Virtual Memory: 3.12 Using Virtual Memory: Other VM Utilities

3.11 File-Access Synchronization | Next:

VMCopyVMBlock(), VMSetReloc()

If you would like to duplicate a VM block, or copy it to another file, call VMCopyVMBlock() . This routine is passed three arguments:

The VMFileHandle of the file containing the source block.
The VMBlockHandle of the source block.
The VMFileHandle of the destination file (which may be the same as the source file).

The routine makes a complete duplicate of the source block, copying it to the destination file. It returns the VMBlockHandle of the duplicate block. Note that the duplicate block will almost certainly have a different block handle than the source block. If the block contains a copy of its own handle, you should update it accordingly.

Sometimes you will need to perform special actions whenever loading a block into memory or writing it to the disk. For example, you may store data in a compressed format on the disk, and need to expand it when it's loaded into memory. For this reason, you can set a relocation routine. This routine will be called whenever the following situations occur:

A VM block has just been copied from the disk into memory (routine will be passed the flag VMRT_RELOCATE_AFTER_READ).
A block is about to be written from memory to the disk (routine is passed VMRT_UNRELOCATE_BEFORE_WRITE).
A block in memory has just been written to the disk, but is not being discarded (routine is passed VMRT_RELOCATE_AFTER_WRITE).
A VM block has just been loaded from a resource (routine is passed VMRT_RELOCATE_FROM_RESOURCE). This is called by the relocating object, not by the VM manager.
A VM block is about to be written to a resource (routine is passed VMRT_UNRELOCATE_FROM_RESOURCE). This is called by the unrelocating object, not by the VM manager.

Using the routine VMSetReloc() , you can instruct the VM manager to call your relocation routine whenever appropriate.

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3.11 File-Access Synchronization | Next:

4 VM Chains