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/*

 * Copyright (c) 2008 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	fat_ops.c

 * @brief	Implementation of VFS operations for the FAT file system server.

 */

#include "fat.h"

#include "../../vfs/vfs.h"

#include <libfs.h>

#include <ipc/ipc.h>

#include <async.h>

#include <errno.h>

#include <string.h>

#include <byteorder.h>

#include <libadt/hash_table.h>

#include <libadt/list.h>

#include <assert.h>

#include <futex.h>

#define BS_BLOCK		0

#define FIN_KEY_DEV_HANDLE	0

#define FIN_KEY_INDEX		1

/** Futex protecting both fin_hash and ffn_head. */

futex_t fin_futex = FUTEX_INITIALIZER;

/** Hash table of FAT in-core nodes. */

hash_table_t fin_hash;

/** List of free FAT in-core nodes. */

link_t ffn_head;

#define FAT_NAME_LEN		8

#define FAT_EXT_LEN		3

#define FAT_PAD			' ' 

#define FAT_DENTRY_UNUSED	0x00

#define FAT_DENTRY_E5_ESC	0x05

#define FAT_DENTRY_DOT		0x2e

#define FAT_DENTRY_ERASED	0xe5

static void dentry_name_canonify(fat_dentry_t *d, char *buf)

{

	int i;

	for (i = 0; i < FAT_NAME_LEN; i++) {

		if (d->name[i] == FAT_PAD) {

			buf++;

			break;

		}

		if (d->name[i] == FAT_DENTRY_E5_ESC)

			*buf++ = 0xe5;

		else

			*buf++ = d->name[i];

	}

	if (d->ext[0] != FAT_PAD)

		*buf++ = '.';

	for (i = 0; i < FAT_EXT_LEN; i++) {

		if (d->ext[i] == FAT_PAD) {

			*buf = '\0';

			return;

		}

		if (d->ext[i] == FAT_DENTRY_E5_ESC)

			*buf++ = 0xe5;

		else

			*buf++ = d->ext[i];

	}

}

/* TODO and also move somewhere else */

typedef struct {

	void *data;

} block_t;

static block_t *block_get(dev_handle_t dev_handle, off_t offset)

{

	return NULL;	/* TODO */

}

static block_t *fat_block_get(dev_handle_t dev_handle, fs_index_t index,

    off_t offset) {

	return NULL;	/* TODO */

}

static void block_put(block_t *block)

{

	/* TODO */

}

static void fat_node_initialize(fat_node_t *node)

{

	futex_initialize(&node->lock, 1);

	node->type = 0;

	node->index = 0;

	node->pindex = 0;

	node->dev_handle = 0;

	link_initialize(&node->fin_link);

	link_initialize(&node->ffn_link);

	node->size = 0;

	node->lnkcnt = 0;

	node->refcnt = 0;

	node->dirty = false;

}

static uint16_t fat_bps_get(dev_handle_t dev_handle)

{

	block_t *bb;

	uint16_t bps;

	bb = block_get(dev_handle, BS_BLOCK);

	assert(bb != NULL);

	bps = uint16_t_le2host(((fat_bs_t *)bb->data)->bps);

	block_put(bb);

	return bps;

}

typedef enum {

	FAT_DENTRY_SKIP,

	FAT_DENTRY_LAST,

	FAT_DENTRY_VALID

} fat_dentry_clsf_t;

static fat_dentry_clsf_t fat_classify_dentry(fat_dentry_t *d)

{

	if (d->attr & FAT_ATTR_VOLLABEL) {

		/* volume label entry */

		return FAT_DENTRY_SKIP;

	}

	if (d->name[0] == FAT_DENTRY_ERASED) {

		/* not-currently-used entry */

		return FAT_DENTRY_SKIP;

	}

	if (d->name[0] == FAT_DENTRY_UNUSED) {

		/* never used entry */

		return FAT_DENTRY_LAST;

	}

	if (d->name[0] == FAT_DENTRY_DOT) {

		/*

		 * Most likely '.' or '..'.

		 * It cannot occur in a regular file name.

		 */

		return FAT_DENTRY_SKIP;

	}

	return FAT_DENTRY_VALID;

}

static void fat_sync_node(fat_node_t *node)

{

	/* TODO */

}

/** Instantiate a FAT in-core node.

 *

 * FAT stores the info necessary for instantiation of a node in the parent of

 * that node.  This design necessitated the addition of the parent node index

 * parameter to this otherwise generic libfs API.

