source: mainline/uspace/srv/fs/cdfs/cdfs_ops.c@ b81ae12

/*
 * Copyright (c) 2024 Jiri Svoboda
 * Copyright (c) 2011 Martin Decky
 * 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 cdfs
 * @{
 */

/**
 * @file cdfs_ops.c
 * @brief Implementation of VFS operations for the cdfs file system
 *        server.
 */

#include "cdfs_ops.h"
#include <stdbool.h>
#include <adt/list.h>
#include <adt/hash_table.h>
#include <adt/hash.h>
#include <mem.h>
#include <loc.h>
#include <libfs.h>
#include <errno.h>
#include <block.h>
#include <scsi/mmc.h>
#include <stdlib.h>
#include <str.h>
#include <byteorder.h>
#include <macros.h>
#include <unaligned.h>

#include "cdfs.h"
#include "cdfs_endian.h"

/** Standard CD-ROM block size */
#define BLOCK_SIZE  2048

#define NODE_CACHE_SIZE 200

/** All root nodes have index 0 */
#define CDFS_SOME_ROOT  0

#define CDFS_NODE(node)  ((node) ? (cdfs_node_t *)(node)->data : NULL)
#define FS_NODE(node)    ((node) ? (node)->fs_node : NULL)

#define CDFS_STANDARD_IDENT  "CD001"

enum {
        CDFS_NAME_CURDIR = '\x00',
        CDFS_NAME_PARENTDIR = '\x01'
};

typedef enum {
        VOL_DESC_BOOT = 0,
        VOL_DESC_PRIMARY = 1,
        VOL_DESC_SUPPLEMENTARY = 2,
        VOL_DESC_VOL_PARTITION = 3,
        VOL_DESC_SET_TERMINATOR = 255
} vol_desc_type_t;

typedef struct {
        uint8_t system_ident[32];
        uint8_t ident[32];
} __attribute__((packed)) cdfs_vol_desc_boot_t;

typedef struct {
        uint8_t year[4];
        uint8_t mon[2];
        uint8_t day[2];

        uint8_t hour[2];
        uint8_t min[2];
        uint8_t sec[2];
        uint8_t msec[2];

        uint8_t offset;
} __attribute__((packed)) cdfs_datetime_t;

typedef struct {
        uint8_t year;  /**< Since 1900 */
        uint8_t mon;
        uint8_t day;

        uint8_t hour;
        uint8_t min;
        uint8_t sec;

        uint8_t offset;
} __attribute__((packed)) cdfs_timestamp_t;

typedef enum {
        DIR_FLAG_DIRECTORY = 2
} cdfs_dir_flag_t;

/** Directory record */
typedef struct {
        uint8_t length;
        uint8_t ea_length;

        uint32_t_lb lba;
        uint32_t_lb size;

        cdfs_timestamp_t timestamp;
        uint8_t flags;
        uint8_t unit_size;
        uint8_t gap_size;
        uint16_t_lb sequence_nr;

        uint8_t name_length;
        uint8_t name[];
} __attribute__((packed)) cdfs_dir_t;

/** Directory record for the root directory */
typedef struct {
        uint8_t length;
        uint8_t ea_length;

        uint32_t_lb lba;
        uint32_t_lb size;

        cdfs_timestamp_t timestamp;
        uint8_t flags;
        uint8_t unit_size;
        uint8_t gap_size;
        uint16_t_lb sequence_nr;

        uint8_t name_length;
        uint8_t name[1];
} __attribute__((packed)) cdfs_root_dir_t;

typedef struct {
        uint8_t flags; /* reserved in primary */

        uint8_t system_ident[32];
        uint8_t ident[32];

        uint64_t res1;
        uint32_t_lb lba_size;

        uint8_t esc_seq[32]; /* reserved in primary */
        uint16_t_lb set_size;
        uint16_t_lb sequence_nr;

        uint16_t_lb block_size;
        uint32_t_lb path_table_size;

        uint32_t path_table_lsb;
        uint32_t opt_path_table_lsb;
        uint32_t path_table_msb;
        uint32_t opt_path_table_msb;

        cdfs_root_dir_t root_dir;
        uint8_t pad0;

