GIOStream: GIO Reference Manual

## GIOStream GIOStream — Base class for implementing read/write streams |

## Functions

GInputStream * | g_io_stream_get_input_stream ()
GOutputStream * | g_io_stream_get_output_stream ()
void | g_io_stream_splice_async ()
gboolean | g_io_stream_splice_finish ()
gboolean | g_io_stream_close ()
void | g_io_stream_close_async ()
gboolean | g_io_stream_close_finish ()
gboolean | g_io_stream_is_closed ()
gboolean | g_io_stream_has_pending ()
gboolean | g_io_stream_set_pending ()
void | g_io_stream_clear_pending ()

## Properties

gboolean | closed | Read
GInputStream * | input-stream | Read
GOutputStream * | output-stream | Read

## Types and Values

enum | GIOStreamSpliceFlags
| GIOStream

## Object Hierarchy

        GObject
        ╰── GIOStream
            ├── GFileIOStream
            ├── GSimpleIOStream
            ├── GSocketConnection
            ╰── GTlsConnection

## Includes

    #include <gio/gio.h>

## Description

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

Examples of GIOStream objects are GSocketConnection, which represents a two-way network connection; and GFileIOStream, which represents 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 substreams, so even if the substreams stay alive they will always return `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 but common state in the GIOStream may still be open. However, some streams may support "half-closed" states where one direction of the stream is actually shut down.

Operations on GIOStreams cannot be started while another operation on the GIOStream or its substreams is in progress. Specifically, an application can read from the GInputStream and write to the GOutputStream simultaneously (either in separate threads, or as asynchronous operations in the same thread), but an application cannot start any GIOStream operation while there is a GIOStream, GInputStream or GOutputStream operation in progress, and an application can’t start any GInputStream or GOutputStream operation while there is a GIOStream operation in progress.

This is a product of individual stream operations being associated with a given GMainContext (the thread-default context at the time the operation was started), rather than entire streams being associated with a single GMainContext.

GIO may run operations on GIOStreams from other (worker) threads, and this may be exposed to application code in the behaviour of wrapper streams, such as GBufferedInputStream or GTlsConnection. With such wrapper APIs, application code may only run operations on the base (wrapped) stream when the wrapper stream is idle. Note that the semantics of such operations may not be well-defined due to the state the wrapper stream leaves the base stream in (though they are guaranteed not to crash).

## Functions

### 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.

#### Parameters

stream | a GIOStream |

#### Returns

a GInputStream, owned by the GIOStream. Do not free.

[transfer none]

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.

#### Parameters

stream | a GIOStream |

#### Returns

a GOutputStream, owned by the GIOStream. Do not free.

[transfer none]

Since: 2.22

### g_io_stream_splice_async ()

    void
    g_io_stream_splice_async (GIOStream *stream1,
                              GIOStream *stream2,
                              GIOStreamSpliceFlags flags,
                              int io_priority,
                              GCancellable *cancellable,
                              GAsyncReadyCallback callback,
                              gpointer user_data);

Asyncronously splice the output stream of `stream1` to the input stream of `stream2` , and splice the output stream of `stream2` to the input stream of `stream1` .

When the operation is finished `callback` will be called. You can then call `g_io_stream_splice_finish()` to get the result of the operation.

#### Parameters

stream1 | a GIOStream. |
stream2 | a GIOStream. |
flags | a set of GIOStreamSpliceFlags. |
io_priority | the io priority of the request. |
cancellable | optional GCancellable object, `NULL` to ignore. | [nullable]
callback | a GAsyncReadyCallback. | [scope async]
user_data | user data passed to `callback` . | [closure]

Since: 2.28

### g_io_stream_splice_finish ()

    gboolean
    g_io_stream_splice_finish (GAsyncResult *result,
                               GError **error);

Finishes an asynchronous io stream splice operation.

#### Parameters

result | a GAsyncResult. |
error | a GError location to store the error occurring, or `NULL` to ignore. |

#### Returns

`TRUE` on success, `FALSE` otherwise.

Since: 2.28

### 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 close 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.

#### Parameters

stream | a GIOStream |
cancellable | optional GCancellable object, `NULL` to ignore. | [nullable]
error | location to store the error occurring, 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.

#### Parameters

stream | a GIOStream |
io_priority | the io priority of the request |
cancellable | optional cancellable object. | [nullable]
callback | callback to call when the request is satisfied. | [scope async]
user_data | the data to pass to callback function. | [closure]

Since: 2.22

### g_io_stream_close_finish ()

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

Closes a stream.

#### Parameters

stream | a GIOStream |
result | a GAsyncResult |
error | a GError location to store the error occurring, 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.

#### Parameters

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.

#### Parameters

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` .

#### Parameters

stream | a GIOStream |
error | a GError location to store the error occurring, 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` .

#### Parameters

stream | a GIOStream |

Since: 2.22

## Types and Values

### enum GIOStreamSpliceFlags

GIOStreamSpliceFlags determine how streams should be spliced.

#### Members

G_IO_STREAM_SPLICE_NONE | Do not close either stream. |
G_IO_STREAM_SPLICE_CLOSE_STREAM1 | Close the first stream after the splice. |
G_IO_STREAM_SPLICE_CLOSE_STREAM2 | Close the second stream after the splice. |
G_IO_STREAM_SPLICE_WAIT_FOR_BOTH | Wait for both splice operations to finish before calling the callback. |

Since: 2.28

### GIOStream

    typedef struct _GIOStream GIOStream;

Base class for read-write streams.

## Property Details

### The `“closed”` property

      “closed”                   gboolean

Is the stream closed.

Flags: Read

Default value: FALSE

### The `“input-stream”` property

      “input-stream”             GInputStream *

The GInputStream to read from.

Flags: Read

### The `“output-stream”` property

      “output-stream”            GOutputStream *

The GOutputStream to write to.

Flags: Read

## See Also

GInputStream, GOutputStream