (!$this->visitingStack) {
+            return null;
+        }
+
         $path = [];
         foreach ($this->visitingStack as $obj) {
             $path[] = \get_class($obj);
         }
 
-        if (!$path) {
-            return null;
-        }
-
         return implode(' -> ', $path);
     }
 
@@ -122,15 +117,20 @@ public function getDirection(): int
 
     public function getDepth(): int
     {
-        return $this->visitingStack->count();
+        return \count($this->visitingStack);
     }
 
     public function getObject(): ?object
     {
-        return !$this->visitingStack->isEmpty() ? $this->visitingStack->top() : null;
+        $n = \count($this->visitingStack);
+
+        return $n > 0 ? $this->visitingStack[$n - 1] : null;
     }
 
-    public function getVisitingStack(): \SplStack
+    /**
+     * @return object[]
+     */
+    public function getVisitingStack(): array
     {
         return $this->visitingStack;
     }