/*++

Copyright (c) 1990  Microsoft Corporation

Module Name:

    MEMORY.C

Abstract:

    This file contains the routines that deal with memory management.

Author:

    Rajen Shah    (rajens)    12-Jul-1991

[Environment:]

    User Mode - Win32, except for NTSTATUS returned by some functions.

Revision History:


--*/


// INCLUDES


#include <eventp.h>


// Implement my own tail-checking, since the system code requires a
// debugging build


//#define TAIL_CHECKING
#ifdef TAIL_CHECKING
#define CHECK_HEAP_TAIL_SIZE 16
#define CHECK_HEAP_TAIL_FILL 0xAB
#endif


PVOID ElfpAllocateBuffer(ULONG Size)
/*++
Routine Description:
    Allocate a buffer of the given size, and return the pointer in BufPtr.

Return Value:
    Pointer to allocated buffer (or NULL).
--*/
{
    PVOID    BufPtr;

#ifdef TAIL_CHECKING

    // Keep the offset of the pattern (so we don't have to have internal
    // knowledge about the granularity of the heap block) and copy a
    // known pattern after the end of the user's block

    BufPtr = (PVOID*)MIDL_user_allocate(Size
                                        + CHECK_HEAP_TAIL_SIZE + sizeof(DWORD));
    *((PDWORD)BufPtr) = Size + sizeof(DWORD);
    (PBYTE)BufPtr += sizeof(DWORD);
    RtlFillMemory((PBYTE)BufPtr + Size,
                  CHECK_HEAP_TAIL_SIZE,
                  CHECK_HEAP_TAIL_FILL);
#else

    BufPtr = (PVOID*)MIDL_user_allocate(Size);

#endif

    return (BufPtr);

}



VOID ElfpFreeBuffer(PVOID BufPtr)

/*++
Routine Description:
    Frees a buffer previously allocated by AllocateBuffer.

Arguments:
    Pointer to buffer.

Return Value:
    NOTHING
--*/
{
#ifdef TAIL_CHECKING
    // Check for NULL when TAIL_CHECKING is enabled since
    // it allows us to avoid checking every pointer that
    // we want to free vs. NULL when we call ElfpFreeBuffer.
    // Note that MIDL_user_free handles NULL.
    if (BufPtr != NULL) {
        DWORD i;
        PBYTE pb;

        // Back up to real start of block
        (PBYTE)BufPtr -= sizeof(DWORD);
        i = *((PDWORD)BufPtr);
        pb = (PBYTE)BufPtr + i;

        for (i = 0; i < CHECK_HEAP_TAIL_SIZE; i++, pb++) {
            if (*pb != CHECK_HEAP_TAIL_FILL) {
                ElfDbgPrint(("[ELF] Heap has been corrupted at 0x%x\n",
                             BufPtr));
                // Make it access violate
                pb = (PBYTE)0;
                *pb = 1;
            }
        }
    }

#endif

    MIDL_user_free(BufPtr);
    return;

}