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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 <fibril.h>
  44. #include <fibril_sync.h>
  45. #include "vfs.h"
  46.  
  47. /**
  48.  * This is a per-connection table of open files.
  49.  * Our assumption is that each client opens only one connection and therefore
  50.  * there is one table of open files per task. However, this may not be the case
  51.  * and the client can open more connections to VFS. In that case, there will be
  52.  * several tables and several file handle name spaces per task. Besides of this,
  53.  * the functionality will stay unchanged. So unless the client knows what it is
  54.  * doing, it should open one connection to VFS only.
  55.  *
  56.  * Allocation of the open files table is deferred until the client makes the
  57.  * first VFS_OPEN operation.
  58.  *
  59.  * This resource being per-connection and, in the first place, per-fibril, we
  60.  * don't need to protect it by a mutex.
  61.  */
  62. fibril_local vfs_file_t **files = NULL;
  63.  
  64. /** Initialize the table of open files. */
  65. bool vfs_files_init(void)
  66. {
  67.     if (!files) {
  68.         files = malloc(MAX_OPEN_FILES * sizeof(vfs_file_t *));
  69.         if (!files)
  70.             return false;
  71.         memset(files, 0, MAX_OPEN_FILES * sizeof(vfs_file_t *));
  72.     }
  73.     return true;
  74. }
  75.  
  76. /** Allocate a file descriptor.
  77.  *
  78.  * @return      First available file descriptor or a negative error
  79.  *          code.
  80.  */
  81. int vfs_fd_alloc(void)
  82. {
  83.     if (!vfs_files_init())
  84.         return ENOMEM;
  85.    
  86.     unsigned int i;
  87.     for (i = 0; i < MAX_OPEN_FILES; i++) {
  88.         if (!files[i]) {
  89.             files[i] = (vfs_file_t *) malloc(sizeof(vfs_file_t));
  90.             if (!files[i])
  91.                 return ENOMEM;
  92.            
  93.             memset(files[i], 0, sizeof(vfs_file_t));
  94.             fibril_mutex_initialize(&files[i]->lock);
  95.             vfs_file_addref(files[i]);
  96.             return (int) i;
  97.         }
  98.     }
  99.    
  100.     return EMFILE;
  101. }
  102.  
  103. /** Release file descriptor.
  104.  *
  105.  * @param fd        File descriptor being released.
  106.  *
  107.  * @return      EOK on success or EBADF if fd is an invalid file
  108.  *          descriptor.
  109.  */
  110. int vfs_fd_free(int fd)
  111. {
  112.     if (!vfs_files_init())
  113.         return ENOMEM;
  114.    
  115.     if ((fd < 0) || (fd >= MAX_OPEN_FILES) || (files[fd] == NULL))
  116.         return EBADF;
  117.    
  118.     vfs_file_delref(files[fd]);
  119.     files[fd] = NULL;
  120.    
  121.     return EOK;
  122. }
  123.  
  124. /** Increment reference count of VFS file structure.
  125.  *
  126.  * @param file      File structure that will have reference count
  127.  *          incremented.
  128.  */
  129. void vfs_file_addref(vfs_file_t *file)
  130. {
  131.     /*
  132.      * File structures are per-connection, so no-one, except the current
  133.      * fibril, should have a reference to them. This is the reason we don't
  134.      * do any synchronization here.
  135.      */
  136.     file->refcnt++;
  137. }
  138.  
  139. /** Decrement reference count of VFS file structure.
  140.  *
  141.  * @param file      File structure that will have reference count
  142.  *          decremented.
  143.  */
  144. void vfs_file_delref(vfs_file_t *file)
  145. {
  146.     if (file->refcnt-- == 1) {
  147.         /*
  148.          * Lost the last reference to a file, need to drop our reference
  149.          * to the underlying VFS node.
  150.          */
  151.         vfs_node_delref(file->node);
  152.         free(file);
  153.     }
  154. }
  155.  
  156. /** Find VFS file structure for a given file descriptor.
  157.  *
  158.  * @param fd        File descriptor.
  159.  *
  160.  * @return      VFS file structure corresponding to fd.
  161.  */
  162. vfs_file_t *vfs_file_get(int fd)
  163. {
  164.     if (!vfs_files_init())
  165.         return NULL;
  166.    
  167.     if ((fd >= 0) && (fd < MAX_OPEN_FILES))
  168.         return files[fd];
  169.    
  170.     return NULL;
  171. }
  172.  
  173. /**
  174.  * @}
  175.  */
  176.