chiark / gitweb /
Infrastructure: Split the files into subdirectories.
[mLib] / sys / mdup.h
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b317b99d
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1/* -*-c-*-
2 *
3 * Duplicate multiple files
4 *
5 * (c) 2008 Straylight/Edgeware
6 */
7
8/*----- Licensing notice --------------------------------------------------*
9 *
10 * This program is free software; you can redistribute it and/or modify
11 * it under the terms of the GNU General Public License as published by
12 * the Free Software Foundation; either version 2 of the License, or
13 * (at your option) any later version.
14 *
15 * This program is distributed in the hope that it will be useful,
16 * but WITHOUT ANY WARRANTY; without even the implied warranty of
17 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
18 * GNU General Public License for more details.
19 *
20 * You should have received a copy of the GNU General Public License
21 * along with this program; if not, write to the Free Software Foundation,
22 * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
23 */
24
25#ifndef MDUP_H
26#define MDUP_H
27
28#ifdef __cplusplus
29 extern "C" {
30#endif
31
32/*----- Data structures ---------------------------------------------------*/
33
34typedef struct mdup_fd {
35 int cur; /* Current file descriptor */
36 int want; /* File descriptor wanted */
37} mdup_fd;
38
39/*----- Functions provided ------------------------------------------------*/
40
41/* --- @mdup@ --- *
42 *
43 * Arguments: @mdup_fd *v@ = pointer to @mdup_fd@ vector
44 * @size_t n@ = size of vector
45 *
46 * Returns: Zero if successful, @-1@ on failure.
47 *
48 * Use: Rearranges file descriptors.
49 *
b317b99d
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50 * The vector @v@ consists of a number of @mdup_fd@ structures.
51 * Each `slot' in the table represents a file. The slot's @cur@
52 * member names the current file descriptor for this file; the
53 * @want@ member is the file descriptor we want to use for it.
54 * if you want to keep a file alive but don't care which
55 * descriptor it ends up with, set @want = -1@. Several slots
56 * may specify the same @cur@ descriptor; but they all have to
57 * declare different @want@s (except that several slots may have
58 * @want = -1@.
59 *
60 * On successful exit, the function will have rearranged the
61 * file descriptors as requested. To reflect this, the @cur@
62 * members will all be set to match the (non-@-1@) @want@
63 * members.
64 *
65 * If there is a failure, then some rearrangement may have been
66 * performed and some not; the @cur@ members are set to reflect
67 * which file descriptors are to be used. The old file
68 * descriptors are closed. (This is different from usual @dup@
69 * behaviour, of course, but essential for reliable error
70 * handling.) If you want to keep a particular source file
71 * descriptor open as well as make a new copy then specify two
72 * slots with the same @cur@, one with @want = cur@ and one with
73 * the desired output descriptor.
74 *
75 * This function works correctly even if the desired remappings
76 * contain cycles.
77 */
78
79extern int mdup(mdup_fd */*v*/, size_t /*n*/);
80
81/*----- That's all, folks -------------------------------------------------*/
82
83#ifdef __cplusplus
84 }
85#endif
86
87#endif