FxMemoryBufferFromLookaside::operator new()

in src/framework/shared/core/fxmemorybufferfromlookaside.cpp [126:190]

• 27 lines of code
• 2 McCabe index (conditional complexity)

FxMemoryBufferFromLookaside::operator new(
    __in size_t Size,
    __in PFX_DRIVER_GLOBALS FxDriverGlobals,
    __inout PVOID ValidMemory,
    __in size_t BufferSize,
    __in PWDF_OBJECT_ATTRIBUTES Attributes
    )
/*++

Routine Description:
    Displacement new operator overload.  Since the lookaside list actually
    allocates the memory block, we just return the block given to us.

Arguments:
    Size - Compiler supplied parameter indicating the
        sizeof(FxMemoryBufferFromLookaside)

    FxDriverGlobals - Driver's globals.

    ValidMemory - Previously allocated block

    BufferSize - The buffer size associated with this object

    Attributes - Description of context.

Return Value:
    ValidMemory pointer value

  --*/
{
    size_t objectSize;

    UNREFERENCED_PARAMETER(Size);

    ASSERT(Size >= sizeof(FxMemoryBufferFromLookaside));

#if (FX_CORE_MODE == FX_CORE_KERNEL_MODE)
    ASSERT(BufferSize < PAGE_SIZE);
    if (BufferSize >= PAGE_SIZE) {
        return NULL;
    }
#endif

    //
    // We round up the object size (via COMPUTE_OBJECT_SIZE) because the object,
    // and the buffer are all in one allocation and the returned memory needs to
    // match the alignment that raw pool follows.
    //
    // Note that FxMemoryBufferFromLookaside is used for buffer less than a page
    // size so downcasting to USHORT (via COMPUTE_OBJECT_SIZE) is safe because
    // size of object plus buffer (<page size) would be smaller than 64K that
    // could fit in USHORT. See comments in FxMemoryObject.hpp for info on
    // various fx memory objects.
    //
    objectSize = COMPUTE_OBJECT_SIZE(sizeof(FxMemoryBufferFromLookaside),
                                     (ULONG) BufferSize);

    return FxObjectAndHandleHeaderInit(
        FxDriverGlobals,
        ValidMemory,
        (USHORT) objectSize,
        Attributes,
        FxObjectTypeExternal
        );
}