source: mainline/uspace/srv/fs/fat/fat_ops.c@ 79dbc3e

/*
 * 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>

#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(fat_node_t *node, off_t offset) {
        return NULL;    /* TODO */
}

static void block_put(block_t *block)
{
        /* TODO */
}

static void *fat_node_get(dev_handle_t dev_handle, fs_index_t index)
{
        return NULL;    /* TODO */
}

#define BS_BLOCK        0

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 dps;           /* dentries per sector */
        unsigned blocks;
        fat_dentry_t *d;
        block_t *bb;
        block_t *b;
        fat_bs_t *bs;

        bb = block_get(parentp->dev_handle, BS_BLOCK);
        if (!bb)
                return NULL;
        bs = (fat_bs_t *)bb->data;
        dps = bs->bps / sizeof(fat_dentry_t);
        blocks = parentp->size / bs->bps + (parentp->size % bs->bps != 0);
        block_put(bb);
        for (i = 0; i < blocks; i++) {
                unsigned dentries;
                
                b = fat_block_get(parentp, i);
                if (!b) 
                        return NULL;

                dentries = (i == blocks - 1) ?
                    parentp->size % sizeof(fat_dentry_t) :
                    dps;
                for (j = 0; j < dentries; j++) { 
                        d = ((fat_dentry_t *)b->data) + j;
                        if (d->attr & FAT_ATTR_VOLLABEL) {
                                /* volume label entry */
                                continue;
                        }
                        if (d->name[0] == FAT_DENTRY_ERASED) {
                                /* not-currently-used entry */
                                continue;
                        }
                        if (d->name[0] == FAT_DENTRY_UNUSED) {
                                /* never used entry */
                                block_put(b);
                                return NULL;
                        }
                        if (d->name[0] == FAT_DENTRY_DOT) {
                                /*
                                 * Most likely '.' or '..'.
                                 * It cannot occur in a regular file name.
                                 */
                                continue;
                        }
                
                        dentry_name_canonify(d, name);
                        if (strcmp(name, component) == 0) {
                                /* hit */
                                void *node = fat_node_get(parentp->dev_handle,
                                    (fs_index_t)uint16_t_le2host(d->firstc));
                                block_put(b);
                                return node;
                        }
                }
                block_put(b);
        }

        return NULL;
}

/** libfs operations */
libfs_ops_t fat_libfs_ops = {
        .match = fat_match,
        .node_get = fat_node_get,
        .create = NULL,
        .destroy = NULL,
        .link = NULL,
        .unlink = NULL,
        .index_get = NULL,
        .size_get = NULL,
        .lnkcnt_get = NULL,
        .has_children = NULL,
        .root_get = NULL,
        .plb_get_char = NULL,
        .is_directory = NULL,
        .is_file = NULL
};

void fat_lookup(ipc_callid_t rid, ipc_call_t *request)
{
        libfs_lookup(&fat_libfs_ops, fat_reg.fs_handle, rid, request);
}

/**
 * @}
 */