UT_StackAlloc.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_StackAlloc.h ( UT Library, C++)
 *
 * COMMENTS:    Wrapper for alloca.
 */

#ifndef __UT_StackAlloc__
#define __UT_StackAlloc__

#include "UT_Assert.h"

#ifdef WIN32
    #include <malloc.h>
#else
    #if defined(LINUX) || defined(MBSD)
        #include <stdlib.h>
    #else
        #include <alloca.h>
    #endif
#endif

// The maximum size of an object that we would allocate on the stack,
// in bytes
#define UT_STACK_LIMIT  131072

// Sentinel values to be stored in the first 4 bytes of the stack data
#define UT_STACK_ALLOCA 100
#define UT_STACK_MALLOC 200

#define UTstackAlloc(size)       (void *)(&((size < UT_STACK_LIMIT) ?    \
    (*((int32 *)::alloca(size+2*sizeof(int32))) = UT_STACK_ALLOCA) : \
    (*((int32 *)::malloc(size+2*sizeof(int32))) = UT_STACK_MALLOC)) + 2)

#define UTstackFree(ptr)                                                \
        {                                                               \
            UT_ASSERT_P(!ptr ||                                         \
                        *((int32 *)ptr - 2) == UT_STACK_MALLOC ||       \
                        *((int32 *)ptr - 2) == UT_STACK_ALLOCA);        \
            if (ptr && (*((int32 *)ptr - 2) == UT_STACK_MALLOC))        \
                ::free(((int32 *)ptr - 2));                             \
        }

#endif