/* GIO - GLib Input, Output and Streaming Library

 *

 * Copyright © 2008 codethink

 * Copyright © 2009 Red Hat, Inc.

 *

 * SPDX-License-Identifier: LGPL-2.1-or-later

 *

 * This library is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public

 * License as published by the Free Software Foundation; either

 * version 2.1 of the License, or (at your option) any later version.

 *

 * This library is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General

 * Public License along with this library; if not, see <http://www.gnu.org/licenses/>.

 *

 * Authors: Ryan Lortie <desrt@desrt.ca>

 *          Alexander Larsson <alexl@redhat.com>

 */

#include "config.h"

#include <glib.h>

#include "glibintl.h"

#include "giostream.h"

#include "gasyncresult.h"

#include "gioprivate.h"

#include "gtask.h"

/**

 * SECTION:giostream

 * @short_description: Base class for implementing read/write streams

 * @include: gio/gio.h

 * @see_also: #GInputStream, #GOutputStream

 *

 * 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).

 *

 * Since: 2.22

 */

enum

{

  PROP_0,

  PROP_INPUT_STREAM,

  PROP_OUTPUT_STREAM,

  PROP_CLOSED

};

struct _GIOStreamPrivate {

  guint closed : 1;

  guint pending : 1;

};

static gboolean g_io_stream_real_close        (GIOStream            *stream,

                 GCancellable         *cancellable,

                 GError              **error);

static void     g_io_stream_real_close_async  (GIOStream            *stream,

                 int                   io_priority,

                 GCancellable         *cancellable,

                 GAsyncReadyCallback   callback,

                 gpointer              user_data);

static gboolean g_io_stream_real_close_finish (GIOStream            *stream,

                 GAsyncResult         *result,

                 GError              **error);

G_DEFINE_ABSTRACT_TYPE_WITH_PRIVATE (GIOStream, g_io_stream, G_TYPE_OBJECT)

static void

g_io_stream_dispose (GObject *object)

{

  GIOStream *stream;

  stream = G_IO_STREAM (object);

  if (!stream->priv->closed)

    g_io_stream_close (stream, NULL, NULL);

  G_OBJECT_CLASS (g_io_stream_parent_class)->dispose (object);

}

static void

g_io_stream_init (GIOStream *stream)

{

  stream->priv = g_io_stream_get_instance_private (stream);

}

static void

g_io_stream_get_property (GObject    *object,

        guint       prop_id,

        GValue     *value,

        GParamSpec *pspec)

{

  GIOStream *stream = G_IO_STREAM (object);

  switch (prop_id)

    {

      case PROP_CLOSED:

        g_value_set_boolean (value, stream->priv->closed);

        break;

      case PROP_INPUT_STREAM:

        g_value_set_object (value, g_io_stream_get_input_stream (stream));

        break;

      case PROP_OUTPUT_STREAM:

        g_value_set_object (value, g_io_stream_get_output_stream (stream));

        break;

      default:

        G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);

    }

}

static void

g_io_stream_class_init (GIOStreamClass *klass)

{

  GObjectClass *gobject_class = G_OBJECT_CLASS (klass);

  gobject_class->dispose = g_io_stream_dispose;

  gobject_class->get_property = g_io_stream_get_property;

  klass->close_fn = g_io_stream_real_close;

  klass->close_async = g_io_stream_real_close_async;

  klass->close_finish = g_io_stream_real_close_finish;

  g_object_class_install_property (gobject_class, PROP_CLOSED,

                                   g_param_spec_boolean ("closed",

                                                         P_("Closed"),

                                                         P_("Is the stream closed"),

                                                         FALSE,

                                                         G_PARAM_READABLE | G_PARAM_STATIC_STRINGS));

  g_object_class_install_property (gobject_class, PROP_INPUT_STREAM,

           g_param_spec_object ("input-stream",

              P_("Input stream"),

              P_("The GInputStream to read from"),

              G_TYPE_INPUT_STREAM,

              G_PARAM_READABLE | G_PARAM_STATIC_STRINGS));

  g_object_class_install_property (gobject_class, PROP_OUTPUT_STREAM,

           g_param_spec_object ("output-stream",

              P_("Output stream"),

              P_("The GOutputStream to write to"),

              G_TYPE_OUTPUT_STREAM,

              G_PARAM_READABLE | G_PARAM_STATIC_STRINGS));

}

/**

 * g_io_stream_is_closed:

 * @stream: a #GIOStream

 *

 * Checks if a stream is closed.

