Cherry pick arenastring and PHP API

php/src/Google/Protobuf/FieldDescriptor.php

@@ -39,6 +39,7 @@ class FieldDescriptor
 {
     use GetPublicDescriptorTrait;
 
+    /** @var  \Google\Protobuf\Internal\FieldDescriptor $internal_desc */
     private $internal_desc;
 
     /**
@@ -81,6 +82,32 @@ public function getType()
         return $this->internal_desc->getType();
     }
 
+    /**
+     * @return OneofDescriptor
+     */
+    public function getContainingOneof()
+    {
+        return $this->getPublicDescriptor($this->internal_desc->getContainingOneof());
+    }
+
+    /**
+     * Gets the field's containing oneof, only if non-synthetic.
+     *
+     * @return null|OneofDescriptor
+     */
+    public function getRealContainingOneof()
+    {
+        return $this->getPublicDescriptor($this->internal_desc->getRealContainingOneof());
+    }
+
+    /**
+     * @return boolean
+     */
+    public function hasOptionalKeyword()
+    {
+        return $this->internal_desc->hasOptionalKeyword();
+    }
+
     /**
      * @return Descriptor Returns a descriptor for the field type if the field type is a message, otherwise throws \Exception
      * @throws \Exception
@@ -114,12 +141,4 @@ public function isMap()
     {
         return $this->internal_desc->isMap();
     }
-
-    /**
-     * @return boolean
-     */
-    public function hasOptionalKeyword()
-    {
-        return $this->internal_desc->hasOptionalKeyword();
-    }
 }

php/src/Google/Protobuf/Internal/FieldDescriptor.php

@@ -46,8 +46,11 @@ class FieldDescriptor
     private $message_type;
     private $enum_type;
     private $packed;
-    private $is_map;
     private $oneof_index = -1;
+    private $proto3_optional;
+
+    /** @var OneofDescriptor $containing_oneof */
+    private $containing_oneof;
 
     public function __construct()
     {
@@ -169,6 +172,32 @@ public function getPacked()
         return $this->packed;
     }
 
+    public function getProto3Optional()
+    {
+        return $this->proto3_optional;
+    }
+
+    public function setProto3Optional($proto3_optional)
+    {
+        $this->proto3_optional = $proto3_optional;
+    }
+
+    public function getContainingOneof()
+    {
+        return $this->containing_oneof;
+    }
+
+    public function setContainingOneof($containing_oneof)
+    {
+        $this->containing_oneof = $containing_oneof;
+    }
+
+    public function getRealContainingOneof()
+    {
+        return !is_null($this->containing_oneof) && !$this->containing_oneof->isSynthetic()
+            ? $this->containing_oneof : null;
+    }
+
     public function isPackable()
     {
         return $this->isRepeated() && self::isTypePackable($this->type);
@@ -214,6 +243,10 @@ private static function isTypePackable($field_type)
             $field_type !== GPBType::BYTES);
     }
 
+    /**
+     * @param FieldDescriptorProto $proto
+     * @return FieldDescriptor
+     */
     public static function getFieldDescriptor($proto)
     {
         $type_name = null;
@@ -248,8 +281,6 @@ public static function getFieldDescriptor($proto)
         $field = new FieldDescriptor();
         $field->setName($proto->getName());
 
-        $json_name = $proto->hasJsonName() ? $proto->getJsonName() :
-            lcfirst(implode('', array_map('ucwords', explode('_', $proto->getName()))));
         if ($proto->hasJsonName()) {
             $json_name = $proto->getJsonName();
         } else {
@@ -269,6 +300,7 @@ public static function getFieldDescriptor($proto)
         $field->setLabel($proto->getLabel());
         $field->setPacked($packed);
         $field->setOneofIndex($oneof_index);
+        $field->setProto3Optional($proto->getProto3Optional());
 
         // At this time, the message/enum type may have not been added to pool.
         // So we use the type name as place holder and will replace it with the

php/src/Google/Protobuf/Internal/OneofDescriptor.php

@@ -37,6 +37,7 @@ class OneofDescriptor
     use HasPublicDescriptorTrait;
 
     private $name;
+    /** @var \Google\Protobuf\FieldDescriptor[] $fields */
     private $fields;
 
     public function __construct()
@@ -64,13 +65,21 @@ public function getFields()
         return $this->fields;
     }
 