        uint8_t set_ident[128];
        uint8_t publisher_ident[128];
        uint8_t preparer_ident[128];
        uint8_t app_ident[128];

        uint8_t copyright_file_ident[37];
        uint8_t abstract_file_ident[37];
        uint8_t biblio_file_ident[37];

        cdfs_datetime_t creation;
        cdfs_datetime_t modification;
        cdfs_datetime_t expiration;
        cdfs_datetime_t effective;

        uint8_t fs_version;
} __attribute__((packed)) cdfs_vol_desc_prisec_t;

typedef struct {
        uint8_t type;
        uint8_t standard_ident[5];
        uint8_t version;
        union {
                cdfs_vol_desc_boot_t boot;
                cdfs_vol_desc_prisec_t prisec;
        } data;
} __attribute__((packed)) cdfs_vol_desc_t;

typedef enum {
        /** ASCII character set / encoding (base ISO 9660) */
        enc_ascii,
        /** UCS-2 character set / encoding (Joliet) */
        enc_ucs2
} cdfs_enc_t;

typedef enum {
        CDFS_NONE,
        CDFS_FILE,
        CDFS_DIRECTORY
} cdfs_dentry_type_t;

typedef struct {
        link_t link;       /**< Siblings list link */
        fs_index_t index;  /**< Node index */
        char *name;        /**< Dentry name */
} cdfs_dentry_t;

typedef uint32_t cdfs_lba_t;

typedef struct {
        link_t link;              /**< Link to list of all instances */
        service_id_t service_id;  /**< Service ID of block device */
        cdfs_enc_t enc;           /**< Filesystem string encoding */
        char *vol_ident;          /**< Volume identifier */
} cdfs_t;

typedef struct {
        fs_node_t *fs_node;       /**< FS node */
        fs_index_t index;         /**< Node index */
        cdfs_t *fs;               /**< File system */

        ht_link_t nh_link;        /**< Nodes hash table link */
        cdfs_dentry_type_t type;  /**< Dentry type */

        unsigned int lnkcnt;      /**< Link count */
        uint32_t size;            /**< File size if type is CDFS_FILE */

        list_t cs_list;           /**< Child's siblings list */
        cdfs_lba_t lba;           /**< LBA of data on disk */
        bool processed;           /**< If all children have been read */
        unsigned int opened;      /**< Opened count */
} cdfs_node_t;

/** String encoding */
enum {
        /** ASCII - standard ISO 9660 */
        ucs2_esc_seq_no = 3,
        /** USC-2 - Joliet */
        ucs2_esc_seq_len = 3
};

/** Joliet SVD UCS-2 escape sequences */
static uint8_t ucs2_esc_seq[ucs2_esc_seq_no][ucs2_esc_seq_len] = {
        { 0x25, 0x2f, 0x40 },
        { 0x25, 0x2f, 0x43 },
        { 0x25, 0x2f, 0x45 }
};

/** List of all instances */
static LIST_INITIALIZE(cdfs_instances);

/** Shared index of nodes */
static fs_index_t cdfs_index = 1;

/** Number of currently cached nodes */
static size_t nodes_cached = 0;

/** Hash table of all cdfs nodes */
static hash_table_t nodes;

/*
 * Hash table support functions.
 */

typedef struct {
        service_id_t service_id;
        fs_index_t index;
} ht_key_t;

static size_t nodes_key_hash(const void *k)
{
        const ht_key_t *key = k;
        return hash_combine(key->service_id, key->index);
}

static size_t nodes_hash(const ht_link_t *item)
{
        cdfs_node_t *node = hash_table_get_inst(item, cdfs_node_t, nh_link);
        return hash_combine(node->fs->service_id, node->index);
}

static bool nodes_key_equal(const void *k, size_t hash, const ht_link_t *item)
{
        cdfs_node_t *node = hash_table_get_inst(item, cdfs_node_t, nh_link);
        const ht_key_t *key = k;

        return key->service_id == node->fs->service_id && key->index == node->index;
}

static void nodes_remove_callback(ht_link_t *item)
{
        cdfs_node_t *node = hash_table_get_inst(item, cdfs_node_t, nh_link);

