# CFReadStream ``` class CFReadStream ``` ## Overview `CFReadStream` provides an interface for reading a byte stream either synchronously or asynchronously. You can create streams that read bytes from a block of memory, a file, or a generic socket. All streams need to be opened, using [`CFReadStreamOpen(_:)`](/documentation/CoreFoundation/CFReadStreamOpen(_:)), before reading. Use [`CFWriteStream`](/documentation/CoreFoundation/CFWriteStream) for writing byte streams. The CFNetwork framework defines an additional type of stream for reading responses to HTTP requests. CFReadStream is “toll-free bridged” with its Cocoa Foundation counterpart, . This means that the Core Foundation type is interchangeable in function or method calls with the bridged Foundation object. Therefore, in a method where you see an `NSInputStream *` parameter, you can pass in a CFReadStreamRef, and in a function where you see a CFReadStreamRef parameter, you can pass in an `NSInputStream` instance. Note, however, that you may have either a delegate or callbacks but not both. See [Toll-Free Bridged Types](https://developer.apple.com/library/archive/documentation/CoreFoundation/Conceptual/CFDesignConcepts/Articles/tollFreeBridgedTypes.html#//apple_ref/doc/uid/TP40010677) for more information on toll-free bridging. ## Topics ### Creating a Read Stream [`CFReadStreamCreateWithBytesNoCopy(_:_:_:_:)`](/documentation/CoreFoundation/CFReadStreamCreateWithBytesNoCopy(_:_:_:_:)) Creates a readable stream for a block of memory. [`CFReadStreamCreateWithFile(_:_:)`](/documentation/CoreFoundation/CFReadStreamCreateWithFile(_:_:)) Creates a readable stream for a file. ### Opening and Closing a Read Stream [`CFReadStreamClose(_:)`](/documentation/CoreFoundation/CFReadStreamClose(_:)) Closes a readable stream. [`CFReadStreamOpen(_:)`](/documentation/CoreFoundation/CFReadStreamOpen(_:)) Opens a stream for reading. ### Reading from a Stream [`CFReadStreamRead(_:_:_:)`](/documentation/CoreFoundation/CFReadStreamRead(_:_:_:)) Reads data from a readable stream. ### Scheduling a Read Stream [`CFReadStreamScheduleWithRunLoop(_:_:_:)`](/documentation/CoreFoundation/CFReadStreamScheduleWithRunLoop(_:_:_:)) Schedules a stream into a run loop. [`CFReadStreamUnscheduleFromRunLoop(_:_:_:)`](/documentation/CoreFoundation/CFReadStreamUnscheduleFromRunLoop(_:_:_:)) Removes a read stream from a given run loop. ### Examining Stream Properties [`CFReadStreamCopyProperty(_:_:)`](/documentation/CoreFoundation/CFReadStreamCopyProperty(_:_:)) Returns the value of a property for a stream. [`CFReadStreamGetBuffer(_:_:_:)`](/documentation/CoreFoundation/CFReadStreamGetBuffer(_:_:_:)) Returns a pointer to a stream’s internal buffer of unread data, if possible. [`CFReadStreamCopyError(_:)`](/documentation/CoreFoundation/CFReadStreamCopyError(_:)) Returns the error associated with a stream. [`CFReadStreamGetError(_:)`](/documentation/CoreFoundation/CFReadStreamGetError(_:)) Returns the error status of a stream. [`CFReadStreamGetStatus(_:)`](/documentation/CoreFoundation/CFReadStreamGetStatus(_:)) Returns the current state of a stream. [`CFReadStreamHasBytesAvailable(_:)`](/documentation/CoreFoundation/CFReadStreamHasBytesAvailable(_:)) Returns a Boolean value that indicates whether a readable stream has data that can be read without blocking. ### Setting Stream Properties [`CFReadStreamSetClient(_:_:_:_:)`](/documentation/CoreFoundation/CFReadStreamSetClient(_:_:_:_:)) Assigns a client to a stream, which receives callbacks when certain events occur. [`CFReadStreamSetProperty(_:_:_:)`](/documentation/CoreFoundation/CFReadStreamSetProperty(_:_:_:)) Sets the value of a property for a stream. ### Getting the CFReadStream Type ID [`CFReadStreamGetTypeID()`](/documentation/CoreFoundation/CFReadStreamGetTypeID()) Returns the type identifier the `CFReadStream` opaque type. ### Callbacks [`CFReadStreamClientCallBack`](/documentation/CoreFoundation/CFReadStreamClientCallBack) Callback invoked when certain types of activity takes place on a readable stream. ### Data Types [`CFStreamClientContext`](/documentation/CoreFoundation/CFStreamClientContext) A structure that contains program-defined data and callbacks with which you can configure a stream’s client behavior. --- 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)