+    public function isSynthetic()
+    {
+        return !is_null($this->fields) && count($this->fields) === 1
+            && $this->fields[0]->getProto3Optional();
+    }
+
     public static function buildFromProto($oneof_proto, $desc, $index)
     {
         $oneof = new OneofDescriptor();
         $oneof->setName($oneof_proto->getName());
         foreach ($desc->getField() as $field) {
+            /** @var FieldDescriptor $field */
             if ($field->getOneofIndex() == $index) {
                 $oneof->addField($field);
+                $field->setContainingOneof($oneof);
             }
         }
         return $oneof;

php/src/Google/Protobuf/OneofDescriptor.php

@@ -38,6 +38,7 @@ class OneofDescriptor
 {
     use GetPublicDescriptorTrait;
 
+    /** @var  \Google\Protobuf\Internal\OneofDescriptor $internal_desc */
     private $internal_desc;
 
     /**
@@ -62,6 +63,12 @@ public function getName()
      */
     public function getField($index)
     {
+        if (
+            is_null($this->internal_desc->getFields())
+            || !isset($this->internal_desc->getFields()[$index])
+        ) {
+            return null;
+        }
         return $this->getPublicDescriptor($this->internal_desc->getFields()[$index]);
     }
 
@@ -75,6 +82,6 @@ public function getFieldCount()
 
     public function isSynthetic()
     {
-      return $this->internal_desc->isSynthetic();
+        return $this->internal_desc->isSynthetic();
     }
 }

src/google/protobuf/arena_impl.h

@@ -55,6 +55,13 @@ namespace google {
 namespace protobuf {
 namespace internal {
 
+// To prevent sharing cache lines between threads
+#ifdef __cpp_aligned_new
+enum { kCacheAlignment = 64 };
+#else
+enum { kCacheAlignment = alignof(max_align_t) };  // do the best we can
+#endif
+
 inline constexpr size_t AlignUpTo8(size_t n) {
   // Align n to next multiple of 8 (from Hacker's Delight, Chapter 3.)
   return (n + 7) & static_cast<size_t>(-8);
@@ -497,10 +504,10 @@ class PROTOBUF_EXPORT ThreadSafeArena {
   // have fallback function calls in tail position. This substantially improves
   // code for the happy path.
   PROTOBUF_NDEBUG_INLINE bool MaybeAllocateAligned(size_t n, void** out) {
-    SerialArena* a;
+    SerialArena* arena;
     if (PROTOBUF_PREDICT_TRUE(!alloc_policy_.should_record_allocs() &&
-                              GetSerialArenaFromThreadCache(&a))) {
-      return a->MaybeAllocateAligned(n, out);
+                              GetSerialArenaFromThreadCache(&arena))) {
+      return arena->MaybeAllocateAligned(n, out);
     }
     return false;
   }
@@ -564,7 +571,7 @@ class PROTOBUF_EXPORT ThreadSafeArena {
     // fast path optimizes the case where a single thread uses multiple arenas.
     ThreadCache* tc = &thread_cache();
     SerialArena* serial = hint_.load(std::memory_order_acquire);
-    if (PROTOBUF_PREDICT_TRUE(serial != NULL && serial->owner() == tc)) {
+    if (PROTOBUF_PREDICT_TRUE(serial != nullptr && serial->owner() == tc)) {
       *arena = serial;
       return true;
     }
@@ -602,15 +609,15 @@ class PROTOBUF_EXPORT ThreadSafeArena {
 #ifdef _MSC_VER
 #pragma warning(disable : 4324)
 #endif
-  struct alignas(64) ThreadCache {
+  struct alignas(kCacheAlignment) ThreadCache {
 #if defined(GOOGLE_PROTOBUF_NO_THREADLOCAL)
     // If we are using the ThreadLocalStorage class to store the ThreadCache,
     // then the ThreadCache's default constructor has to be responsible for
     // initializing it.
     ThreadCache()
         : next_lifecycle_id(0),
           last_lifecycle_id_seen(-1),
-          last_serial_arena(NULL) {}
+          last_serial_arena(nullptr) {}
 #endif
 
