glib2.0/gio/gfileiostream.c

/* GIO - GLib Input, IO and Streaming Library
 *
 * Copyright (C) 2006-2007 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/>.
 *
 * Author: Alexander Larsson <alexl@redhat.com>
 */

#include "config.h"

#include <glib.h>
#include <gfileiostream.h>
#include <gseekable.h>
#include "gasyncresult.h"
#include "gtask.h"
#include "gcancellable.h"
#include "gioerror.h"
#include "gfileoutputstream.h"
#include "glibintl.h"


/**
 * GFileIOStream:
 *
 * `GFileIOStream` provides I/O streams that both read and write to the same
 * file handle.
 *
 * `GFileIOStream` implements [iface@Gio.Seekable], which allows the I/O
 * stream to jump to arbitrary positions in the file and to truncate
 * the file, provided the filesystem of the file supports these
 * operations.
 *
 * To find the position of a file I/O stream, use [method@Gio.Seekable.tell].
 *
 * To find out if a file I/O stream supports seeking, use
 * [method@Gio.Seekable.can_seek]. To position a file I/O stream, use
 * [method@Gio.Seekable.seek]. To find out if a file I/O stream supports
 * truncating, use [method@Gio.Seekable.can_truncate]. To truncate a file I/O
 * stream, use [method@Gio.Seekable.truncate].
 *
 * The default implementation of all the `GFileIOStream` operations
 * and the implementation of [iface@Gio.Seekable] just call into the same
 * operations on the output stream.
 *
 * Since: 2.22
 **/

static void       g_file_io_stream_seekable_iface_init    (GSeekableIface       *iface);
static goffset    g_file_io_stream_seekable_tell          (GSeekable            *seekable);
static gboolean   g_file_io_stream_seekable_can_seek      (GSeekable            *seekable);
static gboolean   g_file_io_stream_seekable_seek          (GSeekable            *seekable,
							   goffset               offset,
							   GSeekType             type,
							   GCancellable         *cancellable,
							   GError              **error);
static gboolean   g_file_io_stream_seekable_can_truncate  (GSeekable            *seekable);
static gboolean   g_file_io_stream_seekable_truncate      (GSeekable            *seekable,
							   goffset               offset,
							   GCancellable         *cancellable,
							   GError              **error);
static void       g_file_io_stream_real_query_info_async  (GFileIOStream    *stream,
							   const char           *attributes,
							   int                   io_priority,
							   GCancellable         *cancellable,
							   GAsyncReadyCallback   callback,
							   gpointer              user_data);
static GFileInfo *g_file_io_stream_real_query_info_finish (GFileIOStream    *stream,
							   GAsyncResult         *result,
							   GError              **error);

struct _GFileIOStreamPrivate {
  GAsyncReadyCallback outstanding_callback;
};

G_DEFINE_TYPE_WITH_CODE (GFileIOStream, g_file_io_stream, G_TYPE_IO_STREAM,
                         G_ADD_PRIVATE (GFileIOStream)
			 G_IMPLEMENT_INTERFACE (G_TYPE_SEEKABLE,
						g_file_io_stream_seekable_iface_init))

static void
g_file_io_stream_seekable_iface_init (GSeekableIface *iface)
{
  iface->tell = g_file_io_stream_seekable_tell;
  iface->can_seek = g_file_io_stream_seekable_can_seek;
  iface->seek = g_file_io_stream_seekable_seek;
  iface->can_truncate = g_file_io_stream_seekable_can_truncate;
  iface->truncate_fn = g_file_io_stream_seekable_truncate;
}

static void
g_file_io_stream_init (GFileIOStream *stream)
{
  stream->priv = g_file_io_stream_get_instance_private (stream);
}

