source: mainline/uspace/srv/fs/fat/fat_ops.c@ 45f244b

/*
 * 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);
}

/**
 * @}
 */