withPersistentMemoryDescriptor

Copy constructor that generates a new memory descriptor if the backing memory for the same task's virtual address and length has changed.

Declaration

static IOMemoryDescriptor * withPersistentMemoryDescriptor(
 IOMemoryDescriptor *originalMD); 

Parameters

originalMD

The memory descriptor to be duplicated.

Return Value

Either the original memory descriptor with an additional retain or a new memory descriptor, 0 for a bad original memory descriptor or some other resource shortage.

Overview

If the original memory descriptor's address and length is still backed by the same real memory, i.e. the user hasn't deallocated and the reallocated memory at the same address then the original memory descriptor is returned with a additional reference. Otherwise we build a totally new memory descriptor with the same characteristics as the previous one but with a new view of the vm. Note not legal to call this function with anything except an IOGeneralMemoryDescriptor that was created with the kIOMemoryPersistent option.

See Also

Miscellaneous

- complete

Complete processing of the memory after an I/O transfer finishes.

- createMappingInTask

Maps a IOMemoryDescriptor into a task.

- getDirection

Accessor to get the direction the memory descriptor was created with.

- getLength

Accessor to get the length of the memory descriptor (over all its ranges).

- getPageCounts

Retrieve the number of resident and/or dirty pages encompassed by an IOMemoryDescriptor.

- getPhysicalAddress

Return the physical address of the first byte in the memory.

- getPhysicalSegment

Break a memory descriptor into its physically contiguous segments.

- getTag

Accessor to the retrieve the tag for the memory descriptor.

- initWithOptions

Master initialiser for all variants of memory descriptors. For a more complete description see IOMemoryDescriptor::withOptions.

- map

Maps a IOMemoryDescriptor into the kernel map.

- performOperation

Perform an operation on the memory descriptor's memory.

- prepare

Prepare the memory for an I/O transfer.

- readBytes

Copy data from the memory descriptor's buffer to the specified buffer.

- setMapping

Establishes an already existing mapping.

- setPurgeable

Control the purgeable status of a memory descriptors memory.

- setTag

Set the tag for the memory descriptor.

- withAddress

Create an IOMemoryDescriptor to describe one virtual range of the kernel task.

- withAddressRange

Create an IOMemoryDescriptor to describe one virtual range of the specified map.

- withAddressRanges

Create an IOMemoryDescriptor to describe one or more virtual ranges.

- withOptions

Master initialiser for all variants of memory descriptors.

- withPhysicalAddress

Create an IOMemoryDescriptor to describe one physical range.

- writeBytes

Copy data to the memory descriptor's buffer from the specified buffer.