Merge "Fix SharedBuffer. Remove aref."

include/cutils/aref.h

@@ -1,58 +0,0 @@
-/*
- * Copyright (C) 2013 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-#ifndef _CUTILS_AREF_H_
-#define _CUTILS_AREF_H_
-
-#include <stddef.h>
-#include <sys/cdefs.h>
-
-#include <cutils/atomic.h>
-
-__BEGIN_DECLS
-
-#define AREF_TO_ITEM(aref, container, member) \
-    (container *) (((char*) (aref)) - offsetof(container, member))
-
-struct aref
-{
-    volatile int32_t count;
-};
-
-static inline void aref_init(struct aref *r)
-{
-    r->count = 1;
-}
-
-static inline int32_t aref_count(struct aref *r)
-{
-    return r->count;
-}
-
-static inline void aref_get(struct aref *r)
-{
-    android_atomic_inc(&r->count);
-}
-
-static inline void aref_put(struct aref *r, void (*release)(struct aref *))
-{
-    if (android_atomic_dec(&r->count) == 1)
-        release(r);
-}
-
-__END_DECLS
-
-#endif // _CUTILS_AREF_H_

libutils/SharedBuffer.cpp

@@ -20,7 +20,6 @@
 #include <string.h>
 
 #include <log/log.h>
-#include <utils/Atomic.h>
 
 #include "SharedBuffer.h"
 
@@ -37,18 +36,19 @@ SharedBuffer* SharedBuffer::alloc(size_t size)
 
     SharedBuffer* sb = static_cast<SharedBuffer *>(malloc(sizeof(SharedBuffer) + size));
     if (sb) {
-        sb->mRefs = 1;
+        // Should be std::atomic_init(&sb->mRefs, 1);
+        // But that generates a warning with some compilers.
+        // The following is OK on Android-supported platforms.
+        sb->mRefs.store(1, std::memory_order_relaxed);
         sb->mSize = size;
     }
     return sb;
 }
 
 
-ssize_t SharedBuffer::dealloc(const SharedBuffer* released)
+void SharedBuffer::dealloc(const SharedBuffer* released)
 {
-    if (released->mRefs != 0) return -1; // XXX: invalid operation
     free(const_cast<SharedBuffer*>(released));
-    return 0;
 }
 
 SharedBuffer* SharedBuffer::edit() const
@@ -108,14 +108,15 @@ SharedBuffer* SharedBuffer::reset(size_t new_size) const
 }
 
 void SharedBuffer::acquire() const {
-    android_atomic_inc(&mRefs);
+    mRefs.fetch_add(1, std::memory_order_relaxed);
 }
 
 int32_t SharedBuffer::release(uint32_t flags) const
 {
     int32_t prev = 1;
-    if (onlyOwner() || ((prev = android_atomic_dec(&mRefs)) == 1)) {
+    if (onlyOwner() || ((prev = mRefs.fetch_sub(1, std::memory_order_release) == 1)
-        mRefs = 0;
+            && (atomic_thread_fence(std::memory_order_acquire), true))) {
+        mRefs.store(0, std::memory_order_relaxed);
         if ((flags & eKeepStorage) == 0) {
             free(const_cast<SharedBuffer*>(this));
         }

libutils/SharedBuffer.h

@@ -14,9 +14,14 @@
  * limitations under the License.
  */
 
+/*
+ * DEPRECATED.  DO NOT USE FOR NEW CODE.
+ */
+
 #ifndef ANDROID_SHARED_BUFFER_H
 #define ANDROID_SHARED_BUFFER_H
 
+#include <atomic>
 #include <stdint.h>
 #include <sys/types.h>
 
@@ -43,7 +48,7 @@ public:
      * In other words, the buffer must have been release by all its
      * users.
      */
-    static          ssize_t                 dealloc(const SharedBuffer* released);
+    static          void                    dealloc(const SharedBuffer* released);
 
     //! access the data for read
     inline          const void*             data() const;
@@ -94,12 +99,16 @@ private:
         SharedBuffer(const SharedBuffer&);
         SharedBuffer& operator = (const SharedBuffer&);
  
-        // 16 bytes. must be sized to preserve correct alignment.
+        // Must be sized to preserve correct alignment.
-        mutable int32_t        mRefs;
+        mutable std::atomic<int32_t>        mRefs;
-                size_t         mSize;
+                size_t                      mSize;
-                uint32_t       mReserved[2];
+                uint32_t                    mReserved[2];
 };
 
+static_assert(sizeof(SharedBuffer) % 8 == 0
+        && (sizeof(size_t) > 4 || sizeof(SharedBuffer) == 16),
+        "SharedBuffer has unexpected size");
+
 // ---------------------------------------------------------------------------
 
 const void* SharedBuffer::data() const {
@@ -127,7 +136,7 @@ size_t SharedBuffer::sizeFromData(const void* data) {
 }
 
 bool SharedBuffer::onlyOwner() const {
-    return (mRefs == 1);
+    return (mRefs.load(std::memory_order_acquire) == 1);
 }
 
 }; // namespace android