 *

 * Returns: %TRUE if the stream is closed.

 *

 * Since: 2.22

 */

gboolean

g_io_stream_is_closed (GIOStream *stream)

{

  g_return_val_if_fail (G_IS_IO_STREAM (stream), TRUE);

  return stream->priv->closed;

}

/**

 * g_io_stream_get_input_stream:

 * @stream: a #GIOStream

 *

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

 * for reading.

 *

 * Returns: (transfer none): a #GInputStream, owned by the #GIOStream.

 * Do not free.

 *

 * Since: 2.22

 */

GInputStream *

g_io_stream_get_input_stream (GIOStream *stream)

{

  GIOStreamClass *klass;

  klass = G_IO_STREAM_GET_CLASS (stream);

  g_assert (klass->get_input_stream != NULL);

  return klass->get_input_stream (stream);

}

/**

 * g_io_stream_get_output_stream:

 * @stream: a #GIOStream

 *

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

 * writing.

 *

 * Returns: (transfer none): a #GOutputStream, owned by the #GIOStream.

 * Do not free.

 *

 * Since: 2.22

 */

GOutputStream *

g_io_stream_get_output_stream (GIOStream *stream)

{

  GIOStreamClass *klass;

  klass = G_IO_STREAM_GET_CLASS (stream);

  g_assert (klass->get_output_stream != NULL);

  return klass->get_output_stream (stream);

}

/**

 * g_io_stream_has_pending:

 * @stream: a #GIOStream

 *

 * Checks if a stream has pending actions.

 *

 * Returns: %TRUE if @stream has pending actions.

 *

 * Since: 2.22

 **/

gboolean

g_io_stream_has_pending (GIOStream *stream)

{

  g_return_val_if_fail (G_IS_IO_STREAM (stream), FALSE);

  return stream->priv->pending;

}

/**

 * g_io_stream_set_pending:

 * @stream: a #GIOStream

 * @error: a #GError location to store the error occurring, or %NULL to

 *     ignore

 *

 * Sets @stream to have actions pending. If the pending flag is

 * already set or @stream is closed, it will return %FALSE and set

 * @error.

 *

 * Returns: %TRUE if pending was previously unset and is now set.

 *

 * Since: 2.22

 */

gboolean

g_io_stream_set_pending (GIOStream  *stream,

       GError    **error)

{

  g_return_val_if_fail (G_IS_IO_STREAM (stream), FALSE);

  if (stream->priv->closed)

    {

      g_set_error_literal (error, G_IO_ERROR, G_IO_ERROR_CLOSED,

                           _("Stream is already closed"));

      return FALSE;

    }

  if (stream->priv->pending)

    {

      g_set_error_literal (error, G_IO_ERROR, G_IO_ERROR_PENDING,

                           /* Translators: This is an error you get if there is

                            * already an operation running against this stream when

                            * you try to start one */

                           _("Stream has outstanding operation"));

      return FALSE;

    }

  stream->priv->pending = TRUE;

  return TRUE;

}

/**

 * g_io_stream_clear_pending:

 * @stream: a #GIOStream

 *

 * Clears the pending flag on @stream.

