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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>

#define BS_BLOCK        0

#define FIN_KEY_DEV_HANDLE  0
#define FIN_KEY_INDEX       1

/** 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)
{
    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;
}

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
    };

    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);
        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;

    /*
     * 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);
        if (!b) {
            node->refcnt--;
            list_append(&node->ffn_link, &ffn_head);
            return NULL;
        }
        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);
    
    key[FIN_KEY_DEV_HANDLE] = node->dev_handle;
    key[FIN_KEY_INDEX] = node->index;
    hash_table_insert(&fin_hash, key, &node->fin_link);

    return node;
}

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);
        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),
                    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 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,
    .create = NULL,
    .destroy = NULL,
    .link = NULL,
    .unlink = NULL,
    .index_get = fat_index_get,
    .size_get = fat_size_get,
    .lnkcnt_get = fat_lnkcnt_get,
    .has_children = NULL,
    .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);
}

/**
 * @}
 */