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2593 jermar 1
/*
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 * Copyright (c) 2007 Jakub Jermar
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 * All rights reserved.
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 *
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 * Redistribution and use in source and binary forms, with or without
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 * modification, are permitted provided that the following conditions
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 * are met:
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 *
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 * - Redistributions of source code must retain the above copyright
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 *   notice, this list of conditions and the following disclaimer.
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 * - Redistributions in binary form must reproduce the above copyright
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 *   notice, this list of conditions and the following disclaimer in the
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 *   documentation and/or other materials provided with the distribution.
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 * - The name of the author may not be used to endorse or promote products
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 *   derived from this software without specific prior written permission.
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 *
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 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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 */
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/** @addtogroup fs
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 * @{
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 */
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/**
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 * @file    vfs_file.c
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 * @brief   Various operations on files have their home in this file.
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 */
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#include <errno.h>
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#include <stdlib.h>
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#include <string.h>
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#include <assert.h>
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#include <bool.h>
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#include "vfs.h"
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/**
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 * This is a per-connection table of open files.
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 * Our assumption is that each client opens only one connection and therefore
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 * there is one table of open files per task. However, this may not be the case
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 * and the client can open more connections to VFS. In that case, there will be
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 * several tables and several file handle name spaces per task. Besides of this,
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 * the functionality will stay unchanged. So unless the client knows what it is
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 * doing, it should open one connection to VFS only.
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 *
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 * Allocation of the open files table is deferred until the client makes the
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 * first VFS_OPEN operation.
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 *
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 * This resource being per-connection and, in the first place, per-fibril, we
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 * don't need to protect it by a futex.
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 */
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__thread vfs_file_t **files = NULL;
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/** Initialize the table of open files. */
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bool vfs_files_init(void)
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{
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    if (!files) {
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        files = malloc(MAX_OPEN_FILES * sizeof(vfs_file_t *));
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        if (!files)
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            return false;
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        memset(files, 0, MAX_OPEN_FILES * sizeof(vfs_file_t *));
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    }
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    return true;
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}
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/** Allocate a file descriptor.
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 *
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 * @return      First available file descriptor or a negative error
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 *          code.
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 */
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int vfs_fd_alloc(void)
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{
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    int i;
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    for (i = 0; i < MAX_OPEN_FILES; i++) {
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        if (!files[i]) {
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            files[i] = (vfs_file_t *) malloc(sizeof(vfs_file_t));
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            if (!files[i])
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                return ENOMEM;
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            memset(files[i], 0, sizeof(vfs_file_t));
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            futex_initialize(&files[i]->lock, 1);
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            vfs_file_addref(files[i]);
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            return i;
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        }
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    }
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    return EMFILE;
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}
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/** Release file descriptor.
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 *
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 * @param fd        File descriptor being released.
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 */
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void vfs_fd_free(int fd)
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{
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    assert(fd < MAX_OPEN_FILES);
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    assert(files[fd] != NULL);
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    vfs_file_delref(files[fd]);
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    files[fd] = NULL;
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}
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/** Increment reference count of VFS file structure.
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 *
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 * @param file      File structure that will have reference count
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 *          incremented.
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 */
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void vfs_file_addref(vfs_file_t *file)
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{
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    /*
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     * File structures are per-connection, so no-one, except the current
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     * fibril, should have a reference to them. This is the reason we don't
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     * do any synchronization here.
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     */
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    file->refcnt++;
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}
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/** Decrement reference count of VFS file structure.
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 *
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 * @param file      File structure that will have reference count
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 *          decremented.
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 */
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void vfs_file_delref(vfs_file_t *file)
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{
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    if (file->refcnt-- == 1) {
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        /*
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         * Lost the last reference to a file, need to drop our reference
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         * to the underlying VFS node.
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         */
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        vfs_node_delref(file->node);
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        free(file);
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    }
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}
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/** Find VFS file structure for a given file descriptor.
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 *
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 * @param fd        File descriptor.
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 *
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 * @return      VFS file structure corresponding to fd.
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 */
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vfs_file_t *vfs_file_get(int fd)
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{
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    if (fd < MAX_OPEN_FILES)
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        return files[fd];
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    return NULL;
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}
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/**
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 * @}
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 */