UT_SmallAlloc.h

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/*
 * PROPRIETARY INFORMATION.  This software is proprietary to
 * Side Effects Software Inc., and is not to be reproduced,
 * transmitted, or disclosed in any way without written permission.
 *
 * NAME:        UT_SmallAlloc.h ( UT Library, C++)
 *
 * COMMENTS:
 */

#ifndef __UT_SmallAlloc__
#define __UT_SmallAlloc__

#include "UT_API.h"
#include "UT_NonCopyable.h"
#include <stddef.h>
#include <string.h>
#include <SYS/SYS_Types.h>

/// UT_SmallAlloc manages the allocation of small (and possibly variable
/// sized) blocks of memory.  Memory is stored in pages of a specified size
/// with one wasted pointer at the beginning of the block storing a link
/// to the next page.  Memory is deallocated on destruction.
class UT_API UT_SmallAlloc
{
public:
     UT_SmallAlloc(size_t page_size = 1024);
    ~UT_SmallAlloc();
   
    UT_NON_COPYABLE(UT_SmallAlloc)
    // Allocates an array with size elements of type T
    template <typename T>
    T                   *allocArray(exint size)
                         { return static_cast<T *>(alloc(size*sizeof(T))); }

    // Creates a copy of the given string
    const char          *allocString(const char *str)
                         {
                             char *copy = allocArray<char>(strlen(str)+1);
                             strcpy(copy, str);
                             return copy;
                         }

    // Raw interface to allocate a block of the given number of bytes
    void                *alloc(size_t bytes);

    // Clear all memory currently allocated by this object
    void                 clear();

    int64                getMemoryUsage() const { return myTotalUsage; }

private:
    void                 init();

private:
    size_t               myPageSize;
    size_t               myHalfPageSize;
    size_t               myHeadOffset;
    void                *myHead;
    void                *myTail;
    size_t               myTotalUsage;
};

#endif