 *

 * Since: 2.22

 */

void

g_io_stream_clear_pending (GIOStream *stream)

{

  g_return_if_fail (G_IS_IO_STREAM (stream));

  stream->priv->pending = FALSE;

}

static gboolean

g_io_stream_real_close (GIOStream     *stream,

      GCancellable  *cancellable,

      GError       **error)

{

  gboolean res;

  res = g_output_stream_close (g_io_stream_get_output_stream (stream),

             cancellable, error);

  /* If this errored out, unset error so that we don't report

     further errors, but still do the following ops */

  if (error != NULL && *error != NULL)

    error = NULL;

  res &= g_input_stream_close (g_io_stream_get_input_stream (stream),

             cancellable, error);

  return res;

}

/**

 * g_io_stream_close:

 * @stream: a #GIOStream

 * @cancellable: (nullable): optional #GCancellable object, %NULL to ignore

 * @error: location to store the error occurring, or %NULL to ignore

 *

 * 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.

 *

 * Returns: %TRUE on success, %FALSE on failure

 *

 * Since: 2.22

 */

gboolean

g_io_stream_close (GIOStream     *stream,

       GCancellable  *cancellable,

       GError       **error)

{

  GIOStreamClass *class;

  gboolean res;

  g_return_val_if_fail (G_IS_IO_STREAM (stream), FALSE);

  class = G_IO_STREAM_GET_CLASS (stream);

  if (stream->priv->closed)

    return TRUE;

  if (!g_io_stream_set_pending (stream, error))

    return FALSE;

  if (cancellable)

    g_cancellable_push_current (cancellable);

  res = TRUE;

  if (class->close_fn)

    res = class->close_fn (stream, cancellable, error);

  if (cancellable)

    g_cancellable_pop_current (cancellable);

  stream->priv->closed = TRUE;

  g_io_stream_clear_pending (stream);

  return res;

}

static void

async_ready_close_callback_wrapper (GObject      *source_object,

                                    GAsyncResult *res,

                                    gpointer      user_data)

{

  GIOStream *stream = G_IO_STREAM (source_object);

  GIOStreamClass *klass = G_IO_STREAM_GET_CLASS (stream);

  GTask *task = user_data;

  GError *error = NULL;

  gboolean success;

  stream->priv->closed = TRUE;

  g_io_stream_clear_pending (stream);

  if (g_async_result_legacy_propagate_error (res, &error))

    success = FALSE;

  else

    success = klass->close_finish (stream, res, &error);

  if (error)

    g_task_return_error (task, error);

  else

    g_task_return_boolean (task, success);

  g_object_unref (task);

}

/**

 * g_io_stream_close_async:

 * @stream: a #GIOStream

 * @io_priority: the io priority of the request

 * @cancellable: (nullable): optional cancellable object

 * @callback: (scope async): a #GAsyncReadyCallback

 *   to call when the request is satisfied

 * @user_data: the data to pass to callback function

 *

 * 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.

 *

 * Since: 2.22

 */

void

g_io_stream_close_async (GIOStream           *stream,

       int                  io_priority,

       GCancellable        *cancellable,

       GAsyncReadyCallback  callback,

       gpointer             user_data)

{

  GIOStreamClass *class;

  GError *error = NULL;

  GTask *task;

  g_return_if_fail (G_IS_IO_STREAM (stream));

  task = g_task_new (stream, cancellable, callback, user_data);

  g_task_set_source_tag (task, g_io_stream_close_async);

  if (stream->priv->closed)

    {

      g_task_return_boolean (task, TRUE);

      g_object_unref (task);

      return;

    }

  if (!g_io_stream_set_pending (stream, &error))

    {

      g_task_return_error (task, error);

      g_object_unref (task);

      return;

    }

  class = G_IO_STREAM_GET_CLASS (stream);

  class->close_async (stream, io_priority, cancellable,

          async_ready_close_callback_wrapper, task);

}

/**

 * g_io_stream_close_finish:

 * @stream: a #GIOStream

 * @result: a #GAsyncResult

 * @error: a #GError location to store the error occurring, or %NULL to

 *    ignore

 *

 * Closes a stream.

