# dispatch_source_get_data Returns pending data for the dispatch source. ``` extern uintptr_t dispatch_source_get_data(dispatch_source_t source); ``` ## Parameters `source` This parameter cannot be `NULL`. ## Discussion ### Return Value The return value should be interpreted according to the type of the dispatch source, and can be one of the following: - [`DISPATCH_SOURCE_TYPE_DATA_ADD`](/documentation/Dispatch/DISPATCH_SOURCE_TYPE_DATA_ADD): application-defined data - [`DISPATCH_SOURCE_TYPE_DATA_OR`](/documentation/Dispatch/DISPATCH_SOURCE_TYPE_DATA_OR): application-defined data - [`DISPATCH_SOURCE_TYPE_MACH_SEND`](/documentation/Dispatch/DISPATCH_SOURCE_TYPE_MACH_SEND): `Dispatch Source Mach Send Event Flags` - [`DISPATCH_SOURCE_TYPE_MACH_RECV`](/documentation/Dispatch/DISPATCH_SOURCE_TYPE_MACH_RECV): not applicable - [`DISPATCH_SOURCE_TYPE_PROC`](/documentation/Dispatch/DISPATCH_SOURCE_TYPE_PROC): `Dispatch Source Process Event Flags` - [`DISPATCH_SOURCE_TYPE_READ`](/documentation/Dispatch/DISPATCH_SOURCE_TYPE_READ): estimated bytes available to read - [`DISPATCH_SOURCE_TYPE_SIGNAL`](/documentation/Dispatch/DISPATCH_SOURCE_TYPE_SIGNAL): number of signals delivered since the last handler invocation - [`DISPATCH_SOURCE_TYPE_TIMER`](/documentation/Dispatch/DISPATCH_SOURCE_TYPE_TIMER): number of times the timer has fired since the last handler invocation - [`DISPATCH_SOURCE_TYPE_VNODE`](/documentation/Dispatch/DISPATCH_SOURCE_TYPE_VNODE): `Dispatch Source Vnode Event Flags` - `Dispatch Source Memory Pressure Event Flags`: estimated buffer space available ## Discussion Call this function from within the event handler block. The result of calling this function outside of the event handler callback is undefined. --- 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)