forked from OSchip/llvm-project
126 lines
3.8 KiB
C++
126 lines
3.8 KiB
C++
#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
|
|
|