        if (node->type == CDFS_DIRECTORY) {
                link_t *link;
                while ((link = list_first(&node->cs_list)) != NULL) {
                        cdfs_dentry_t *dentry = list_get_instance(link, cdfs_dentry_t, link);
                        list_remove(&dentry->link);
                        free(dentry);
                }
        }

        free(node->fs_node);
        free(node);
}

/** Nodes hash table operations */
static const hash_table_ops_t nodes_ops = {
        .hash = nodes_hash,
        .key_hash = nodes_key_hash,
        .key_equal = nodes_key_equal,
        .equal = NULL,
        .remove_callback = nodes_remove_callback
};

static errno_t cdfs_node_get(fs_node_t **rfn, service_id_t service_id,
    fs_index_t index)
{
        ht_key_t key = {
                .index = index,
                .service_id = service_id
        };

        ht_link_t *link = hash_table_find(&nodes, &key);
        if (link) {
                cdfs_node_t *node =
                    hash_table_get_inst(link, cdfs_node_t, nh_link);

                *rfn = FS_NODE(node);
        } else
                *rfn = NULL;

        return EOK;
}

static errno_t cdfs_root_get(fs_node_t **rfn, service_id_t service_id)
{
        return cdfs_node_get(rfn, service_id, CDFS_SOME_ROOT);
}

static void cdfs_node_initialize(cdfs_node_t *node)
{
        node->fs_node = NULL;
        node->index = 0;
        node->fs = NULL;
        node->type = CDFS_NONE;
        node->lnkcnt = 0;
        node->size = 0;
        node->lba = 0;
        node->processed = false;
        node->opened = 0;

        list_initialize(&node->cs_list);
}

static errno_t create_node(fs_node_t **rfn, cdfs_t *fs, int lflag,
    fs_index_t index)
{
        assert((lflag & L_FILE) ^ (lflag & L_DIRECTORY));

        cdfs_node_t *node = malloc(sizeof(cdfs_node_t));
        if (!node)
                return ENOMEM;

        cdfs_node_initialize(node);

        node->fs_node = malloc(sizeof(fs_node_t));
        if (!node->fs_node) {
                free(node);
                return ENOMEM;
        }

        fs_node_initialize(node->fs_node);
        node->fs_node->data = node;

        fs_node_t *rootfn;
        errno_t rc = cdfs_root_get(&rootfn, fs->service_id);

        assert(rc == EOK);

        if (!rootfn)
                node->index = CDFS_SOME_ROOT;
        else
                node->index = index;

        node->fs = fs;

        if (lflag & L_DIRECTORY)
                node->type = CDFS_DIRECTORY;
        else
                node->type = CDFS_FILE;

        /* Insert the new node into the nodes hash table. */
        hash_table_insert(&nodes, &node->nh_link);

        *rfn = FS_NODE(node);
        nodes_cached++;

        return EOK;
}

static errno_t link_node(fs_node_t *pfn, fs_node_t *fn, const char *name)
{
        cdfs_node_t *parent = CDFS_NODE(pfn);
        cdfs_node_t *node = CDFS_NODE(fn);

        assert(parent->type == CDFS_DIRECTORY);

        /* Check for duplicate entries */
        list_foreach(parent->cs_list, link, cdfs_dentry_t, dentry) {
                if (str_cmp(dentry->name, name) == 0)
                        return EEXIST;
        }

        /* Allocate and initialize the dentry */
        cdfs_dentry_t *dentry = malloc(sizeof(cdfs_dentry_t));
        if (!dentry)
                return ENOMEM;

        /* Populate and link the new dentry */
        dentry->name = str_dup(name);
        if (dentry->name == NULL) {
                free(dentry);
                return ENOMEM;
        }

        link_initialize(&dentry->link);
        dentry->index = node->index;

        node->lnkcnt++;
        list_append(&dentry->link, &parent->cs_list);

        return EOK;
}

/** Decode CDFS string.
 *
 * @param data  Pointer to string data
 * @param dsize Size of data in bytes
 * @param enc   String encoding
 * @return      Decoded string
 */
static char *cdfs_decode_str(void *data, size_t dsize, cdfs_enc_t enc)
{
        errno_t rc;
        char *str;
        uint16_t *buf;

