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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 void block_put(block_t *block)

{

    /* TODO */

}

#define FAT_BS(b)       ((fat_bs_t *)((b)->data))

#define FAT_CLST_FIRST  0x0002

#define FAT_CLST_BAD    0xfff7

#define FAT_CLST_LAST1  0xfff8

#define FAT_CLST_LAST8  0xffff

/** Convert cluster number to an index within a FAT.

 *

 * Format Identifier and cluster numbering is considered.

 */

#define C2FAT_IDX(c)    (1 + (c) - FAT_CLST_FIRST)

static block_t *fat_block_get(dev_handle_t dev_handle, fs_index_t index,

    off_t offset)

{

    block_t *bb;

    block_t *b;

    unsigned bps;

    unsigned spc;

    unsigned rscnt;     /* block address of the first FAT */

    unsigned fatcnt;

    unsigned rde;

    unsigned rds;       /* root directory size */

    unsigned sf;

    unsigned ssa;       /* size of the system area */

    unsigned clusters;

    unsigned clst = index;

    unsigned i;

    bb = block_get(dev_handle, BS_BLOCK);

    bps = uint16_t_le2host(FAT_BS(bb)->bps);

    spc = FAT_BS(bb)->spc;

    rscnt = uint16_t_le2host(FAT_BS(bb)->rscnt);

    fatcnt = FAT_BS(bb)->fatcnt;

    rde = uint16_t_le2host(FAT_BS(bb)->root_ent_max);

    sf = uint16_t_le2host(FAT_BS(bb)->sec_per_fat);

    block_put(bb);

    rds = (sizeof(fat_dentry_t) * rde) / bps;

    rds += ((sizeof(fat_dentry_t) * rde) % bps != 0);

    ssa = rscnt + fatcnt * sf + rds;

    if (!index) {

        /* root directory special case */

        assert(offset < rds);

        b = block_get(dev_handle, rscnt + fatcnt * sf + offset);

        return b;

    }

    clusters = offset / spc;

    for (i = 0; i < clusters; i++) {

        unsigned fsec;  /* sector offset relative to FAT1 */

        unsigned fidx;  /* FAT1 entry index */

        assert(clst >= FAT_CLST_FIRST && clst < FAT_CLST_BAD);

        fsec = (C2FAT_IDX(clst) * sizeof(uint16_t)) / bps;

        fidx = C2FAT_IDX(clst) % (bps / sizeof(uint16_t));

        /* read FAT1 */

        b = block_get(dev_handle, rscnt + fsec);

        clst = uint16_t_le2host(((uint16_t *)b->data)[fidx]);

        assert(clst != FAT_CLST_BAD);

        assert(clst < FAT_CLST_LAST1);

        block_put(b);

    }

    b = block_get(dev_handle, ssa + (clst - FAT_CLST_FIRST) * spc +

        offset % spc);

    return b;

}

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(bb)->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);

}

/**

 * @}

 */