WebSVN – HelenOS – Blame – /branches/dd/uspace/srv/vfs/vfs_file.c

Rev	Author	Line No.	Line
4419	trochtova	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>
4537	trochtova	43	#include <fibril.h>
		44	#include <fibril_sync.h>
4419	trochtova	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 futex.
		61	*/
4537	trochtova	62	fibril_local vfs_file_t **files = NULL;
4419	trochtova	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	{
4439	trochtova	83	if (!vfs_files_init())
		84	return ENOMEM;
		85
		86	unsigned int i;
4419	trochtova	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;
4439	trochtova	92
4419	trochtova	93	memset(files[i], 0, sizeof(vfs_file_t));
4537	trochtova	94	fibril_mutex_initialize(&files[i]->lock);
4419	trochtova	95	vfs_file_addref(files[i]);
4439	trochtova	96	return (int) i;
4419	trochtova	97	}
		98	}
4439	trochtova	99
4419	trochtova	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	{
4439	trochtova	112	if (!vfs_files_init())
		113	return ENOMEM;
		114
4420	trochtova	115	if ((fd < 0) \|\| (fd >= MAX_OPEN_FILES) \|\| (files[fd] == NULL))
4419	trochtova	116	return EBADF;
4439	trochtova	117
4419	trochtova	118	vfs_file_delref(files[fd]);
		119	files[fd] = NULL;
4439	trochtova	120
4419	trochtova	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	{
4439	trochtova	164	if (!vfs_files_init())
		165	return NULL;
		166
4420	trochtova	167	if ((fd >= 0) && (fd < MAX_OPEN_FILES))
4419	trochtova	168	return files[fd];
4439	trochtova	169
4419	trochtova	170	return NULL;
		171	}
		172
		173	/**
		174	* @}
4439	trochtova	175	*/

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