        switch (enc) {
        case enc_ascii:
                str = malloc(dsize + 1);
                if (str == NULL)
                        return NULL;
                memcpy(str, data, dsize);
                str[dsize] = '\0';
                break;
        case enc_ucs2:
                buf = calloc(dsize + 2, 1);
                if (buf == NULL)
                        return NULL;

                size_t i;
                for (i = 0; i < dsize / sizeof(uint16_t); i++) {
                        buf[i] = uint16_t_be2host(
                            ((unaligned_uint16_t *)data)[i]);
                }

                size_t dstr_size = dsize / sizeof(uint16_t) * 4 + 1;
                str = malloc(dstr_size);
                if (str == NULL)
                        return NULL;

                rc = utf16_to_str(str, dstr_size, buf);
                free(buf);

                if (rc != EOK)
                        return NULL;
                break;
        default:
                assert(false);
                str = NULL;
        }

        return str;
}

/** Decode file name.
 *
 * @param data  File name buffer
 * @param dsize Fine name buffer size
 * @param enc   Encoding
 * @param dtype Directory entry type
 * @return      Decoded file name (allocated string)
 */
static char *cdfs_decode_name(void *data, size_t dsize, cdfs_enc_t enc,
    cdfs_dentry_type_t dtype)
{
        char *name;
        char *dot;
        char *scolon;

        name = cdfs_decode_str(data, dsize, enc);
        if (name == NULL)
                return NULL;

        if (dtype == CDFS_DIRECTORY)
                return name;

        dot = str_chr(name, '.');

        if (dot != NULL) {
                scolon = str_chr(dot, ';');
                if (scolon != NULL) {
                        /* Trim version part */
                        *scolon = '\0';
                }

                /* If the extension is an empty string, trim the dot separator. */
                if (dot[1] == '\0')
                        *dot = '\0';
        }

        return name;
}

/** Decode volume identifier.
 *
 * @param data  Volume identifier buffer
 * @param dsize Volume identifier buffer size
 * @param enc   Encoding
 * @return      Decoded volume identifier (allocated string)
 */
static char *cdfs_decode_vol_ident(void *data, size_t dsize, cdfs_enc_t enc)
{
        char *ident;
        size_t i;

        ident = cdfs_decode_str(data, dsize, enc);
        if (ident == NULL)
                return NULL;

        /* Trim trailing spaces */
        i = str_size(ident);
        while (i > 0 && ident[i - 1] == ' ')
                --i;
        ident[i] = '\0';

        return ident;
}

static errno_t cdfs_readdir(cdfs_t *fs, fs_node_t *fs_node)
{
        cdfs_node_t *node = CDFS_NODE(fs_node);
        assert(node);

        if (node->processed)
                return EOK;

        uint32_t blocks = node->size / BLOCK_SIZE;
        if ((node->size % BLOCK_SIZE) != 0)
                blocks++;

        for (uint32_t i = 0; i < blocks; i++) {
                block_t *block;
                errno_t rc = block_get(&block, fs->service_id, node->lba + i, BLOCK_FLAGS_NONE);
                if (rc != EOK)
                        return rc;

                cdfs_dir_t *dir;

                for (size_t offset = 0; offset < BLOCK_SIZE;
                    offset += dir->length) {
                        dir = (cdfs_dir_t *) (block->data + offset);
                        if (dir->length == 0)
                                break;
                        if (offset + dir->length > BLOCK_SIZE) {
                                /* XXX Incorrect FS structure */
                                break;
                        }

                        cdfs_dentry_type_t dentry_type;
                        if (dir->flags & DIR_FLAG_DIRECTORY)
                                dentry_type = CDFS_DIRECTORY;
                        else
                                dentry_type = CDFS_FILE;

                        /* Skip special entries */

                        if (dir->name_length == 1 &&
                            dir->name[0] == CDFS_NAME_CURDIR)
                                continue;
                        if (dir->name_length == 1 &&
                            dir->name[0] == CDFS_NAME_PARENTDIR)
                                continue;

                        // FIXME: hack - indexing by dentry byte offset on disc

                        fs_node_t *fn;
                        errno_t rc = create_node(&fn, fs, dentry_type,
                            (node->lba + i) * BLOCK_SIZE + offset);
                        if (rc != EOK)
                                return rc;

