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1 : : /* GIO - GLib Input, Output and Streaming Library
2 : : *
3 : : * Copyright (C) 2006-2007 Red Hat, Inc.
4 : : *
5 : : * SPDX-License-Identifier: LGPL-2.1-or-later
6 : : *
7 : : * This library is free software; you can redistribute it and/or
8 : : * modify it under the terms of the GNU Lesser General Public
9 : : * License as published by the Free Software Foundation; either
10 : : * version 2.1 of the License, or (at your option) any later version.
11 : : *
12 : : * This library is distributed in the hope that it will be useful,
13 : : * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 : : * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 : : * Lesser General Public License for more details.
16 : : *
17 : : * You should have received a copy of the GNU Lesser General
18 : : * Public License along with this library; if not, see <http://www.gnu.org/licenses/>.
19 : : *
20 : : * Author: Alexander Larsson <alexl@redhat.com>
21 : : */
22 : :
23 : : #include "config.h"
24 : : #include "gseekable.h"
25 : : #include "glibintl.h"
26 : :
27 : :
28 : : /**
29 : : * GSeekable:
30 : : *
31 : : * `GSeekable` is implemented by streams (implementations of
32 : : * [class@Gio.InputStream] or [class@Gio.OutputStream]) that support seeking.
33 : : *
34 : : * Seekable streams largely fall into two categories: resizable and
35 : : * fixed-size.
36 : : *
37 : : * `GSeekable` on fixed-sized streams is approximately the same as POSIX
38 : : * [`lseek()`](man:lseek(2)) on a block device (for example: attempting to seek
39 : : * past the end of the device is an error). Fixed streams typically cannot be
40 : : * truncated.
41 : : *
42 : : * `GSeekable` on resizable streams is approximately the same as POSIX
43 : : * [`lseek()`](man:lseek(2)) on a normal file. Seeking past the end and writing
44 : : * data will usually cause the stream to resize by introducing zero bytes.
45 : : **/
46 : :
47 : : typedef GSeekableIface GSeekableInterface;
48 : 52238 : G_DEFINE_INTERFACE (GSeekable, g_seekable, G_TYPE_OBJECT)
49 : :
50 : : static void
51 : 158 : g_seekable_default_init (GSeekableInterface *iface)
52 : : {
53 : 158 : }
54 : :
55 : : /**
56 : : * g_seekable_tell:
57 : : * @seekable: a #GSeekable.
58 : : *
59 : : * Tells the current position within the stream.
60 : : *
61 : : * Returns: the (positive or zero) offset from the beginning of the
62 : : * buffer, zero if the target is not seekable.
63 : : **/
64 : : goffset
65 : 8430 : g_seekable_tell (GSeekable *seekable)
66 : : {
67 : : GSeekableIface *iface;
68 : :
69 : 8430 : g_return_val_if_fail (G_IS_SEEKABLE (seekable), 0);
70 : :
71 : 8430 : iface = G_SEEKABLE_GET_IFACE (seekable);
72 : :
73 : 8430 : return (* iface->tell) (seekable);
74 : : }
75 : :
76 : : /**
77 : : * g_seekable_can_seek:
78 : : * @seekable: a #GSeekable.
79 : : *
80 : : * Tests if the stream supports the #GSeekableIface.
81 : : *
82 : : * Returns: %TRUE if @seekable can be seeked. %FALSE otherwise.
83 : : **/
84 : : gboolean
85 : 1038 : g_seekable_can_seek (GSeekable *seekable)
86 : : {
87 : : GSeekableIface *iface;
88 : :
89 : 1038 : g_return_val_if_fail (G_IS_SEEKABLE (seekable), FALSE);
90 : :
91 : 1038 : iface = G_SEEKABLE_GET_IFACE (seekable);
92 : :
93 : 1038 : return (* iface->can_seek) (seekable);
94 : : }
95 : :
96 : : /**
97 : : * g_seekable_seek:
98 : : * @seekable: a #GSeekable.
99 : : * @offset: a #goffset.
100 : : * @type: a #GSeekType.
101 : : * @cancellable: (nullable): optional #GCancellable object, %NULL to ignore.