/**
 * g_file_io_stream_query_info:
 * @stream: a #GFileIOStream.
 * @attributes: a file attribute query string.
 * @cancellable: (nullable): optional #GCancellable object, %NULL to ignore.
 * @error: a #GError, %NULL to ignore.
 *
 * Queries a file io stream for the given @attributes.
 * This function blocks while querying the stream. For the asynchronous
 * version of this function, see g_file_io_stream_query_info_async().
 * While the stream is blocked, the stream will set the pending flag
 * internally, and any other operations on the stream will fail with
 * %G_IO_ERROR_PENDING.
 *
 * Can fail if the stream was already closed (with @error being set to
 * %G_IO_ERROR_CLOSED), the stream has pending operations (with @error being
 * set to %G_IO_ERROR_PENDING), or if querying info is not supported for
 * the stream's interface (with @error being set to %G_IO_ERROR_NOT_SUPPORTED). I
 * all cases of failure, %NULL will be returned.
 *
 * 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 set, and %NULL will
 * be returned.
 *
 * Returns: (transfer full): a #GFileInfo for the @stream, or %NULL on error.
 *
 * Since: 2.22
 **/
GFileInfo *
g_file_io_stream_query_info (GFileIOStream      *stream,
			     const char             *attributes,
			     GCancellable           *cancellable,
			     GError                **error)
{
  GFileIOStreamClass *class;
  GIOStream *io_stream;
  GFileInfo *info;

  g_return_val_if_fail (G_IS_FILE_IO_STREAM (stream), NULL);

  io_stream = G_IO_STREAM (stream);

  if (!g_io_stream_set_pending (io_stream, error))
    return NULL;

  info = NULL;

  if (cancellable)
    g_cancellable_push_current (cancellable);

  class = G_FILE_IO_STREAM_GET_CLASS (stream);
  if (class->query_info)
    info = class->query_info (stream, attributes, cancellable, error);
  else
    g_set_error_literal (error, G_IO_ERROR, G_IO_ERROR_NOT_SUPPORTED,
                         _("Stream doesn’t support query_info"));

  if (cancellable)
    g_cancellable_pop_current (cancellable);

  g_io_stream_clear_pending (io_stream);

  return info;
}

static void
async_ready_callback_wrapper (GObject *source_object,
			      GAsyncResult *res,
			      gpointer      user_data)
{
  GFileIOStream *stream = G_FILE_IO_STREAM (source_object);

  g_io_stream_clear_pending (G_IO_STREAM (stream));
  if (stream->priv->outstanding_callback)
    (*stream->priv->outstanding_callback) (source_object, res, user_data);
  g_object_unref (stream);
}

/**
 * g_file_io_stream_query_info_async:
 * @stream: a #GFileIOStream.
 * @attributes: a file attribute query string.
 * @io_priority: the [I/O priority](iface.AsyncResult.html#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 queries the @stream for a #GFileInfo. When completed,
 * @callback will be called with a #GAsyncResult which can be used to
 * finish the operation with g_file_io_stream_query_info_finish().
 *
 * For the synchronous version of this function, see
 * g_file_io_stream_query_info().
 *
 * Since: 2.22
 **/
void
g_file_io_stream_query_info_async (GFileIOStream     *stream,
					  const char           *attributes,
					  int                   io_priority,
					  GCancellable         *cancellable,
					  GAsyncReadyCallback   callback,
					  gpointer              user_data)
{
  GFileIOStreamClass *klass;
  GIOStream *io_stream;
  GError *error = NULL;

  g_return_if_fail (G_IS_FILE_IO_STREAM (stream));

  io_stream = G_IO_STREAM (stream);

  if (!g_io_stream_set_pending (io_stream, &error))
    {
      g_task_report_error (stream, callback, user_data,
                           g_file_io_stream_query_info_async,
                           error);
      return;
    }

  klass = G_FILE_IO_STREAM_GET_CLASS (stream);

  stream->priv->outstanding_callback = callback;
  g_object_ref (stream);
  klass->query_info_async (stream, attributes, io_priority, cancellable,
                           async_ready_callback_wrapper, user_data);
}