                        assert(fn != NULL);

                        cdfs_node_t *cur = CDFS_NODE(fn);
                        cur->lba = uint32_lb(dir->lba);
                        cur->size = uint32_lb(dir->size);

                        char *name = cdfs_decode_name(dir->name,
                            dir->name_length, node->fs->enc, dentry_type);
                        if (name == NULL)
                                return EIO;

                        // FIXME: check return value

                        link_node(fs_node, fn, name);
                        free(name);

                        if (dentry_type == CDFS_FILE)
                                cur->processed = true;
                }

                block_put(block);
        }

        node->processed = true;
        return EOK;
}

static fs_node_t *get_uncached_node(cdfs_t *fs, fs_index_t index)
{
        cdfs_lba_t lba = index / BLOCK_SIZE;
        size_t offset = index % BLOCK_SIZE;

        block_t *block;
        errno_t rc = block_get(&block, fs->service_id, lba, BLOCK_FLAGS_NONE);
        if (rc != EOK)
                return NULL;

        cdfs_dir_t *dir = (cdfs_dir_t *) (block->data + offset);

        cdfs_dentry_type_t dentry_type;
        if (dir->flags & DIR_FLAG_DIRECTORY)
                dentry_type = CDFS_DIRECTORY;
        else
                dentry_type = CDFS_FILE;

        fs_node_t *fn;
        rc = create_node(&fn, fs, dentry_type, index);
        if ((rc != EOK) || (fn == NULL))
                return NULL;

        cdfs_node_t *node = CDFS_NODE(fn);
        node->lba = uint32_lb(dir->lba);
        node->size = uint32_lb(dir->size);
        node->lnkcnt = 1;

        if (dentry_type == CDFS_FILE)
                node->processed = true;

        block_put(block);
        return fn;
}

static fs_node_t *get_cached_node(cdfs_t *fs, fs_index_t index)
{
        ht_key_t key = {
                .index = index,
                .service_id = fs->service_id
        };

        ht_link_t *link = hash_table_find(&nodes, &key);
        if (link) {
                cdfs_node_t *node =
                    hash_table_get_inst(link, cdfs_node_t, nh_link);
                return FS_NODE(node);
        }

        return get_uncached_node(fs, index);
}

static errno_t cdfs_match(fs_node_t **fn, fs_node_t *pfn, const char *component)
{
        cdfs_node_t *parent = CDFS_NODE(pfn);

        if (!parent->processed) {
                errno_t rc = cdfs_readdir(parent->fs, pfn);
                if (rc != EOK)
                        return rc;
        }

        list_foreach(parent->cs_list, link, cdfs_dentry_t, dentry) {
                if (str_cmp(dentry->name, component) == 0) {
                        *fn = get_cached_node(parent->fs, dentry->index);
                        return EOK;
                }
        }

        *fn = NULL;
        return EOK;
}

static errno_t cdfs_node_open(fs_node_t *fn)
{
        cdfs_node_t *node = CDFS_NODE(fn);

        if (!node->processed)
                cdfs_readdir(node->fs, fn);

        node->opened++;
        return EOK;
}

static errno_t cdfs_node_put(fs_node_t *fn)
{
        /* Nothing to do */
        return EOK;
}

static errno_t cdfs_create_node(fs_node_t **fn, service_id_t service_id, int lflag)
{
        /* Read-only */
        return ENOTSUP;
}

static errno_t cdfs_destroy_node(fs_node_t *fn)
{
        /* Read-only */
        return ENOTSUP;
}

static errno_t cdfs_link_node(fs_node_t *pfn, fs_node_t *cfn, const char *name)
{
        /* Read-only */
        return ENOTSUP;
}

static errno_t cdfs_unlink_node(fs_node_t *pfn, fs_node_t *cfn, const char *name)
{
        /* Read-only */
        return ENOTSUP;
}

static errno_t cdfs_has_children(bool *has_children, fs_node_t *fn)
{
        cdfs_node_t *node = CDFS_NODE(fn);

        if ((node->type == CDFS_DIRECTORY) && (!node->processed))
                cdfs_readdir(node->fs, fn);