102 : : * @error: a #GError location to store the error occurring, or %NULL to
103 : : * ignore.
104 : : *
105 : : * Seeks in the stream by the given @offset, modified by @type.
106 : : *
107 : : * Attempting to seek past the end of the stream will have different
108 : : * results depending on if the stream is fixed-sized or resizable. If
109 : : * the stream is resizable then seeking past the end and then writing
110 : : * will result in zeros filling the empty space. Seeking past the end
111 : : * of a resizable stream and reading will result in EOF. Seeking past
112 : : * the end of a fixed-sized stream will fail.
113 : : *
114 : : * Any operation that would result in a negative offset will fail.
115 : : *
116 : : * If @cancellable is not %NULL, then the operation can be cancelled by
117 : : * triggering the cancellable object from another thread. If the operation
118 : : * was cancelled, the error %G_IO_ERROR_CANCELLED will be returned.
119 : : *
120 : : * Returns: %TRUE if successful. If an error
121 : : * has occurred, this function will return %FALSE and set @error
122 : : * appropriately if present.
123 : : **/
124 : : gboolean
125 : 7429 : g_seekable_seek (GSeekable *seekable,
126 : : goffset offset,
127 : : GSeekType type,
128 : : GCancellable *cancellable,
129 : : GError **error)
130 : : {
131 : : GSeekableIface *iface;
132 : :
133 : 7429 : g_return_val_if_fail (G_IS_SEEKABLE (seekable), FALSE);
134 : :
135 : 7429 : iface = G_SEEKABLE_GET_IFACE (seekable);
136 : :
137 : 7429 : return (* iface->seek) (seekable, offset, type, cancellable, error);
138 : : }
139 : :
140 : : /**
141 : : * g_seekable_can_truncate:
142 : : * @seekable: a #GSeekable.
143 : : *
144 : : * Tests if the length of the stream can be adjusted with
145 : : * g_seekable_truncate().
146 : : *
147 : : * Returns: %TRUE if the stream can be truncated, %FALSE otherwise.
148 : : **/
149 : : gboolean
150 : 8 : g_seekable_can_truncate (GSeekable *seekable)
151 : : {
152 : : GSeekableIface *iface;
153 : :
154 : 8 : g_return_val_if_fail (G_IS_SEEKABLE (seekable), FALSE);
155 : :
156 : 8 : iface = G_SEEKABLE_GET_IFACE (seekable);
157 : :
158 : 8 : return (* iface->can_truncate) (seekable);
159 : : }
160 : :
161 : : /**
162 : : * g_seekable_truncate: (virtual truncate_fn)
163 : : * @seekable: a #GSeekable.
164 : : * @offset: new length for @seekable, in bytes.
165 : : * @cancellable: (nullable): optional #GCancellable object, %NULL to ignore.
166 : : * @error: a #GError location to store the error occurring, or %NULL to
167 : : * ignore.
168 : : *
169 : : * Sets the length of the stream to @offset. If the stream was previously
170 : : * larger than @offset, the extra data is discarded. If the stream was
171 : : * previously shorter than @offset, it is extended with NUL ('\0') bytes.
172 : : *
173 : : * If @cancellable is not %NULL, then the operation can be cancelled by
174 : : * triggering the cancellable object from another thread. If the operation
175 : : * was cancelled, the error %G_IO_ERROR_CANCELLED will be returned. If an
176 : : * operation was partially finished when the operation was cancelled the
177 : : * partial result will be returned, without an error.
178 : : *
179 : : * Returns: %TRUE if successful. If an error
180 : : * has occurred, this function will return %FALSE and set @error
181 : : * appropriately if present.
182 : : **/
183 : : gboolean
184 : 15 : g_seekable_truncate (GSeekable *seekable,
185 : : goffset offset,
186 : : GCancellable *cancellable,
187 : : GError **error)
188 : : {
189 : : GSeekableIface *iface;
190 : :
191 : 15 : g_return_val_if_fail (G_IS_SEEKABLE (seekable), FALSE);
192 : :
193 : 15 : iface = G_SEEKABLE_GET_IFACE (seekable);
194 : :
195 : 15 : return (* iface->truncate_fn) (seekable, offset, cancellable, error);
196 : : }
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