/**
 * g_file_io_stream_query_info_finish:
 * @stream: a #GFileIOStream.
 * @result: a #GAsyncResult.
 * @error: a #GError, %NULL to ignore.
 *
 * Finalizes the asynchronous query started
 * by g_file_io_stream_query_info_async().
 *
 * Returns: (transfer full): A #GFileInfo for the finished query.
 *
 * Since: 2.22
 **/
GFileInfo *
g_file_io_stream_query_info_finish (GFileIOStream     *stream,
				    GAsyncResult         *result,
				    GError              **error)
{
  GFileIOStreamClass *class;

  g_return_val_if_fail (G_IS_FILE_IO_STREAM (stream), NULL);
  g_return_val_if_fail (G_IS_ASYNC_RESULT (result), NULL);

  if (g_async_result_legacy_propagate_error (result, error))
    return NULL;
  else if (g_async_result_is_tagged (result, g_file_io_stream_query_info_async))
    return g_task_propagate_pointer (G_TASK (result), error);

  class = G_FILE_IO_STREAM_GET_CLASS (stream);
  return class->query_info_finish (stream, result, error);
}

/**
 * g_file_io_stream_get_etag:
 * @stream: a #GFileIOStream.
 *
 * Gets the entity tag for the file when it has been written.
 * This must be called after the stream has been written
 * and closed, as the etag can change while writing.
 *
 * Returns: (nullable) (transfer full): the entity tag for the stream.
 *
 * Since: 2.22
 **/
char *
g_file_io_stream_get_etag (GFileIOStream  *stream)
{
  GFileIOStreamClass *class;
  GIOStream *io_stream;
  char *etag;

  g_return_val_if_fail (G_IS_FILE_IO_STREAM (stream), NULL);

  io_stream = G_IO_STREAM (stream);

  if (!g_io_stream_is_closed (io_stream))
    {
      g_warning ("stream is not closed yet, can't get etag");
      return NULL;
    }

  etag = NULL;

  class = G_FILE_IO_STREAM_GET_CLASS (stream);
  if (class->get_etag)
    etag = class->get_etag (stream);

  return etag;
}

static goffset
g_file_io_stream_tell (GFileIOStream  *stream)
{
  GFileIOStreamClass *class;
  goffset offset;

  g_return_val_if_fail (G_IS_FILE_IO_STREAM (stream), 0);

  class = G_FILE_IO_STREAM_GET_CLASS (stream);

  offset = 0;
  if (class->tell)
    offset = class->tell (stream);

  return offset;
}

static goffset
g_file_io_stream_seekable_tell (GSeekable *seekable)
{
  return g_file_io_stream_tell (G_FILE_IO_STREAM (seekable));
}

static gboolean
g_file_io_stream_can_seek (GFileIOStream  *stream)
{
  GFileIOStreamClass *class;
  gboolean can_seek;

  g_return_val_if_fail (G_IS_FILE_IO_STREAM (stream), FALSE);

  class = G_FILE_IO_STREAM_GET_CLASS (stream);

  can_seek = FALSE;
  if (class->seek)
    {
      can_seek = TRUE;
      if (class->can_seek)
	can_seek = class->can_seek (stream);
    }

  return can_seek;
}

static gboolean
g_file_io_stream_seekable_can_seek (GSeekable *seekable)
{
  return g_file_io_stream_can_seek (G_FILE_IO_STREAM (seekable));
}

static gboolean
g_file_io_stream_seek (GFileIOStream  *stream,
		       goffset             offset,
		       GSeekType           type,
		       GCancellable       *cancellable,
		       GError            **error)
{
  GFileIOStreamClass *class;
  GIOStream *io_stream;
  gboolean res;

  g_return_val_if_fail (G_IS_FILE_IO_STREAM (stream), FALSE);

  io_stream = G_IO_STREAM (stream);
  class = G_FILE_IO_STREAM_GET_CLASS (stream);

  if (!class->seek)
    {
      g_set_error_literal (error, G_IO_ERROR, G_IO_ERROR_NOT_SUPPORTED,
                           _("Seek not supported on stream"));
      return FALSE;
    }

  if (!g_io_stream_set_pending (io_stream, error))
    return FALSE;

