daily update

audofeed-device-backend/jsoncpp/json_batchallocator.h

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+// Copyright 2007-2010 Baptiste Lepilleur
+// Distributed under MIT license, or public domain if desired and
+// recognized in your jurisdiction.
+// See file LICENSE for detail or copy at http://jsoncpp.sourceforge.net/LICENSE
+
+#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:
+  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
+// vim: et ts=2 sts=2 sw=2 tw=0