CreateILockBytesOnHGlobal - OLE Programmer's Reference (ole.hlp)

CreateILockBytesOnHGlobal

Returns an OLE-provided implementation of the ILockBytes interface which allows you to build a storage object in memory.

HRESULT CreateILockBytesOnHGlobal(

HGLOBAL hGlobal,	//Memory handle for the byte array object
BOOL fDeleteOnRelease,	//Indicates whether to free memory when the object is released
ILockBytes ** ppLkbyt	//Points to location for pointer to the new byte array object
);

Parameters
hGlobal

Contains the memory handle allocated by the GlobalAlloc function. The handle must be allocated as moveable and nondiscardable. If the handle is to be shared between processes, it must also be allocated as shared. New handles should be allocated with a size of zero. If hGlobal is NULL, the CreateILockBytesOnHGlobal function internally allocates a new shared memory block of size zero.

fDeleteOnRelease

Indicates whether the underlying handle for this byte array object should be automatically freed when the object is released.

ppLkbyt

Points to the location where this method places the pointer for the new byte array object, that is, the new instance of the ILockBytes interface.

Return Values
S_OK

Indicates the ILockBytes instance was created successfully.

E_INVALIDARG

Indicates an invalid value was specified for the hGlobal parameter.

E_OUTOFMEMORY

Indicates not enough memory to create an ILockBytes instance.

Comments
This function creates a byte array object in memory using the OLE-provided implementation of the ILockBytes interface. The returned byte array object can be the basis for a compound file. You can call the StgCreateDocfileOnILockBytes function to build a compound file on top of this byte array object. The ILockBytes instance calls the GlobalReAlloc function to grow the memory block as needed.

The current contents of the memory block are undisturbed by the creation of the new byte array object. After creating the ILockBytes instance, you can use the StgOpenStorageOnILockBytes function to reopen a previously existing storage object already contained in the memory block.

Note If you free the hGlobal memory handle, the byte array object is no longer valid. You must call the ILockBytes::Release method before freeing the memory handle.

The value of the hGlobal parameter can be changed by a subsequent call to the GlobalReAlloc function; thus, you cannot rely on this value after the byte array object is created.