mdw@git.distorted.org.uk Git - mLib/blob - sys/mdup.h

   1 /* -*-c-*-
   2  *
   3  * Duplicate multiple files
   4  *
   5  * (c) 2008 Straylight/Edgeware
   6  */
   7
   8 /*----- Licensing notice --------------------------------------------------*
   9  *
  10  * This file is part of the mLib utilities library.
  11  *
  12  * mLib is free software; you can redistribute it and/or modify
  13  * it under the terms of the GNU Library General Public License as
  14  * published by the Free Software Foundation; either version 2 of the
  15  * License, or (at your option) any later version.
  16  *
  17  * mLib is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20  * GNU Library General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU Library General Public
  23  * License along with mLib; if not, write to the Free
  24  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  25  * MA 02111-1307, USA.
  26  */
  27
  28 #ifndef MDUP_H
  29 #define MDUP_H
  30
  31 #ifdef __cplusplus
  32   extern "C" {
  33 #endif
  34
  35 /*----- Data structures ---------------------------------------------------*/
  36
  37 typedef struct mdup_fd {
  38   int cur;                              /* Current file descriptor */
  39   int want;                             /* File descriptor wanted */
  40 } mdup_fd;
  41
  42 /*----- Functions provided ------------------------------------------------*/
  43
  44 /* --- @mdup@ --- *
  45  *
  46  * Arguments:   @mdup_fd *v@ = pointer to @mdup_fd@ vector
  47  *              @size_t n@ = size of vector
  48  *
  49  * Returns:     Zero if successful, @-1@ on failure.
  50  *
  51  * Use:         Rearranges file descriptors.
  52  *
  53  *              The vector @v@ consists of a number of @mdup_fd@ structures.
  54  *              Each `slot' in the table represents a file.  The slot's @cur@
  55  *              member names the current file descriptor for this file; the
  56  *              @want@ member is the file descriptor we want to use for it.
  57  *              if you want to keep a file alive but don't care which
  58  *              descriptor it ends up with, set @want = -1@.  Several slots
  59  *              may specify the same @cur@ descriptor; but they all have to
  60  *              declare different @want@s (except that several slots may have
  61  *              @want = -1@.
  62  *
  63  *              On successful exit, the function will have rearranged the
  64  *              file descriptors as requested.  To reflect this, the @cur@
  65  *              members will all be set to match the (non-@-1@) @want@
  66  *              members.
  67  *
  68  *              If there is a failure, then some rearrangement may have been
  69  *              performed and some not; the @cur@ members are set to reflect
  70  *              which file descriptors are to be used.  The old file
  71  *              descriptors are closed.  (This is different from usual @dup@
  72  *              behaviour, of course, but essential for reliable error
  73  *              handling.)  If you want to keep a particular source file
  74  *              descriptor open as well as make a new copy then specify two
  75  *              slots with the same @cur@, one with @want = cur@ and one with
  76  *              the desired output descriptor.
  77  *
  78  *              This function works correctly even if the desired remappings
  79  *              contain cycles.
  80  */
  81
  82 extern int mdup(mdup_fd */*v*/, size_t /*n*/);
  83
  84 /*----- That's all, folks -------------------------------------------------*/
  85
  86 #ifdef __cplusplus
  87   }
  88 #endif
  89
  90 #endif