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

Rev	Author	Line No.	Line
2593	jermar	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));
2683	jermar	89	futex_initialize(&files[i]->lock, 1);
2593	jermar	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.
3215	jermar	100	*
		101	* @return EOK on success or EBADF if fd is an invalid file
		102	* descriptor.
2593	jermar	103	*/
3215	jermar	104	int vfs_fd_free(int fd)
2593	jermar	105	{
3215	jermar	106	if ((fd >= MAX_OPEN_FILES) \|\| (files[fd] == NULL))
		107	return EBADF;
2593	jermar	108	vfs_file_delref(files[fd]);
		109	files[fd] = NULL;
3215	jermar	110	return EOK;
2593	jermar	111	}
		112
		113	/** Increment reference count of VFS file structure.
		114	*
		115	* @param file File structure that will have reference count
		116	* incremented.
		117	*/
		118	void vfs_file_addref(vfs_file_t *file)
		119	{
		120	/*
		121	* File structures are per-connection, so no-one, except the current
		122	* fibril, should have a reference to them. This is the reason we don't
		123	* do any synchronization here.
		124	*/
		125	file->refcnt++;
		126	}
		127
		128	/** Decrement reference count of VFS file structure.
		129	*
		130	* @param file File structure that will have reference count
		131	* decremented.
		132	*/
		133	void vfs_file_delref(vfs_file_t *file)
		134	{
		135	if (file->refcnt-- == 1) {
		136	/*
2731	jermar	137	* Lost the last reference to a file, need to drop our reference
2593	jermar	138	* to the underlying VFS node.
		139	*/
		140	vfs_node_delref(file->node);
		141	free(file);
		142	}
		143	}
		144
		145	/** Find VFS file structure for a given file descriptor.
		146	*
		147	* @param fd File descriptor.
		148	*
		149	* @return VFS file structure corresponding to fd.
		150	*/
		151	vfs_file_t *vfs_file_get(int fd)
		152	{
2624	jermar	153	if (fd < MAX_OPEN_FILES)
		154	return files[fd];
		155	return NULL;
2593	jermar	156	}
		157
		158	/**
		159	* @}
		160	*/

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