windows-server-2003/com/rpc/midl/support/freelist.cxx

/*************************************************************************/
/**             Copyright(c) Microsoft Corp., 1993-1999                 **/
/*************************************************************************/
/**************************************************************************
File            FreeListMgr.cxx
Title       :Get and Put functions for the MIDL compiler
History     :
    13-Apr-94   GregJen Created from freelist.hxx
**************************************************************************/

#pragma warning ( disable : 4201 )  // Unnamed struct/union
#pragma warning ( disable : 4514 )  // Unreferenced inline function

/************************************************************************* 
 ** includes                                                
 *************************************************************************/

#include "freelist.hxx"
#include <windef.h>         // REVIEW: Just give up and include windows.h?
#include <basetsd.h>

// checked compiler has list checking
#ifndef NDEBUG

// turn on the below flag to get checked freelist
#define LIST_CHECK

#endif

/************************************************************************* 
 ** definitions
 *************************************************************************/

// The user should see allocated memory aligned at LONG_PTR alignment.
// The allocator returns us memory with this alignment so make sure the
// signature preserves it.
typedef LONG_PTR HeapSignature;


#define USED_SIGNATURE( pMgr, pNode )       \
                 ( ((HeapSignature) pMgr) % ((HeapSignature) pNode) )

#define FREE_SIGNATURE( pMgr, pNode )       \
                 ( ((HeapSignature) pMgr) - ((HeapSignature) pNode) )
        
void * 
FreeListMgr::Get (size_t size)
    {
    void *  pEntry;
#ifdef LIST_CHECK
    HeapSignature   *   pSignature;
#endif
 
    /* Count this call (even if it fails).
     */

#ifndef NDEBUG
    GetCount++;
#endif

    /* Make sure the "size" requested is the same as the previous 
     * requests.
     */

    MIDL_ASSERT (size == element_size);

    /* Get an entry from the free-list, if the free-list is not empty */

    if (pHead != NULL)
        {
        pEntry  = pHead;
        pHead   = pHead->next;
#ifdef LIST_CHECK
        // check to make sure the entry is really OK
        // signature is before entry pointer
        // signature of free nodes is ( &mgr - &node )
        // signature of used nodes is ( &mgr % &node )
        pSignature = ((HeapSignature *)pEntry)-1;

        MIDL_ASSERT( *pSignature == FREE_SIGNATURE( this, pEntry ) );

        *pSignature = USED_SIGNATURE( this, pEntry );
        memset( pEntry, 0xB3, size );
#endif
        return (void *) pEntry;
        }

    /* Get it from the allocator, since the free-list is empty */

    else
        {
#ifdef LIST_CHECK
        pSignature  = (HeapSignature *)
                            AllocateOnceNew( size + sizeof( *pSignature ) );
        pEntry  = ( (char *) pSignature ) + sizeof( *pSignature );

        *pSignature = USED_SIGNATURE( this, pEntry );
        memset( pEntry, 0xB2, size );
        return pEntry;
#else
        return AllocateOnceNew(size);
#endif
        }

    } /* Get */

    /*********************************************************************/ 
    // This routine "releases" the given element, by putting it on
    // the free-list for later re-use.  The given element, must be 
    // the same size as the elements provided by the "Get" function.
    /*********************************************************************/ 
        
void    
FreeListMgr::Put (void * pEntry)
    {
#ifdef LIST_CHECK
    HeapSignature   *   pSignature;
#endif
    // Count this call.

#ifndef NDEBUG
    PutCount++;
#endif

    // Put the given element on the head of the free-list.

#ifdef LIST_CHECK
    // check to make sure the entry is really OK
    // signature is before entry pointer
    // signature of free nodes is ( &mgr - &node )
    // signature of used nodes is ( &mgr % &node )
    pSignature = ((HeapSignature *)pEntry)-1;

    MIDL_ASSERT( *pSignature == USED_SIGNATURE( this, pEntry ) );

    *pSignature = FREE_SIGNATURE( this, pEntry );

    memset( pEntry, 0xA1, element_size );
#endif
    ( (FreeListType *) pEntry ) -> next = pHead;
    pHead = (FreeListType *) pEntry;


    }; /* Put */




#ifdef example



// 
// Example of use...
//
// copy the following into a class definition and replace the X's with 
// the name of the class
//

/*********************************************************************/ 
// here is the free list manager for a particular class.  it should
// NOT be inherited unless the derived classes have no extra data members.
// 
// Otherwise, the derived classes should have their own new and delete
// elsewhere.
/*********************************************************************/ 
private:

    static
    FreeListMgr         MyFreeList( sizeof( X ) );
    

public:

/*********************************************************************/ 
// Return a new element of the specified size.
// 
// The FreeListMgr "Get" routine is used, so that the element may be
// retrieved from a free-list, if possible, and extra get-memory calls
// can thus be avoided.  
/*********************************************************************/ 

X *
operator new (size_t size)
    {
    return (MyFreeList.Get (size));
    } 

/*********************************************************************/ 
// Release an element allocated by the "New" routine.
//
/*********************************************************************/ 
void operator delete (X* pX)
    {
    MyFreeList.Put (pX);
    } 

#endif // example