 *

 * Returns: %TRUE if stream was successfully closed, %FALSE otherwise.

 *

 * Since: 2.22

 */

gboolean

g_io_stream_close_finish (GIOStream     *stream,

        GAsyncResult  *result,

        GError       **error)

{

  g_return_val_if_fail (G_IS_IO_STREAM (stream), FALSE);

  g_return_val_if_fail (g_task_is_valid (result, stream), FALSE);

  return g_task_propagate_boolean (G_TASK (result), error);

}

static void

close_async_thread (GTask        *task,

                    gpointer      source_object,

                    gpointer      task_data,

                    GCancellable *cancellable)

{

  GIOStream *stream = source_object;

  GIOStreamClass *class;

  GError *error = NULL;

  gboolean result;

  class = G_IO_STREAM_GET_CLASS (stream);

  if (class->close_fn)

    {

      result = class->close_fn (stream,

                                g_task_get_cancellable (task),

                                &error);

      if (!result)

        {

          g_task_return_error (task, error);

          return;

        }

    }

  g_task_return_boolean (task, TRUE);

}

typedef struct

{

  GError *error;

  gint pending;

} CloseAsyncData;

static void

stream_close_complete (GObject      *source,

                       GAsyncResult *result,

                       gpointer      user_data)

{

  GTask *task = user_data;

  CloseAsyncData *data;

  data = g_task_get_task_data (task);

  data->pending--;

  if (G_IS_OUTPUT_STREAM (source))

    {

      GError *error = NULL;

      /* Match behaviour with the sync route and give precedent to the

       * error returned from closing the output stream.

       */

      g_output_stream_close_finish (G_OUTPUT_STREAM (source), result, &error);

      if (error)

        {

          if (data->error)

            g_error_free (data->error);

          data->error = error;

        }

    }

  else

    g_input_stream_close_finish (G_INPUT_STREAM (source), result, data->error ? NULL : &data->error);

  if (data->pending == 0)

    {

      if (data->error)

        g_task_return_error (task, data->error);

      else

        g_task_return_boolean (task, TRUE);

      g_slice_free (CloseAsyncData, data);

      g_object_unref (task);

    }

}

static void

g_io_stream_real_close_async (GIOStream           *stream,

            int                  io_priority,

            GCancellable        *cancellable,

            GAsyncReadyCallback  callback,

            gpointer             user_data)

{

  GInputStream *input;

  GOutputStream *output;

  GTask *task;

  task = g_task_new (stream, cancellable, callback, user_data);

  g_task_set_source_tag (task, g_io_stream_real_close_async);

  g_task_set_check_cancellable (task, FALSE);

  g_task_set_priority (task, io_priority);

  input = g_io_stream_get_input_stream (stream);

  output = g_io_stream_get_output_stream (stream);

  if (g_input_stream_async_close_is_via_threads (input) && g_output_stream_async_close_is_via_threads (output))

    {

      /* No sense in dispatching to the thread twice -- just do it all

       * in one go.

       */

      g_task_run_in_thread (task, close_async_thread);

      g_object_unref (task);

    }

  else

    {

      CloseAsyncData *data;

      /* We should avoid dispatching to another thread in case either

       * object that would not do it for itself because it may not be

       * threadsafe.

       */

      data = g_slice_new (CloseAsyncData);

      data->error = NULL;

      data->pending = 2;

      g_task_set_task_data (task, data, NULL);

      g_input_stream_close_async (input, io_priority, cancellable, stream_close_complete, task);

      g_output_stream_close_async (output, io_priority, cancellable, stream_close_complete, task);

    }

}

static gboolean

g_io_stream_real_close_finish (GIOStream     *stream,

             GAsyncResult  *result,

             GError       **error)

{

  g_return_val_if_fail (g_task_is_valid (result, stream), FALSE);

  return g_task_propagate_boolean (G_TASK (result), error);

}

typedef struct

{

  GIOStream *stream1;

  GIOStream *stream2;

