source: mainline/uspace/srv/vfs/vfs_file.c@ 667a4f8

/*
 * Copyright (c) 2007 Jakub Jermar
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/** @addtogroup fs
 * @{
 */ 

/**
 * @file        vfs_file.c
 * @brief       Various operations on files have their home in this file.
 */

#include <errno.h>
#include <stdlib.h>
#include <str.h>
#include <assert.h>
#include <bool.h>
#include <fibril.h>
#include <fibril_synch.h>
#include "vfs.h"

#define VFS_DATA        ((vfs_client_data_t *) async_client_data_get())
#define FILES           (VFS_DATA->files)

typedef struct {
        fibril_mutex_t lock;
        vfs_file_t **files;
} vfs_client_data_t;

/** Initialize the table of open files. */
static bool vfs_files_init(void)
{
        fibril_mutex_lock(&VFS_DATA->lock);
        if (!FILES) {
                FILES = malloc(MAX_OPEN_FILES * sizeof(vfs_file_t *));
                if (!FILES) {
                        fibril_mutex_unlock(&VFS_DATA->lock);
                        return false;
                }
                memset(FILES, 0, MAX_OPEN_FILES * sizeof(vfs_file_t *));
        }
        fibril_mutex_unlock(&VFS_DATA->lock);
        return true;
}

/** Cleanup the table of open files. */
static void vfs_files_done(void)
{
        int i;

        if (!FILES)
                return;

        for (i = 0; i < MAX_OPEN_FILES; i++) {
                if (FILES[i]) {
                        (void) vfs_close_internal(FILES[i]);
                        (void) vfs_fd_free(i);
                }
        }
        
        free(FILES);
}

void *vfs_client_data_create(void)
{
        vfs_client_data_t *vfs_data;

        vfs_data = malloc(sizeof(vfs_client_data_t));
        if (vfs_data) {
                fibril_mutex_initialize(&vfs_data->lock);
                vfs_data->files = NULL;
        }
        
        return vfs_data;
}

void vfs_client_data_destroy(void *data)
{
        vfs_client_data_t *vfs_data = (vfs_client_data_t *) data;

        vfs_files_done();
        free(vfs_data);
}

/** Increment reference count of VFS file structure.
 *
 * @param file          File structure that will have reference count
 *                      incremented.
 */
static void vfs_file_addref(vfs_file_t *file)
{
        assert(fibril_mutex_is_locked(&VFS_DATA->lock));

        file->refcnt++;
}

/** Decrement reference count of VFS file structure.
 *
 * @param file          File structure that will have reference count
 *                      decremented.
 */
static void vfs_file_delref(vfs_file_t *file)
{
        assert(fibril_mutex_is_locked(&VFS_DATA->lock));

        if (file->refcnt-- == 1) {
                /*
                 * Lost the last reference to a file, need to drop our reference
                 * to the underlying VFS node.
                 */
                vfs_node_delref(file->node);
                free(file);
        }
}


/** Allocate a file descriptor.
 *
 * @param desc If true, look for an available file descriptor
 *             in a descending order.
 *
 * @return First available file descriptor or a negative error
 *         code.
 */
int vfs_fd_alloc(bool desc)
{
        if (!vfs_files_init())
                return ENOMEM;
        
        unsigned int i;
        if (desc)
                i = MAX_OPEN_FILES - 1;
        else
                i = 0;
        
        fibril_mutex_lock(&VFS_DATA->lock);
        while (true) {
                if (!FILES[i]) {
                        FILES[i] = (vfs_file_t *) malloc(sizeof(vfs_file_t));
                        if (!FILES[i]) {
                                fibril_mutex_unlock(&VFS_DATA->lock);
                                return ENOMEM;
                        }
                        
                        memset(FILES[i], 0, sizeof(vfs_file_t));
                        fibril_mutex_initialize(&FILES[i]->lock);
                        vfs_file_addref(FILES[i]);
                        fibril_mutex_unlock(&VFS_DATA->lock);
                        return (int) i;
                }
                
                if (desc) {
                        if (i == 0)
                                break;
                        
                        i--;
                } else {
                        if (i == MAX_OPEN_FILES - 1)
                                break;
                        
                        i++;
                }
        }
        fibril_mutex_unlock(&VFS_DATA->lock);
        
        return EMFILE;
}

/** Release file descriptor.
 *
 * @param fd            File descriptor being released.
 *
 * @return              EOK on success or EBADF if fd is an invalid file
 *                      descriptor.
 */
int vfs_fd_free(int fd)
{
        if (!vfs_files_init())
                return ENOMEM;

        fibril_mutex_lock(&VFS_DATA->lock);     
        if ((fd < 0) || (fd >= MAX_OPEN_FILES) || (FILES[fd] == NULL)) {
                fibril_mutex_unlock(&VFS_DATA->lock);
                return EBADF;
        }
        
        vfs_file_delref(FILES[fd]);
        FILES[fd] = NULL;
        fibril_mutex_unlock(&VFS_DATA->lock);
        
        return EOK;
}

/** Assign a file to a file descriptor.
 *
 * @param file File to assign.
 * @param fd   File descriptor to assign to.
 *
 * @return EOK on success or EINVAL if fd is an invalid or already
 *         used file descriptor.
 *
 */
int vfs_fd_assign(vfs_file_t *file, int fd)
{
        if (!vfs_files_init())
                return ENOMEM;

        fibril_mutex_lock(&VFS_DATA->lock);     
        if ((fd < 0) || (fd >= MAX_OPEN_FILES) || (FILES[fd] != NULL)) {
                fibril_mutex_unlock(&VFS_DATA->lock);
                return EINVAL;
        }
        
        FILES[fd] = file;
        vfs_file_addref(FILES[fd]);
        fibril_mutex_unlock(&VFS_DATA->lock);
        
        return EOK;
}

/** Find VFS file structure for a given file descriptor.
 *
 * @param fd            File descriptor.
 *
 * @return              VFS file structure corresponding to fd.
 */
vfs_file_t *vfs_file_get(int fd)
{
        if (!vfs_files_init())
                return NULL;
        
        fibril_mutex_lock(&VFS_DATA->lock);
        if ((fd >= 0) && (fd < MAX_OPEN_FILES)) {
                vfs_file_t *file = FILES[fd];
                vfs_file_addref(file);
                fibril_mutex_unlock(&VFS_DATA->lock);
                return file;
        }
        fibril_mutex_unlock(&VFS_DATA->lock);
        
        return NULL;
}

/** Stop using a file structure.
 *
 * @param file          VFS file structure.
 */
void vfs_file_put(vfs_file_t *file)
{
        fibril_mutex_lock(&VFS_DATA->lock);
        vfs_file_delref(file);
        fibril_mutex_unlock(&VFS_DATA->lock);
}

/**
 * @}
 */