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authorfaketruth <faketruth@0a769ca7-a7f5-676a-18bf-c427514a06d6>2011-10-03 21:25:04 +0200
committerfaketruth <faketruth@0a769ca7-a7f5-676a-18bf-c427514a06d6>2011-10-03 21:25:04 +0200
commitaafef187ef856a36c3f8e599afea2dee44f08904 (patch)
treec84762cc768da2800a0f80b902c704e782bd29ef /jsoncpp-src-0.5.0/src/lib_json/json_batchallocator.h
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diff --git a/jsoncpp-src-0.5.0/src/lib_json/json_batchallocator.h b/jsoncpp-src-0.5.0/src/lib_json/json_batchallocator.h
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+#ifndef JSONCPP_BATCHALLOCATOR_H_INCLUDED
+# define JSONCPP_BATCHALLOCATOR_H_INCLUDED
+
+# include <stdlib.h>
+# include <assert.h>
+
+# ifndef JSONCPP_DOC_EXCLUDE_IMPLEMENTATION
+
+namespace Json {
+
+/* Fast memory allocator.
+ *
+ * This memory allocator allocates memory for a batch of object (specified by
+ * the page size, the number of object in each page).
+ *
+ * It does not allow the destruction of a single object. All the allocated objects
+ * can be destroyed at once. The memory can be either released or reused for future
+ * allocation.
+ *
+ * The in-place new operator must be used to construct the object using the pointer
+ * returned by allocate.
+ */
+template<typename AllocatedType
+ ,const unsigned int objectPerAllocation>
+class BatchAllocator
+{
+public:
+ typedef AllocatedType Type;
+
+ BatchAllocator( unsigned int objectsPerPage = 255 )
+ : freeHead_( 0 )
+ , objectsPerPage_( objectsPerPage )
+ {
+// printf( "Size: %d => %s\n", sizeof(AllocatedType), typeid(AllocatedType).name() );
+ assert( sizeof(AllocatedType) * objectPerAllocation >= sizeof(AllocatedType *) ); // We must be able to store a slist in the object free space.
+ assert( objectsPerPage >= 16 );
+ batches_ = allocateBatch( 0 ); // allocated a dummy page
+ currentBatch_ = batches_;
+ }
+
+ ~BatchAllocator()
+ {
+ for ( BatchInfo *batch = batches_; batch; )
+ {
+ BatchInfo *nextBatch = batch->next_;
+ free( batch );
+ batch = nextBatch;
+ }
+ }
+
+ /// allocate space for an array of objectPerAllocation object.
+ /// @warning it is the responsability of the caller to call objects constructors.
+ AllocatedType *allocate()
+ {
+ if ( freeHead_ ) // returns node from free list.
+ {
+ AllocatedType *object = freeHead_;
+ freeHead_ = *(AllocatedType **)object;
+ return object;
+ }
+ if ( currentBatch_->used_ == currentBatch_->end_ )
+ {
+ currentBatch_ = currentBatch_->next_;
+ while ( currentBatch_ && currentBatch_->used_ == currentBatch_->end_ )
+ currentBatch_ = currentBatch_->next_;
+
+ if ( !currentBatch_ ) // no free batch found, allocate a new one
+ {
+ currentBatch_ = allocateBatch( objectsPerPage_ );
+ currentBatch_->next_ = batches_; // insert at the head of the list
+ batches_ = currentBatch_;
+ }
+ }
+ AllocatedType *allocated = currentBatch_->used_;
+ currentBatch_->used_ += objectPerAllocation;
+ return allocated;
+ }
+
+ /// Release the object.
+ /// @warning it is the responsability of the caller to actually destruct the object.
+ void release( AllocatedType *object )
+ {
+ assert( object != 0 );
+ *(AllocatedType **)object = freeHead_;
+ freeHead_ = object;
+ }
+
+private:
+ struct BatchInfo
+ {
+ BatchInfo *next_;
+ AllocatedType *used_;
+ AllocatedType *end_;
+ AllocatedType buffer_[objectPerAllocation];
+ };
+
+ // disabled copy constructor and assignement operator.
+ BatchAllocator( const BatchAllocator & );
+ void operator =( const BatchAllocator &);
+
+ static BatchInfo *allocateBatch( unsigned int objectsPerPage )
+ {
+ const unsigned int mallocSize = sizeof(BatchInfo) - sizeof(AllocatedType)* objectPerAllocation
+ + sizeof(AllocatedType) * objectPerAllocation * objectsPerPage;
+ BatchInfo *batch = static_cast<BatchInfo*>( malloc( mallocSize ) );
+ batch->next_ = 0;
+ batch->used_ = batch->buffer_;
+ batch->end_ = batch->buffer_ + objectsPerPage;
+ return batch;
+ }
+
+ BatchInfo *batches_;
+ BatchInfo *currentBatch_;
+ /// Head of a single linked list within the allocated space of freeed object
+ AllocatedType *freeHead_;
+ unsigned int objectsPerPage_;
+};
+
+
+} // namespace Json
+
+# endif // ifndef JSONCPP_DOC_INCLUDE_IMPLEMENTATION
+
+#endif // JSONCPP_BATCHALLOCATOR_H_INCLUDED
+