        *has_children = !list_empty(&node->cs_list);
        return EOK;
}

static fs_index_t cdfs_index_get(fs_node_t *fn)
{
        cdfs_node_t *node = CDFS_NODE(fn);
        return node->index;
}

static aoff64_t cdfs_size_get(fs_node_t *fn)
{
        cdfs_node_t *node = CDFS_NODE(fn);
        return node->size;
}

static unsigned int cdfs_lnkcnt_get(fs_node_t *fn)
{
        cdfs_node_t *node = CDFS_NODE(fn);
        return node->lnkcnt;
}

static bool cdfs_is_directory(fs_node_t *fn)
{
        cdfs_node_t *node = CDFS_NODE(fn);
        return (node->type == CDFS_DIRECTORY);
}

static bool cdfs_is_file(fs_node_t *fn)
{
        cdfs_node_t *node = CDFS_NODE(fn);
        return (node->type == CDFS_FILE);
}

static service_id_t cdfs_service_get(fs_node_t *fn)
{
        return 0;
}

static errno_t cdfs_size_block(service_id_t service_id, uint32_t *size)
{
        *size = BLOCK_SIZE;

        return EOK;
}

static errno_t cdfs_total_block_count(service_id_t service_id, uint64_t *count)
{
        *count = 0;

        return EOK;
}

static errno_t cdfs_free_block_count(service_id_t service_id, uint64_t *count)
{
        *count = 0;

        return EOK;
}

libfs_ops_t cdfs_libfs_ops = {
        .root_get = cdfs_root_get,
        .match = cdfs_match,
        .node_get = cdfs_node_get,
        .node_open = cdfs_node_open,
        .node_put = cdfs_node_put,
        .create = cdfs_create_node,
        .destroy = cdfs_destroy_node,
        .link = cdfs_link_node,
        .unlink = cdfs_unlink_node,
        .has_children = cdfs_has_children,
        .index_get = cdfs_index_get,
        .size_get = cdfs_size_get,
        .lnkcnt_get = cdfs_lnkcnt_get,
        .is_directory = cdfs_is_directory,
        .is_file = cdfs_is_file,
        .service_get = cdfs_service_get,
        .size_block = cdfs_size_block,
        .total_block_count = cdfs_total_block_count,
        .free_block_count = cdfs_free_block_count
};

/** Verify that escape sequence corresonds to one of the allowed encoding
 * escape sequences allowed for Joliet.
 */
static errno_t cdfs_verify_joliet_esc_seq(uint8_t *seq)
{
        size_t i, j, k;
        bool match;

        i = 0;
        while (i + ucs2_esc_seq_len <= 32) {
                if (seq[i] == 0)
                        break;

                for (j = 0; j < ucs2_esc_seq_no; j++) {
                        match = true;
                        for (k = 0; k < ucs2_esc_seq_len; k++)
                                if (seq[i + k] != ucs2_esc_seq[j][k])
                                        match = false;
                        if (match) {
                                break;
                        }
                }

                if (!match)
                        return EINVAL;

                i += ucs2_esc_seq_len;
        }

        while (i < 32) {
                if (seq[i] != 0)
                        return EINVAL;
                ++i;
        }

        return EOK;
}

/** Find Joliet supplementary volume descriptor.
 *
 * @param sid           Block device service ID
 * @param altroot       First filesystem block
 * @param rlba          Place to store LBA of root dir
 * @param rsize         Place to store size of root dir
 * @param vol_ident     Place to store pointer to volume identifier
 * @return              EOK if found, ENOENT if not
 */
static errno_t cdfs_find_joliet_svd(service_id_t sid, cdfs_lba_t altroot,
    uint32_t *rlba, uint32_t *rsize, char **vol_ident)
{
        cdfs_lba_t bi;

        for (bi = altroot + 17; ; bi++) {
                block_t *block;
                errno_t rc = block_get(&block, sid, bi, BLOCK_FLAGS_NONE);
                if (rc != EOK)
                        break;

                cdfs_vol_desc_t *vol_desc = (cdfs_vol_desc_t *) block->data;

