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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

/** Futex protecting the list of cached free FAT nodes. */

static futex_t ffn_futex = FUTEX_INITIALIZER;

/** List of cached free FAT nodes. */

static LIST_INITIALIZE(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 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_RES0   0x0000

#define FAT_CLST_RES1   0x0001  /* internally used to mark root directory */

#define FAT_CLST_FIRST  0x0002

#define FAT_CLST_BAD    0xfff7

#define FAT_CLST_LAST1  0xfff8

#define FAT_CLST_LAST8  0xffff

#define fat_block_get(np, off) \

    _fat_block_get((np)->idx->dev_handle, (np)->firstc, (off))

static block_t *

_fat_block_get(dev_handle_t dev_handle, fat_cluster_t firstc, 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;

    fat_cluster_t clst = firstc;

    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 (firstc == FAT_CLST_RES1) {

        /* 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 = (clst * sizeof(fat_cluster_t)) / bps;

        fidx = clst % (bps / sizeof(fat_cluster_t));

        /* read FAT1 */

        b = block_get(dev_handle, rscnt + fsec);

        clst = uint16_t_le2host(((fat_cluster_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->idx = NULL;

    node->type = 0;

    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_node_sync(fat_node_t *node)

{

    /* TODO */

}

/** Internal version of fat_node_get().

 *

 * @param idxp      Locked index structure.

 */

static void *fat_node_get_core(fat_idx_t *idxp)

{

    block_t *b;

    fat_dentry_t *d;

    fat_node_t *nodep;

    unsigned bps;

    unsigned dps;

    if (idxp->nodep) {

        /*

         * We are lucky.

         * The node is already instantiated in memory.

         */

        futex_down(&idxp->nodep->lock);

        if (!idxp->nodep->refcnt++)

            list_remove(&nodep->ffn_link);

        futex_up(&idxp->nodep->lock);

        return idxp->nodep;

    }

    /*

     * We must instantiate the node from the file system.

     */

    assert(idxp->pfc);

    futex_down(&ffn_futex);

    if (!list_empty(&ffn_head)) {

        /* Try to use a cached free node structure. */

        fat_idx_t *idxp_tmp;

        nodep = list_get_instance(ffn_head.next, fat_node_t, ffn_link);

        if (futex_trydown(&nodep->lock) == ESYNCH_WOULD_BLOCK)

            goto skip_cache;

        idxp_tmp = nodep->idx;

        if (futex_trydown(&idxp_tmp->lock) == ESYNCH_WOULD_BLOCK) {

            futex_up(&nodep->lock);

            goto skip_cache;

        }

        list_remove(&nodep->ffn_link);

        futex_up(&ffn_futex);

        if (nodep->dirty)

            fat_node_sync(nodep);

        idxp_tmp->nodep = NULL;

        futex_up(&nodep->lock);

        futex_up(&idxp_tmp->lock);

    } else {

skip_cache:

        /* Try to allocate a new node structure. */

        futex_up(&ffn_futex);

        nodep = (fat_node_t *)malloc(sizeof(fat_node_t));

        if (!nodep)

            return NULL;

    }

    fat_node_initialize(nodep);

    bps = fat_bps_get(idxp->dev_handle);

    dps = bps / sizeof(fat_dentry_t);

    /* Read the block that contains the dentry of interest. */

    b = _fat_block_get(idxp->dev_handle, idxp->pfc,

        (idxp->pdi * sizeof(fat_dentry_t)) / bps);

    assert(b);

    d = ((fat_dentry_t *)b->data) + (idxp->pdi % dps);

    if (d->attr & FAT_ATTR_SUBDIR) {

        /*

         * The only directory which does not have this bit set is the

         * root directory itself. The root directory node is handled

         * and initialized elsewhere.

         */

        nodep->type = FAT_DIRECTORY;

    } else {

        nodep->type = FAT_FILE;

    }

    nodep->firstc = uint16_t_le2host(d->firstc);

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

    nodep->lnkcnt = 1;

    nodep->refcnt = 1;

    block_put(b);

    /* Link the idx structure with the node structure. */

    nodep->idx = idxp;

    idxp->nodep = nodep;

    return nodep;

}

/** Instantiate a FAT in-core node. */

static void *fat_node_get(dev_handle_t dev_handle, fs_index_t index)

{

    void *node;

    fat_idx_t *idxp;

    idxp = fat_idx_get_by_index(dev_handle, index);

    if (!idxp)

        return NULL;

    /* idxp->lock held */

    node = fat_node_get_core(idxp);

    futex_up(&idxp->lock);

    return node;

}

static void fat_node_put(void *node)

{

    fat_node_t *nodep = (fat_node_t *)node;

    futex_down(&nodep->lock);

    if (!--nodep->refcnt) {

        futex_down(&ffn_futex);

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

        futex_up(&ffn_futex);

    }

    futex_up(&nodep->lock);

}

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;

    futex_down(&parentp->idx->lock);

    bps = fat_bps_get(parentp->idx->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, 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);

                futex_up(&parentp->idx->lock);

                return NULL;

            default:

            case FAT_DENTRY_VALID:

                dentry_name_canonify(d, name);

                break;

            }

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

                /* hit */

                void *node;

                /*

                 * Assume tree hierarchy for locking.  We

                 * already have the parent and now we are going

                 * to lock the child.  Never lock in the oposite

                 * order.

                 */

                fat_idx_t *idx = fat_idx_get_by_pos(

                    parentp->idx->dev_handle, parentp->firstc,

                    i * dps + j);

                futex_up(&parentp->idx->lock);

                if (!idx) {

                    /*

                     * Can happen if memory is low or if we

                     * run out of 32-bit indices.

                     */

                    block_put(b);

                    return NULL;

                }

                node = fat_node_get_core(idx);

                futex_up(&idx->lock);

                block_put(b);

                return node;

            }

        }

        block_put(b);

    }

    futex_up(&parentp->idx->lock);

    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->idx->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;

    futex_down(&nodep->idx->lock);

    bps = fat_bps_get(nodep->idx->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, 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);

                futex_up(&nodep->idx->lock);

                return false;

            default:

            case FAT_DENTRY_VALID:

                block_put(b);

                futex_up(&nodep->idx->lock);

                return true;

            }

            block_put(b);

            futex_up(&nodep->idx->lock);

            return true;

        }

        block_put(b);

    }

    futex_up(&nodep->idx->lock);

    return false;

}

static void *fat_root_get(dev_handle_t dev_handle)

{

    return NULL;    /* TODO */

}

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);

}

/**

 * @}

 */