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// Copyright (c) 2012-2014 Konstantin Isakov <ikm@zbackup.org> and ZBackup contributors, see CONTRIBUTORS
// Part of ZBackup. Licensed under GNU GPLv2 or later + OpenSSL, see LICENSE
#ifndef APPENDALLOCATOR_HH_INCLUDED
#define APPENDALLOCATOR_HH_INCLUDED
#include <stdlib.h>
#include <limits>
#include <new>
#include <vector>
/// A simple "add-only" memory allocation mechanism.
class AppendAllocator
{
unsigned alignMask;
unsigned blockSize;
struct Record
{
char * data;
char * prevNextAvailable;
int prevLeftInBlock;
Record( char * data_, char * prevNextAvailable_, int prevLeftInBlock_ ):
data( data_ ), prevNextAvailable( prevNextAvailable_ ),
prevLeftInBlock( prevLeftInBlock_ ) {}
};
std::vector< Record > blocks;
char * nextAvailable;
int leftInBlock; // Can become < 0 due to added alignment
public:
/// blockSize is the amount of bytes allocated for each of the underlying
/// storage blocks. granularity makes sure you allocate objects with
/// the proper alignment. It must be a power of 2
AppendAllocator( unsigned blockSize, unsigned granularity );
~AppendAllocator();
/// Removes all data from the append allocator.
void clear();
/// Allocates a size-sized memory block. The only way to free it is to
/// destroy the whole AppendAllocator. Can throw bad_alloc in an out-of-
/// memory situation
char * allocateBytes( unsigned size );
/// Returns the allocated bytes back. The size must match the size passed
/// to allocateBytes() on the last invocation. Calls to allocateBytes()/
/// returnBytes() must follow the stack order - returnBytes() should undo
/// the previous allocateBytes()
void returnBytes( unsigned size );
/// Allocates memory to hold 'count' objects of T. In essense, it just does
/// multiplication and type casting
template< typename T >
T * allocateObjects( unsigned count )
{ return (T *) allocateBytes( count * sizeof( T ) ); }
/// Returns the allocated objects back
template< typename T >
void returnObjects( unsigned count )
{ returnBytes( count * sizeof( T ) ); }
};
#endif
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