  GIOStreamSpliceFlags flags;

  gint io_priority;

  GCancellable *cancellable;

  gulong cancelled_id;

  GCancellable *op1_cancellable;

  GCancellable *op2_cancellable;

  guint completed;

  GError *error;

} SpliceContext;

static void

splice_context_free (SpliceContext *ctx)

{

  g_object_unref (ctx->stream1);

  g_object_unref (ctx->stream2);

  if (ctx->cancellable != NULL)

    g_object_unref (ctx->cancellable);

  g_object_unref (ctx->op1_cancellable);

  g_object_unref (ctx->op2_cancellable);

  g_clear_error (&ctx->error);

  g_slice_free (SpliceContext, ctx);

}

static void

splice_complete (GTask         *task,

                 SpliceContext *ctx)

{

  if (ctx->cancelled_id != 0)

    g_cancellable_disconnect (ctx->cancellable, ctx->cancelled_id);

  ctx->cancelled_id = 0;

  if (ctx->error != NULL)

    {

      g_task_return_error (task, ctx->error);

      ctx->error = NULL;

    }

  else

    g_task_return_boolean (task, TRUE);

}

static void

splice_close_cb (GObject      *iostream,

                 GAsyncResult *res,

                 gpointer      user_data)

{

  GTask *task = user_data;

  SpliceContext *ctx = g_task_get_task_data (task);

  GError *error = NULL;

  g_io_stream_close_finish (G_IO_STREAM (iostream), res, &error);

  ctx->completed++;

  /* Keep the first error that occurred */

  if (error != NULL && ctx->error == NULL)

    ctx->error = error;

  else

    g_clear_error (&error);

  /* If all operations are done, complete now */

  if (ctx->completed == 4)

    splice_complete (task, ctx);

  g_object_unref (task);

}

static void

splice_cb (GObject      *ostream,

           GAsyncResult *res,

           gpointer      user_data)

{

  GTask *task = user_data;

  SpliceContext *ctx = g_task_get_task_data (task);

  GError *error = NULL;

  g_output_stream_splice_finish (G_OUTPUT_STREAM (ostream), res, &error);

  ctx->completed++;

  /* ignore cancellation error if it was not requested by the user */

  if (error != NULL &&

      g_error_matches (error, G_IO_ERROR, G_IO_ERROR_CANCELLED) &&

      (ctx->cancellable == NULL ||

       !g_cancellable_is_cancelled (ctx->cancellable)))

    g_clear_error (&error);

  /* Keep the first error that occurred */

  if (error != NULL && ctx->error == NULL)

    ctx->error = error;

  else

    g_clear_error (&error);

   if (ctx->completed == 1 &&

       (ctx->flags & G_IO_STREAM_SPLICE_WAIT_FOR_BOTH) == 0)

    {

      /* We don't want to wait for the 2nd operation to finish, cancel it */

      g_cancellable_cancel (ctx->op1_cancellable);

      g_cancellable_cancel (ctx->op2_cancellable);

    }

  else if (ctx->completed == 2)

    {

      if (ctx->cancellable == NULL ||

          !g_cancellable_is_cancelled (ctx->cancellable))

        {

          g_cancellable_reset (ctx->op1_cancellable);

          g_cancellable_reset (ctx->op2_cancellable);

        }

      /* Close the IO streams if needed */

      if ((ctx->flags & G_IO_STREAM_SPLICE_CLOSE_STREAM1) != 0)

  {

    g_io_stream_close_async (ctx->stream1,

                                   g_task_get_priority (task),

                                   ctx->op1_cancellable,

                                   splice_close_cb, g_object_ref (task));

  }

      else

        ctx->completed++;

      if ((ctx->flags & G_IO_STREAM_SPLICE_CLOSE_STREAM2) != 0)

  {

    g_io_stream_close_async (ctx->stream2,

                                   g_task_get_priority (task),

                                   ctx->op2_cancellable,

                                   splice_close_cb, g_object_ref (task));