     // Number of per-thread lifecycle IDs to reserve. Must be power of two.
@@ -633,7 +640,7 @@ class PROTOBUF_EXPORT ThreadSafeArena {
 #ifdef _MSC_VER
 #pragma warning(disable : 4324)
 #endif
-  struct alignas(64) CacheAlignedLifecycleIdGenerator {
+  struct alignas(kCacheAlignment) CacheAlignedLifecycleIdGenerator {
     std::atomic<LifecycleIdAtomic> id;
   };
   static CacheAlignedLifecycleIdGenerator lifecycle_id_generator_;

src/google/protobuf/arenastring.cc

@@ -187,7 +187,7 @@ std::string* ArenaStringPtr::Release() {
   if (IsDefault()) return nullptr;
 
   std::string* released = tagged_ptr_.Get();
-  if (!tagged_ptr_.IsAllocated()) {
+  if (tagged_ptr_.IsArena()) {
     released = tagged_ptr_.IsMutable() ? new std::string(std::move(*released))
                                        : new std::string(*released);
   }
@@ -216,9 +216,7 @@ void ArenaStringPtr::SetAllocated(std::string* value, Arena* arena) {
 }
 
 void ArenaStringPtr::Destroy() {
-  if (tagged_ptr_.IsAllocated()) {
-    delete tagged_ptr_.Get();
-  }
+  delete tagged_ptr_.GetIfAllocated();
 }
 
 void ArenaStringPtr::ClearToEmpty() {

src/google/protobuf/arenastring.h

@@ -96,13 +96,12 @@ class PROTOBUF_EXPORT LazyString {
 
 class TaggedStringPtr {
  public:
-  // Bit flags qualifying string properties. We can use up to 3 bits as
-  // ptr_ is guaranteed and enforced to be aligned on 8 byte boundaries.
+  // Bit flags qualifying string properties. We can use 2 bits as
+  // ptr_ is guaranteed and enforced to be aligned on 4 byte boundaries.
   enum Flags {
     kArenaBit = 0x1,      // ptr is arena allocated
-    kAllocatedBit = 0x2,  // ptr is heap allocated
-    kMutableBit = 0x4,    // ptr contents are fully mutable
-    kMask = 0x7           // Bit mask
+    kMutableBit = 0x2,    // ptr contents are fully mutable
+    kMask = 0x3           // Bit mask
   };
 
   // Composed logical types
@@ -112,7 +111,7 @@ class TaggedStringPtr {
 
     // Allocated strings are mutable and (as the name implies) owned.
     // A heap allocated string must be deleted.
-    kAllocated = kAllocatedBit | kMutableBit,
+    kAllocated = kMutableBit,
 
     // Mutable arena strings are strings where the string instance is owned
     // by the arena, but the string contents itself are owned by the string
@@ -166,8 +165,16 @@ class TaggedStringPtr {
   // Returns true if the current string is an immutable default value.
   inline bool IsDefault() const { return (as_int() & kMask) == kDefault; }
 
-  // Returns true if the current string is a heap allocated mutable value.
-  inline bool IsAllocated() const { return as_int() & kAllocatedBit; }
+  // If the current string is a heap-allocated mutable value, returns a pointer
+  // to it.  Returns nullptr otherwise.
+  inline std::string *GetIfAllocated() const {
+    auto allocated = as_int() ^ kAllocated;
+    if (allocated & kMask) return nullptr;
+
+    auto ptr = reinterpret_cast<std::string*>(allocated);
+    PROTOBUF_ASSUME(ptr != nullptr);
+    return ptr;
+  }
 
   // Returns true if the current string is an arena allocated value.
   // This means it's either a mutable or fixed size arena string.
@@ -224,8 +231,8 @@ static_assert(std::is_trivial<TaggedStringPtr>::value,
 // Because ArenaStringPtr is used in oneof unions, its constructor is a NOP and
 // the field is always manually initialized via method calls.
 //
-// See TaggedPtr for more information about the types of string values being
-// held, and the mutable and ownership invariants for each type.
+// See TaggedStringPtr for more information about the types of string values
+// being held, and the mutable and ownership invariants for each type.
 struct PROTOBUF_EXPORT ArenaStringPtr {
   ArenaStringPtr() = default;
   constexpr ArenaStringPtr(ExplicitlyConstructedArenaString* default_value,