| Derived from | |
| Framework | CoreFoundation/CoreFoundation.h |
| Declared in | CFStream.h |
CFWriteStream provides an interface for writing a byte stream either synchronously or asynchronously. You can create streams that write bytes to a block of memory, a file, or a generic socket. All streams need to be opened, using CFWriteStreamOpen, before writing.
Use CFReadStream for reading byte streams, and for the functions, such as CFStreamCreatePairWithSocketToHost, that create socket streams).
CFWriteStream is “toll-free bridged” with its Cocoa Foundation counterpart, NSOutputStream. 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 NSOutputStream * parameter, you can pass in a CFWriteStreamRef, and in a function where you see a CFWriteStreamRef parameter, you can pass in an NSOutputStream instance. Note, however, that you may have either a delegate or callbacks but not both. See Interchangeable Data Types for more information on toll-free bridging.
CFWriteStreamCanAcceptBytes
CFWriteStreamCopyProperty
CFWriteStreamCopyError
CFWriteStreamGetError
CFWriteStreamGetStatus
Returns whether a writable stream can accept new data without blocking.
Boolean CFWriteStreamCanAcceptBytes ( CFWriteStreamRef stream );
The stream to examine.
true if data can be written to stream without blocking, false otherwise. If stream cannot tell if data can be written without actually trying to write the data, this function returns true.
CFStream.h
Closes a writable stream.
void CFWriteStreamClose ( CFWriteStreamRef stream );
The stream to close.
This function terminates the flow of bytes and releases any system resources required by the stream. The stream is removed from any run loops in which it was scheduled. Once closed, the stream cannot be reopened.
CFStream.hReturns the error associated with a stream.
CFErrorRef CFWriteStreamCopyError ( CFReadStreamRef stream );
The stream to examine.
A CFError object that describes the current problem with stream, or NULL if there is no error. Ownership follows the Create Rule.
CFStream.h
Returns the value of a property for a stream.
CFTypeRef CFWriteStreamCopyProperty ( CFWriteStreamRef stream, CFStringRef propertyName );
The stream to examine.
The name of the stream property to obtain. The available properties for standard Core Foundation streams are listed in “Stream Properties.”
The value of the property propertyName. Ownership follows the Create Rule.
Each type of stream can define a set of properties that either describe or configure individual streams. A property can be any interesting information about a stream. Examples include the headers from an HTTP transmission, the expected number of bytes, file permission information, and so on. Use CFWriteStreamSetProperty to modify the value of a property, although some properties are read-only.
CFStream.h
Creates a writable stream for a growable block of memory.
CFWriteStreamRef CFWriteStreamCreateWithAllocatedBuffers ( CFAllocatorRef alloc, CFAllocatorRef bufferAllocator );
The allocator to use to allocate memory for the new object. Pass NULL or kCFAllocatorDefault to use the current default allocator.
The allocator to use to allocate memory for the stream’s memory buffers. Pass NULL or kCFAllocatorDefault to use the current default allocator.
A new write stream. Ownership follows the Create Rule.
New buffers are allocated using bufferAllocator as bytes are written to the stream. At any point, you can recover the bytes thus far written by asking for the property kCFStreamPropertyDataWritten with CFWriteStreamCopyProperty.
You must open the stream, using CFWriteStreamOpen, before writing to it.
CFStream.h
Creates a writable stream for a fixed-size block of memory.
CFWriteStreamRef CFWriteStreamCreateWithBuffer ( CFAllocatorRef alloc, UInt8 *buffer, CFIndex bufferCapacity );
The allocator to use to allocate memory for the new object. Pass NULL or kCFAllocatorDefault to use the current default allocator.
The memory buffer into which to write data. This buffer must exist for the lifetime of the stream.
The size of buffer and the maximum number of bytes that can be written.
A new write stream, or NULL on failure. Ownership follows the Create Rule.
When buffer is filled after writing bufferCapacity bytes, the stream is exhausted and its status becomes kCFStreamStatusAtEnd.
You must open the stream, using CFWriteStreamOpen, before writing to it.
CFStream.h
Creates a writable stream for a file.
CFWriteStreamRef CFWriteStreamCreateWithFile ( CFAllocatorRef alloc, CFURLRef fileURL );
The allocator to use to allocate memory for the new object. Pass NULL or kCFAllocatorDefault to use the current default allocator.
The URL of the file to which to write. The URL must use a file scheme.
The new write stream, or NULL on failure. Ownership follows the Create Rule.
The stream overwrites an existing file unless you set the kCFStreamPropertyAppendToFile to kCFBooleanTrue with CFWriteStreamSetProperty, in which case the stream appends data to the file.
You must open the stream, using CFWriteStreamOpen, before writing to it.
CFStream.h
Returns the error status of a stream. (Deprecated. Use CFWriteStreamCopyError instead.)
CFStreamError CFWriteStreamGetError ( CFWriteStreamRef stream );
The stream to examine.
The error status of stream returned in a CFStreamError structure.
CFStream.h
Returns the current state of a stream.
CFStreamStatus CFWriteStreamGetStatus ( CFWriteStreamRef stream );
The stream to examine.
The current state of stream. See CFStreamStatus for the list of possible states.
CFStream.h
Returns the type identifier of all CFWriteStream objects.
CFTypeID CFWriteStreamGetTypeID ( void );
The type identifier for the CFWriteStream opaque type.
CFStream.h
Opens a stream for writing.