  }

      else

        ctx->completed++;

      /* If all operations are done, complete now */

      if (ctx->completed == 4)

        splice_complete (task, ctx);

    }

  g_object_unref (task);

}

static void

splice_cancelled_cb (GCancellable *cancellable,

                     GTask        *task)

{

  SpliceContext *ctx;

  ctx = g_task_get_task_data (task);

  g_cancellable_cancel (ctx->op1_cancellable);

  g_cancellable_cancel (ctx->op2_cancellable);

}

/**

 * g_io_stream_splice_async:

 * @stream1: a #GIOStream.

 * @stream2: a #GIOStream.

 * @flags: a set of #GIOStreamSpliceFlags.

 * @io_priority: the io priority of the request.

 * @cancellable: (nullable): optional #GCancellable object, %NULL to ignore.

 * @callback: (scope async): a #GAsyncReadyCallback

 *   to call when the request is satisfied

 * @user_data: the data to pass to callback function

 *

 * Asynchronously 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.

 *

 * Since: 2.28

 **/

void

g_io_stream_splice_async (GIOStream            *stream1,

                          GIOStream            *stream2,

                          GIOStreamSpliceFlags  flags,

                          gint                  io_priority,

                          GCancellable         *cancellable,

                          GAsyncReadyCallback   callback,

                          gpointer              user_data)

{

  GTask *task;

  SpliceContext *ctx;

  GInputStream *istream;

  GOutputStream *ostream;

  if (cancellable != NULL && g_cancellable_is_cancelled (cancellable))

    {

      g_task_report_new_error (NULL, callback, user_data,

                               g_io_stream_splice_async,

                               G_IO_ERROR, G_IO_ERROR_CANCELLED,

                               "Operation has been cancelled");

      return;

    }

  ctx = g_slice_new0 (SpliceContext);

  ctx->stream1 = g_object_ref (stream1);

  ctx->stream2 = g_object_ref (stream2);

  ctx->flags = flags;

  ctx->op1_cancellable = g_cancellable_new ();

  ctx->op2_cancellable = g_cancellable_new ();

  ctx->completed = 0;

  task = g_task_new (NULL, cancellable, callback, user_data);

  g_task_set_source_tag (task, g_io_stream_splice_async);

  g_task_set_task_data (task, ctx, (GDestroyNotify) splice_context_free);

  if (cancellable != NULL)

    {

      ctx->cancellable = g_object_ref (cancellable);

      ctx->cancelled_id = g_cancellable_connect (cancellable,

          G_CALLBACK (splice_cancelled_cb), g_object_ref (task),

          g_object_unref);

    }

  istream = g_io_stream_get_input_stream (stream1);

  ostream = g_io_stream_get_output_stream (stream2);

  g_output_stream_splice_async (ostream, istream, G_OUTPUT_STREAM_SPLICE_NONE,

      io_priority, ctx->op1_cancellable, splice_cb,

      g_object_ref (task));

  istream = g_io_stream_get_input_stream (stream2);

  ostream = g_io_stream_get_output_stream (stream1);

  g_output_stream_splice_async (ostream, istream, G_OUTPUT_STREAM_SPLICE_NONE,

      io_priority, ctx->op2_cancellable, splice_cb,

      g_object_ref (task));

  g_object_unref (task);

}

/**

 * g_io_stream_splice_finish:

 * @result: a #GAsyncResult.

 * @error: a #GError location to store the error occurring, or %NULL to

 * ignore.

 *

 * Finishes an asynchronous io stream splice operation.

 *

 * Returns: %TRUE on success, %FALSE otherwise.

 *

 * Since: 2.28

 **/

gboolean

g_io_stream_splice_finish (GAsyncResult  *result,

                           GError       **error)

{

  g_return_val_if_fail (g_task_is_valid (result, NULL), FALSE);

  return g_task_propagate_boolean (G_TASK (result), error);

}