 */

static void *

fat_node_get(dev_handle_t dev_handle, fs_index_t index, fs_index_t pindex)

{

	link_t *lnk;

	fat_node_t *node = NULL;

	block_t *b;

	unsigned bps;

	unsigned dps;

	fat_dentry_t *d;

	unsigned i, j;

	unsigned long key[] = {

		[FIN_KEY_DEV_HANDLE] = dev_handle,

		[FIN_KEY_INDEX] = index

	};

	futex_down(&fin_futex);

	lnk = hash_table_find(&fin_hash, key);

	if (lnk) {

		/*

		 * The in-core node was found in the hash table.

		 */

		node = hash_table_get_instance(lnk, fat_node_t, fin_link);

		if (!node->refcnt++)

			list_remove(&node->ffn_link);

		futex_up(&fin_futex);

		/* Make sure that the node is fully instantiated. */

		futex_down(&node->lock);

		futex_up(&node->lock);

		return (void *) node;	

	}

	bps = fat_bps_get(dev_handle);

	dps = bps / sizeof(fat_dentry_t);

	if (!list_empty(&ffn_head)) {

		/*

		 * We are going to reuse a node from the free list.

		 */

		lnk = ffn_head.next; 

		list_remove(lnk);

		node = list_get_instance(lnk, fat_node_t, ffn_link);

		assert(!node->refcnt);

		if (node->dirty)

			fat_sync_node(node);

		key[FIN_KEY_DEV_HANDLE] = node->dev_handle;

		key[FIN_KEY_INDEX] = node->index;

		hash_table_remove(&fin_hash, key, sizeof(key)/sizeof(*key));

	} else {

		/*

		 * We need to allocate a new node.

		 */

		node = malloc(sizeof(fat_node_t));

		if (!node)

			return NULL;

	}

	fat_node_initialize(node);

	node->refcnt++;

	node->lnkcnt++;

	node->dev_handle = dev_handle;

	node->index = index;

	node->pindex = pindex;

	key[FIN_KEY_DEV_HANDLE] = node->dev_handle;

	key[FIN_KEY_INDEX] = node->index;

	hash_table_insert(&fin_hash, key, &node->fin_link);

	/*

	 * We have already put the node back to fin_hash.

	 * The node is not yet fully instantiated so we lock it prior to

	 * unlocking fin_hash.

	 */

	futex_down(&node->lock);

	futex_up(&fin_futex);

	/*

	 * Because of the design of the FAT file system, we have no clue about

	 * how big (i.e. how many directory entries it contains) is the parent

	 * of the node we are trying to instantiate.  However, we know that it

	 * must contain a directory entry for our node of interest.  We simply

	 * scan the parent until we find it.

	 */

	for (i = 0; ; i++) {

		b = fat_block_get(node->dev_handle, node->pindex, i);

		for (j = 0; j < dps; j++) {

			d = ((fat_dentry_t *)b->data) + j;

			if (d->firstc == node->index)

				goto found;

		}

		block_put(b);

	}

found:

	if (!(d->attr & (FAT_ATTR_SUBDIR | FAT_ATTR_VOLLABEL)))

		node->type = FAT_FILE;

	if ((d->attr & FAT_ATTR_SUBDIR) || !index)

		node->type = FAT_DIRECTORY;

	assert((node->type == FAT_FILE) || (node->type == FAT_DIRECTORY));

	node->size = uint32_t_le2host(d->size);

	block_put(b);

	futex_up(&node->lock);

	return node;

}

static void fat_node_put(void *node)

{

	fat_node_t *nodep = (fat_node_t *)node;

	futex_down(&fin_futex);

	if (!--nodep->refcnt)

		list_append(&nodep->ffn_link, &ffn_head);

	futex_up(&fin_futex);

}

static void *fat_create(int flags)

{

	return NULL;	/* not supported at the moment */

}

static int fat_destroy(void *node)

{

	return ENOTSUP;	/* not supported at the moment */

}

static bool fat_link(void *prnt, void *chld, const char *name)

{

	return false;	/* not supported at the moment */

}

static int fat_unlink(void *prnt, void *chld)

{

	return ENOTSUP;	/* not supported at the moment */

}

static void *fat_match(void *prnt, const char *component)