Boolean CFWriteStreamOpen ( CFWriteStreamRef stream );
The stream to open.
true if stream was successfully opened, false otherwise. If stream is not in the kCFStreamStatusNotOpen state, this function returns false.
Opening a stream causes it to reserve all the system resources it requires. If the stream can open in the background without blocking, this function always returns true. To learn when a background open operation completes, you can either schedule the stream into a run loop with CFWriteStreamScheduleWithRunLoop and wait for the stream’s client (set with CFWriteStreamSetClient) to be notified or you can poll the stream using CFWriteStreamGetStatus, waiting for a status of kCFStreamStatusOpen or kCFStreamStatusError.
CFStream.h
Schedules a stream into a run loop.
void CFWriteStreamScheduleWithRunLoop ( CFWriteStreamRef stream, CFRunLoopRef runLoop, CFStringRef runLoopMode );
The stream to schedule.
The run loop in which to schedule stream.
The run loop mode of runLoop in which to schedule stream.
After scheduling stream into a run loop, its client (set with CFWriteStreamSetClient) is notified when various events happen with the stream, such as when it finishes opening, when it can accept new bytes, and when an error occurs. A stream can be scheduled into multiple run loops and run loop modes. Use CFWriteStreamUnscheduleFromRunLoop to later remove stream from the run loop.
CFStream.h
Assigns a client to a stream, which receives callbacks when certain events occur.
Boolean CFWriteStreamSetClient ( CFWriteStreamRef stream, CFOptionFlags streamEvents, CFWriteStreamClientCallBack clientCB, CFStreamClientContext *clientContext );
The stream to modify.
The set of events for which the client should receive callbacks. The events are listed in CFStreamEventType. If you pass kCFStreamEventNone, the current client for stream is removed.
The client callback function to call when one of the events requested in streamEvents occurs. If NULL, the current client for stream is removed.
A structure holding contextual information for the stream client. The function copies the information out of the structure, so the memory pointed to by clientContext does not need to persist beyond the function call. If NULL, the current client for stream is removed.
true if the stream supports asynchronous notification, false otherwise.
To avoid polling and blocking, you can register a client to hear about interesting events that occur on a stream. Only one client per stream is allowed; registering a new client replaces the previous one.
Once you have set a client, you need to schedule the stream in a run loop using CFWriteStreamScheduleWithRunLoop so that the client can receive the asynchronous notifications. You can schedule each stream in multiple run loops (for example, if you are using a thread pool). It is the caller's responsibility to ensure that at least one of the scheduled run loops is being run, otherwise the callback cannot be called.
Although all Core Foundation streams currently support asynchronous notification, future stream types may not. If a stream does not support asynchronous notification, this function returns false. Typically, such streams never block for device I/O (for example, a stream writing to memory) and don’t benefit from asynchronous notification.
CFStream.hSets the value of a property for a stream.
Boolean CFWriteStreamSetProperty ( CFWriteStreamRef stream, CFStringRef propertyName, CFTypeRef propertyValue );
The stream to modify.
The name of the property to set. The available properties for standard Core Foundation streams are listed in “Stream Properties.”
The value to which to set the property propertyName for stream. The allowed data type of the value depends on the property being set.
true if stream recognizes and accepts the given property-value pair, false otherwise.
Each type of stream can define a set of properties that either describe or configure individual streams. A property can be any interesting information about a stream. Examples include the headers from an HTTP transmission, the expected number of bytes, file permission information, and so on. Properties that can be set configure the behavior of the stream and may be modifiable only at particular times, such as before the stream has been opened. (In fact, you should assume that you can set properties only before opening the stream, unless otherwise noted.) To read the value of a property use CFWriteStreamCopyProperty, although some properties are write-only.
CFStream.h
Removes a stream from a particular run loop.
void CFWriteStreamUnscheduleFromRunLoop ( CFWriteStreamRef stream, CFRunLoopRef runLoop, CFStringRef runLoopMode );
The stream to remove.
The run loop from which to remove stream.
The run loop mode of runLoop from which to remove stream.
CFStream.h
Writes data to a writable stream.
CFIndex CFWriteStreamWrite ( CFWriteStreamRef stream, const UInt8 *buffer, CFIndex bufferLength );
The stream to which to write.
The buffer holding the data to write.
The number of bytes from buffer to write.
The number of bytes successfully written, 0 if the stream has been filled to capacity (for fixed-length streams), or -1 if either the stream is not open or an error occurs.
If stream is in the process of opening, this function waits until it has completed. If the stream is not full, this call blocks until at least one byte is written; it does not block until all the bytes in buffer is written. To avoid blocking, call this function only if CFWriteStreamCanAcceptBytes returns true or after the stream’s client (set with CFWriteStreamSetClient) is notified of a kCFStreamEventCanAcceptBytes event.
CFStream.hCallback invoked when certain types of activity takes place on a writable stream.
typedef void (*CFWriteStreamClientCallBack) ( CFWriteStreamRef stream, CFStreamEventType eventType, void *clientCallBackInfo );
If you name your function MyCallBack, you would declare it like this:
void MyCallBack ( CFWriteStreamRef stream, CFStreamEventType eventType, void *clientCallBackInfo );
The stream that experienced the event eventType.
The event that caused the callback to be called. The possible events are listed in “Stream Events.”.
The info member of the CFStreamClientContext structure that was used when setting the client for stream.
This callback is called only for the events requested when setting the client with CFWriteStreamSetClient.
CFStream.hA reference to a writable stream object.
typedef struct __CFWriteStream *CFWriteStreamRef;
CFStream.h
Last updated: 2007-05-03