  if (cancellable)
    g_cancellable_push_current (cancellable);

  res = class->seek (stream, offset, type, cancellable, error);

  if (cancellable)
    g_cancellable_pop_current (cancellable);

  g_io_stream_clear_pending (io_stream);

  return res;
}

static gboolean
g_file_io_stream_seekable_seek (GSeekable  *seekable,
				    goffset     offset,
				    GSeekType   type,
				    GCancellable  *cancellable,
				    GError    **error)
{
  return g_file_io_stream_seek (G_FILE_IO_STREAM (seekable),
				offset, type, cancellable, error);
}

static gboolean
g_file_io_stream_can_truncate (GFileIOStream  *stream)
{
  GFileIOStreamClass *class;
  gboolean can_truncate;

  g_return_val_if_fail (G_IS_FILE_IO_STREAM (stream), FALSE);

  class = G_FILE_IO_STREAM_GET_CLASS (stream);

  can_truncate = FALSE;
  if (class->truncate_fn)
    {
      can_truncate = TRUE;
      if (class->can_truncate)
	can_truncate = class->can_truncate (stream);
    }

  return can_truncate;
}

static gboolean
g_file_io_stream_seekable_can_truncate (GSeekable  *seekable)
{
  return g_file_io_stream_can_truncate (G_FILE_IO_STREAM (seekable));
}

static gboolean
g_file_io_stream_truncate (GFileIOStream  *stream,
			   goffset             size,
			   GCancellable       *cancellable,
			   GError            **error)
{
  GFileIOStreamClass *class;
  GIOStream *io_stream;
  gboolean res;

  g_return_val_if_fail (G_IS_FILE_IO_STREAM (stream), FALSE);

  io_stream = G_IO_STREAM (stream);
  class = G_FILE_IO_STREAM_GET_CLASS (stream);

  if (!class->truncate_fn)
    {
      g_set_error_literal (error, G_IO_ERROR, G_IO_ERROR_NOT_SUPPORTED,
                           _("Truncate not supported on stream"));
      return FALSE;
    }

  if (!g_io_stream_set_pending (io_stream, error))
    return FALSE;

  if (cancellable)
    g_cancellable_push_current (cancellable);

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

  if (cancellable)
    g_cancellable_pop_current (cancellable);

  g_io_stream_clear_pending (io_stream);

  return res;
}

static gboolean
g_file_io_stream_seekable_truncate (GSeekable     *seekable,
				    goffset        size,
				    GCancellable  *cancellable,
				    GError       **error)
{
  return g_file_io_stream_truncate (G_FILE_IO_STREAM (seekable),
					size, cancellable, error);
}
/*****************************************************
 *   Default implementations based on output stream  *
 *****************************************************/

static goffset
g_file_io_stream_real_tell (GFileIOStream    *stream)
{
  GOutputStream *out;
  GSeekable *seekable;

  out = g_io_stream_get_output_stream (G_IO_STREAM (stream));
  seekable = G_SEEKABLE (out);

  return g_seekable_tell (seekable);
}

static gboolean
g_file_io_stream_real_can_seek (GFileIOStream    *stream)
{
  GOutputStream *out;
  GSeekable *seekable;

  out = g_io_stream_get_output_stream (G_IO_STREAM (stream));
  seekable = G_SEEKABLE (out);

  return g_seekable_can_seek (seekable);
}

static gboolean
g_file_io_stream_real_seek (GFileIOStream    *stream,
			    goffset           offset,
			    GSeekType         type,
			    GCancellable     *cancellable,
			    GError          **error)
{
  GOutputStream *out;
  GSeekable *seekable;

  out = g_io_stream_get_output_stream (G_IO_STREAM (stream));
  seekable = G_SEEKABLE (out);

  return g_seekable_seek (seekable, offset, type, cancellable, error);
}

static  gboolean
g_file_io_stream_real_can_truncate (GFileIOStream    *stream)
{
  GOutputStream *out;
  GSeekable *seekable;