{

	fat_node_t *parentp = (fat_node_t *)prnt;

	char name[FAT_NAME_LEN + 1 + FAT_EXT_LEN + 1];

	unsigned i, j;

	unsigned bps;		/* bytes per sector */

	unsigned dps;		/* dentries per sector */

	unsigned blocks;

	fat_dentry_t *d;

	block_t *b;

	bps = fat_bps_get(parentp->dev_handle);

	dps = bps / sizeof(fat_dentry_t);

	blocks = parentp->size / bps + (parentp->size % bps != 0);

	for (i = 0; i < blocks; i++) {

		unsigned dentries;

		b = fat_block_get(parentp->dev_handle, parentp->index, i);

		dentries = (i == blocks - 1) ?

		    parentp->size % sizeof(fat_dentry_t) :

		    dps;

		for (j = 0; j < dentries; j++) { 

			d = ((fat_dentry_t *)b->data) + j;

			switch (fat_classify_dentry(d)) {

			case FAT_DENTRY_SKIP:

				continue;

			case FAT_DENTRY_LAST:

				block_put(b);

				return NULL;

			default:

			case FAT_DENTRY_VALID:

				dentry_name_canonify(d, name);

				break;

			}

			if (strcmp(name, component) == 0) {

				/* hit */

				void *node = fat_node_get(parentp->dev_handle,

				    (fs_index_t)uint16_t_le2host(d->firstc),

				    parentp->index);

				block_put(b);

				return node;

			}

		}

		block_put(b);

	}

	return NULL;

}

static fs_index_t fat_index_get(void *node)

{

	fat_node_t *fnodep = (fat_node_t *)node;

	if (!fnodep)

		return 0;

	return fnodep->index;

}

static size_t fat_size_get(void *node)

{

	return ((fat_node_t *)node)->size;

}

static unsigned fat_lnkcnt_get(void *node)

{

	return ((fat_node_t *)node)->lnkcnt;

}

static bool fat_has_children(void *node)

{

	fat_node_t *nodep = (fat_node_t *)node;

	unsigned bps;

	unsigned dps;

	unsigned blocks;

	block_t *b;

	unsigned i, j;

	if (nodep->type != FAT_DIRECTORY)

		return false;

	bps = fat_bps_get(nodep->dev_handle);

	dps = bps / sizeof(fat_dentry_t);

	blocks = nodep->size / bps + (nodep->size % bps != 0);

	for (i = 0; i < blocks; i++) {

		unsigned dentries;

		fat_dentry_t *d;

		b = fat_block_get(nodep->dev_handle, nodep->index, i);

		dentries = (i == blocks - 1) ?

		    nodep->size % sizeof(fat_dentry_t) :

		    dps;

		for (j = 0; j < dentries; j++) {

			d = ((fat_dentry_t *)b->data) + j;

			switch (fat_classify_dentry(d)) {

			case FAT_DENTRY_SKIP:

				continue;

			case FAT_DENTRY_LAST:

				block_put(b);

				return false;

			default:

			case FAT_DENTRY_VALID:

				block_put(b);

				return true;

			}

			block_put(b);

			return true;

		}

		block_put(b);

	}

	return false;

}

static void *fat_root_get(dev_handle_t dev_handle)

{

	return fat_node_get(dev_handle, 0, 0);	

}

static char fat_plb_get_char(unsigned pos)

{

	return fat_reg.plb_ro[pos % PLB_SIZE];

}

static bool fat_is_directory(void *node)

{

	return ((fat_node_t *)node)->type == FAT_DIRECTORY;

}

static bool fat_is_file(void *node)

{

	return ((fat_node_t *)node)->type == FAT_FILE;

}

/** libfs operations */

libfs_ops_t fat_libfs_ops = {

	.match = fat_match,

	.node_get = fat_node_get,

	.node_put = fat_node_put,

	.create = fat_create,

	.destroy = fat_destroy,

	.link = fat_link,

	.unlink = fat_unlink,

	.index_get = fat_index_get,

	.size_get = fat_size_get,

	.lnkcnt_get = fat_lnkcnt_get,

	.has_children = fat_has_children,

	.root_get = fat_root_get,

	.plb_get_char =	fat_plb_get_char,

	.is_directory = fat_is_directory,

	.is_file = fat_is_file

};

void fat_lookup(ipc_callid_t rid, ipc_call_t *request)

{

	libfs_lookup(&fat_libfs_ops, fat_reg.fs_handle, rid, request);

}

/**

 * @}

 */