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  1. /*
  2.  * Copyright (c) 2007 Jakub Jermar
  3.  * All rights reserved.
  4.  *
  5.  * Redistribution and use in source and binary forms, with or without
  6.  * modification, are permitted provided that the following conditions
  7.  * are met:
  8.  *
  9.  * - Redistributions of source code must retain the above copyright
  10.  *   notice, this list of conditions and the following disclaimer.
  11.  * - Redistributions in binary form must reproduce the above copyright
  12.  *   notice, this list of conditions and the following disclaimer in the
  13.  *   documentation and/or other materials provided with the distribution.
  14.  * - The name of the author may not be used to endorse or promote products
  15.  *   derived from this software without specific prior written permission.
  16.  *
  17.  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  18.  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  19.  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  20.  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  21.  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  22.  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23.  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24.  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25.  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  26.  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27.  */
  28.  
  29. /** @addtogroup fs
  30.  * @{
  31.  */
  32.  
  33. /**
  34.  * @file    vfs_file.c
  35.  * @brief   Various operations on files have their home in this file.
  36.  */
  37.  
  38. #include <errno.h>
  39. #include <stdlib.h>
  40. #include <string.h>
  41. #include <assert.h>
  42. #include <bool.h>
  43. #include "vfs.h"
  44.  
  45. /**
  46.  * This is a per-connection table of open files.
  47.  * Our assumption is that each client opens only one connection and therefore
  48.  * there is one table of open files per task. However, this may not be the case
  49.  * and the client can open more connections to VFS. In that case, there will be
  50.  * several tables and several file handle name spaces per task. Besides of this,
  51.  * the functionality will stay unchanged. So unless the client knows what it is
  52.  * doing, it should open one connection to VFS only.
  53.  *
  54.  * Allocation of the open files table is deferred until the client makes the
  55.  * first VFS_OPEN operation.
  56.  *
  57.  * This resource being per-connection and, in the first place, per-fibril, we
  58.  * don't need to protect it by a futex.
  59.  */
  60. __thread vfs_file_t **files = NULL;
  61.  
  62. /** Initialize the table of open files. */
  63. bool vfs_files_init(void)
  64. {
  65.     if (!files) {
  66.         files = malloc(MAX_OPEN_FILES * sizeof(vfs_file_t *));
  67.         if (!files)
  68.             return false;
  69.         memset(files, 0, MAX_OPEN_FILES * sizeof(vfs_file_t *));
  70.     }
  71.     return true;
  72. }
  73.  
  74. /** Allocate a file descriptor.
  75.  *
  76.  * @return      First available file descriptor or a negative error
  77.  *          code.
  78.  */
  79. int vfs_fd_alloc(void)
  80. {
  81.     int i;
  82.  
  83.     for (i = 0; i < MAX_OPEN_FILES; i++) {
  84.         if (!files[i]) {
  85.             files[i] = (vfs_file_t *) malloc(sizeof(vfs_file_t));
  86.             if (!files[i])
  87.                 return ENOMEM;
  88.             memset(files[i], 0, sizeof(vfs_file_t));
  89.             futex_initialize(&files[i]->lock, 1);
  90.             vfs_file_addref(files[i]);
  91.             return i;
  92.         }
  93.     }
  94.     return EMFILE;
  95. }
  96.  
  97. /** Release file descriptor.
  98.  *
  99.  * @param fd        File descriptor being released.
  100.  */
  101. void vfs_fd_free(int fd)
  102. {
  103.     assert(fd < MAX_OPEN_FILES);
  104.     assert(files[fd] != NULL);
  105.     vfs_file_delref(files[fd]);
  106.     files[fd] = NULL;
  107. }
  108.  
  109. /** Increment reference count of VFS file structure.
  110.  *
  111.  * @param file      File structure that will have reference count
  112.  *          incremented.
  113.  */
  114. void vfs_file_addref(vfs_file_t *file)
  115. {
  116.     /*
  117.      * File structures are per-connection, so no-one, except the current
  118.      * fibril, should have a reference to them. This is the reason we don't
  119.      * do any synchronization here.
  120.      */
  121.     file->refcnt++;
  122. }
  123.  
  124. /** Decrement reference count of VFS file structure.
  125.  *
  126.  * @param file      File structure that will have reference count
  127.  *          decremented.
  128.  */
  129. void vfs_file_delref(vfs_file_t *file)
  130. {
  131.     if (file->refcnt-- == 1) {
  132.         /*
  133.          * Lost the last reference to a file, need to drop our reference
  134.          * to the underlying VFS node.
  135.          */
  136.         vfs_node_delref(file->node);
  137.         free(file);
  138.     }
  139. }
  140.  
  141. /** Find VFS file structure for a given file descriptor.
  142.  *
  143.  * @param fd        File descriptor.
  144.  *
  145.  * @return      VFS file structure corresponding to fd.
  146.  */
  147. vfs_file_t *vfs_file_get(int fd)
  148. {
  149.     if (fd < MAX_OPEN_FILES)
  150.         return files[fd];
  151.     return NULL;
  152. }
  153.  
  154. /**
  155.  * @}
  156.  */
  157.