  out = g_io_stream_get_output_stream (G_IO_STREAM (stream));
  seekable = G_SEEKABLE (out);

  return g_seekable_can_truncate (seekable);
}

static gboolean
g_file_io_stream_real_truncate_fn (GFileIOStream    *stream,
				   goffset               size,
				   GCancellable         *cancellable,
				   GError              **error)
{
  GOutputStream *out;
  GSeekable *seekable;

  out = g_io_stream_get_output_stream (G_IO_STREAM (stream));
  seekable = G_SEEKABLE (out);

  return g_seekable_truncate (seekable, size, cancellable, error);
}

static char *
g_file_io_stream_real_get_etag (GFileIOStream    *stream)
{
  GOutputStream *out;
  GFileOutputStream *file_out;

  out = g_io_stream_get_output_stream (G_IO_STREAM (stream));
  file_out = G_FILE_OUTPUT_STREAM (out);

  return g_file_output_stream_get_etag (file_out);
}

static GFileInfo *
g_file_io_stream_real_query_info (GFileIOStream    *stream,
				  const char           *attributes,
				  GCancellable         *cancellable,
				  GError              **error)
{
  GOutputStream *out;
  GFileOutputStream *file_out;

  out = g_io_stream_get_output_stream (G_IO_STREAM (stream));
  file_out = G_FILE_OUTPUT_STREAM (out);

  return g_file_output_stream_query_info (file_out,
					  attributes, cancellable, error);
}

typedef struct {
  GObject *object;
  GAsyncReadyCallback callback;
  gpointer user_data;
} AsyncOpWrapper;

static AsyncOpWrapper *
async_op_wrapper_new (gpointer object,
		      GAsyncReadyCallback callback,
		      gpointer user_data)
{
  AsyncOpWrapper *data;

  data = g_new0 (AsyncOpWrapper, 1);
  data->object = g_object_ref (object);
  data->callback = callback;
  data->user_data = user_data;

  return data;
}

static void
async_op_wrapper_callback (GObject *source_object,
			   GAsyncResult *res,
			   gpointer user_data)
{
  AsyncOpWrapper *data  = user_data;
  data->callback (data->object, res, data->user_data);
  g_object_unref (data->object);
  g_free (data);
}

static void
g_file_io_stream_real_query_info_async (GFileIOStream     *stream,
					const char           *attributes,
					int                   io_priority,
					GCancellable         *cancellable,
					GAsyncReadyCallback   callback,
					gpointer              user_data)
{
  GOutputStream *out;
  GFileOutputStream *file_out;
  AsyncOpWrapper *data;

  out = g_io_stream_get_output_stream (G_IO_STREAM (stream));
  file_out = G_FILE_OUTPUT_STREAM (out);

  data = async_op_wrapper_new (stream, callback, user_data);
  g_file_output_stream_query_info_async (file_out,
					 attributes, io_priority,
					 cancellable, async_op_wrapper_callback, data);
}

static GFileInfo *
g_file_io_stream_real_query_info_finish (GFileIOStream     *stream,
					 GAsyncResult      *res,
					 GError           **error)
{
  GOutputStream *out;
  GFileOutputStream *file_out;

  out = g_io_stream_get_output_stream (G_IO_STREAM (stream));
  file_out = G_FILE_OUTPUT_STREAM (out);

  return g_file_output_stream_query_info_finish (file_out, res, error);
}

static void
g_file_io_stream_class_init (GFileIOStreamClass *klass)
{
  klass->tell = g_file_io_stream_real_tell;
  klass->can_seek = g_file_io_stream_real_can_seek;
  klass->seek = g_file_io_stream_real_seek;
  klass->can_truncate = g_file_io_stream_real_can_truncate;
  klass->truncate_fn = g_file_io_stream_real_truncate_fn;
  klass->query_info = g_file_io_stream_real_query_info;
  klass->query_info_async = g_file_io_stream_real_query_info_async;
  klass->query_info_finish = g_file_io_stream_real_query_info_finish;
  klass->get_etag = g_file_io_stream_real_get_etag;
}