# IOMemoryDescriptor The base class for describing a location in memory. ``` class IOMemoryDescriptor; ``` ## Overview The [`IOMemoryDescriptor`](/documentation/DriverKit/IOMemoryDescriptor) class defines shared behavior for memory-related objects. Use the methods of this class to get information about a memory block and to map a memory block from another process into your driver’s memory space. Don’t create instances of this class directly. When you want to allocate memory for your driver, create an [`IOBufferMemoryDescriptor`](/documentation/DriverKit/IOBufferMemoryDescriptor) instead, which is a concrete implementation of this class. ## Topics ### Configuring the Buffer [`virtual bool init();`](/documentation/DriverKit/IOMemoryDescriptor/init) Initializes the memory descriptor object. [`virtual void free();`](/documentation/DriverKit/IOMemoryDescriptor/free) Performs any final cleanup for the memory descriptor object. ### Getting the Buffer Length [`kern_return_t GetLength(uint64_t *returnLength);`](/documentation/DriverKit/IOMemoryDescriptor/GetLength) Returns the length of the memory block represented by this object. ### Mapping to the Caller’s Address Space [`virtual kern_return_t CreateMapping(uint64_t options, uint64_t address, uint64_t offset, uint64_t length, uint64_t alignment, IOMemoryMap **map);`](/documentation/DriverKit/IOMemoryDescriptor/CreateMapping) Maps the contents of the memory block to the address space of the current process. [Memory Map Options](/documentation/DriverKit/3325558-memory_map_options) Options that describe how to configure a memory-mapped buffer. ### Performing Internal Tasks [`kern_return_t Map(uint64_t options, uint64_t address, uint64_t length, uint64_t alignment, uint64_t *returnAddress, uint64_t *returnLength);`](/documentation/DriverKit/IOMemoryDescriptor/Map) Maps memory internally. ### Type Methods [`static kern_return_t CreateSubMemoryDescriptor(uint64_t memoryDescriptorCreateOptions, uint64_t offset, uint64_t length, IOMemoryDescriptor *ofDescriptor, IOMemoryDescriptor **memory);`](/documentation/DriverKit/IOMemoryDescriptor/CreateSubMemoryDescriptor) [`static kern_return_t CreateWithMemoryDescriptors(uint64_t memoryDescriptorCreateOptions, uint32_t withDescriptorsCount, IOMemoryDescriptor * const withDescriptors[32], IOMemoryDescriptor **memory);`](/documentation/DriverKit/IOMemoryDescriptor/CreateWithMemoryDescriptors) ## Relationships ### Inherited By [`IOBufferMemoryDescriptor`](/documentation/DriverKit/IOBufferMemoryDescriptor) ### Inherits From [`OSObject`](/documentation/DriverKit/OSObject) --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)