## GIOStream

GIOStream — Base class for implementing read/write streams

## Synopsis

    #include <gio/gio.h>

                        GIOStream;
    GInputStream *      g_io_stream_get_input_stream        (GIOStream *stream);
    GOutputStream *     g_io_stream_get_output_stream       (GIOStream *stream);
    gboolean            g_io_stream_close                   (GIOStream *stream,
                                                             GCancellable *cancellable,
                                                             GError **error);
    void                g_io_stream_close_async             (GIOStream *stream,
                                                             int io_priority,
                                                             GCancellable *cancellable,
                                                             GAsyncReadyCallback callback,
                                                             gpointer user_data);
    gboolean            g_io_stream_close_finish            (GIOStream *stream,
                                                             GAsyncResult *result,
                                                             GError **error);
    gboolean            g_io_stream_is_closed               (GIOStream *stream);
    gboolean            g_io_stream_has_pending             (GIOStream *stream);
    gboolean            g_io_stream_set_pending             (GIOStream *stream,
                                                             GError **error);
    void                g_io_stream_clear_pending           (GIOStream *stream);

## Object Hierarchy

      GObject
       +----GIOStream
             +----GFileIOStream
             +----GSocketConnection

## Properties

      "closed"                   gboolean              : Read / Write
      "input-stream"             GInputStream*         : Read
      "output-stream"            GOutputStream*        : Read

## Description

GIOStream represents an object that has both read and write streams. Generally the two streams acts as separate input and output streams, but they share some common resources and state. For instance, for seekable streams they may use the same position in both streams.

Examples of GIOStream objects are GSocketConnection which represents a two-way network connection, and GFileIOStream which represent a file handle opened in read-write mode.

To do the actual reading and writing you need to get the substreams with `g_io_stream_get_input_stream()` and `g_io_stream_get_output_stream()`.

The GIOStream object owns the input and the output streams, not the other way around, so keeping the substreams alive will not keep the GIOStream object alive. If the GIOStream object is freed it will be closed, thus closing the substream, so even if the substreams stay alive they will always just return a `G_IO_ERROR_CLOSED` for all operations.

To close a stream use `g_io_stream_close()` which will close the common stream object and also the individual substreams. You can also close the substreams themselves. In most cases this only marks the substream as closed, so further I/O on it fails. However, some streams may support "half-closed" states where one direction of the stream is actually shut down.

## Details

### GIOStream

    typedef struct _GIOStream GIOStream;

Base class for read-write streams.

### g_io_stream_get_input_stream ()

    GInputStream *      g_io_stream_get_input_stream        (GIOStream *stream);

Gets the input stream for this object. This is used for reading.

`stream` : | a GIOStream
Returns : | a GInputStream, owned by the GIOStream. Do not free.

Since 2.22

### g_io_stream_get_output_stream ()

    GOutputStream *     g_io_stream_get_output_stream       (GIOStream *stream);

Gets the output stream for this object. This is used for writing.

`stream` : | a GIOStream
Returns : | a GOutputStream, owned by the GIOStream. Do not free.

Since 2.22

### g_io_stream_close ()

    gboolean            g_io_stream_close                   (GIOStream *stream,
                                                             GCancellable *cancellable,
                                                             GError **error);

Closes the stream, releasing resources related to it. This will also closes the individual input and output streams, if they are not already closed.

Once the stream is closed, all other operations will return `G_IO_ERROR_CLOSED`. Closing a stream multiple times will not return an error.

Closing a stream will automatically flush any outstanding buffers in the stream.

Streams will be automatically closed when the last reference is dropped, but you might want to call this function to make sure resources are released as early as possible.

Some streams might keep the backing store of the stream (e.g. a file descriptor) open after the stream is closed. See the documentation for the individual stream for details.

On failure the first error that happened will be reported, but the close operation will finish as much as possible. A stream that failed to close will still return `G_IO_ERROR_CLOSED` for all operations. Still, it is important to check and report the error to the user, otherwise there might be a loss of data as all data might not be written.

If `cancellable` is not NULL, then the operation can be cancelled by triggering the cancellable object from another thread. If the operation was cancelled, the error `G_IO_ERROR_CANCELLED` will be returned. Cancelling a close will still leave the stream closed, but some streams can use a faster close that doesn't block to e.g. check errors.

The default implementation of this method just calls close on the individual input/output streams.

`stream` : | a GIOStream
`cancellable` : | optional GCancellable object, `NULL` to ignore
`error` : | location to store the error occuring, or `NULL` to ignore
Returns : | `TRUE` on success, `FALSE` on failure

Since 2.22

### g_io_stream_close_async ()

    void                g_io_stream_close_async             (GIOStream *stream,
                                                             int io_priority,
                                                             GCancellable *cancellable,
                                                             GAsyncReadyCallback callback,
                                                             gpointer user_data);

Requests an asynchronous close of the stream, releasing resources related to it. When the operation is finished `callback` will be called. You can then call `g_io_stream_close_finish()` to get the result of the operation.

For behaviour details see `g_io_stream_close()`.

The asynchronous methods have a default fallback that uses threads to implement asynchronicity, so they are optional for inheriting classes. However, if you override one you must override all.

`stream` : | a GIOStream
`io_priority` : | the io priority of the request
`cancellable` : | optional cancellable object
`callback` : | callback to call when the request is satisfied
`user_data` : | the data to pass to callback function

Since 2.22

### g_io_stream_close_finish ()

    gboolean            g_io_stream_close_finish            (GIOStream *stream,
                                                             GAsyncResult *result,
                                                             GError **error);

Closes a stream.

`stream` : | a GIOStream
`result` : | a GAsyncResult
`error` : | a GError location to store the error occuring, or `NULL` to ignore
Returns : | `TRUE` if stream was successfully closed, `FALSE` otherwise.

Since 2.22

### g_io_stream_is_closed ()

    gboolean            g_io_stream_is_closed               (GIOStream *stream);

Checks if a stream is closed.

`stream` : | a GIOStream
Returns : | `TRUE` if the stream is closed.

Since 2.22

### g_io_stream_has_pending ()

    gboolean            g_io_stream_has_pending             (GIOStream *stream);

Checks if a stream has pending actions.

`stream` : | a GIOStream
Returns : | `TRUE` if `stream` has pending actions.

Since 2.22

### g_io_stream_set_pending ()

    gboolean            g_io_stream_set_pending             (GIOStream *stream,
                                                             GError **error);

Sets `stream` to have actions pending. If the pending flag is already set or `stream` is closed, it will return `FALSE` and set `error`.

`stream` : | a GIOStream
`error` : | a GError location to store the error occuring, or `NULL` to ignore
Returns : | `TRUE` if pending was previously unset and is now set.

Since 2.22

### g_io_stream_clear_pending ()

    void                g_io_stream_clear_pending           (GIOStream *stream);

Clears the pending flag on `stream`.

`stream` : | a GIOStream

Since 2.22

## Property Details

### The `"closed"` property

      "closed"                   gboolean              : Read / Write

Is the stream closed.

Default value: FALSE

### The `"input-stream"` property

      "input-stream"             GInputStream*         : Read

The GInputStream to read from.

### The `"output-stream"` property

      "output-stream"            GOutputStream*        : Read

The GOutputStream to write to.

## See Also

#GInputStream, GOutputStream