                if (vol_desc->type == VOL_DESC_SET_TERMINATOR) {
                        block_put(block);
                        break;
                }

                if ((vol_desc->type != VOL_DESC_SUPPLEMENTARY) ||
                    (memcmp(vol_desc->standard_ident, CDFS_STANDARD_IDENT, 5) != 0) ||
                    (vol_desc->version != 1)) {
                        block_put(block);
                        continue;
                }

                uint16_t set_size = uint16_lb(vol_desc->data.prisec.set_size);
                if (set_size > 1) {
                        /*
                         * Technically, we don't support multi-disc sets.
                         * But one can encounter erroneously mastered
                         * images in the wild and it might actually work
                         * for the first disc in the set.
                         */
                }

                uint16_t sequence_nr = uint16_lb(vol_desc->data.prisec.sequence_nr);
                if (sequence_nr != 1) {
                        /*
                         * We only support the first disc
                         * in multi-disc sets.
                         */
                        block_put(block);
                        continue;
                }

                uint16_t block_size = uint16_lb(vol_desc->data.prisec.block_size);
                if (block_size != BLOCK_SIZE) {
                        block_put(block);
                        continue;
                }

                rc = cdfs_verify_joliet_esc_seq(vol_desc->data.prisec.esc_seq);
                if (rc != EOK)
                        continue;
                *rlba = uint32_lb(vol_desc->data.prisec.root_dir.lba);
                *rsize = uint32_lb(vol_desc->data.prisec.root_dir.size);

                *vol_ident = cdfs_decode_vol_ident(vol_desc->data.prisec.ident,
                    32, enc_ucs2);

                block_put(block);
                return EOK;
        }

        return ENOENT;
}

/** Read the volume descriptors. */
static errno_t iso_read_vol_desc(service_id_t sid, cdfs_lba_t altroot,
    uint32_t *rlba, uint32_t *rsize, cdfs_enc_t *enc, char **vol_ident)
{
        /* First 16 blocks of isofs are empty */
        block_t *block;
        errno_t rc = block_get(&block, sid, altroot + 16, BLOCK_FLAGS_NONE);
        if (rc != EOK)
                return rc;

        cdfs_vol_desc_t *vol_desc = (cdfs_vol_desc_t *) block->data;

        /*
         * Test for primary volume descriptor
         * and standard compliance.
         */
        if ((vol_desc->type != VOL_DESC_PRIMARY) ||
            (memcmp(vol_desc->standard_ident, CDFS_STANDARD_IDENT, 5) != 0) ||
            (vol_desc->version != 1)) {
                block_put(block);
                return ENOTSUP;
        }

        uint16_t set_size = uint16_lb(vol_desc->data.prisec.set_size);
        if (set_size > 1) {
                /*
                 * Technically, we don't support multi-disc sets.
                 * But one can encounter erroneously mastered
                 * images in the wild and it might actually work
                 * for the first disc in the set.
                 */
        }

        uint16_t sequence_nr = uint16_lb(vol_desc->data.prisec.sequence_nr);
        if (sequence_nr != 1) {
                /*
                 * We only support the first disc
                 * in multi-disc sets.
                 */
                block_put(block);
                return ENOTSUP;
        }

        uint16_t block_size = uint16_lb(vol_desc->data.prisec.block_size);
        if (block_size != BLOCK_SIZE) {
                block_put(block);
                return ENOTSUP;
        }

        // TODO: implement path table support

        /* Search for Joliet SVD */

        uint32_t jrlba;
        uint32_t jrsize;

        rc = cdfs_find_joliet_svd(sid, altroot, &jrlba, &jrsize, vol_ident);
        if (rc == EOK) {
                /* Found */
                *rlba = jrlba;
                *rsize = jrsize;
                *enc = enc_ucs2;
        } else {
                *rlba = uint32_lb(vol_desc->data.prisec.root_dir.lba);
                *rsize = uint32_lb(vol_desc->data.prisec.root_dir.size);
                *enc = enc_ascii;
                *vol_ident = cdfs_decode_vol_ident(vol_desc->data.prisec.ident,
                    32, enc_ascii);
        }

        block_put(block);
        return EOK;
}

static errno_t iso_readfs(cdfs_t *fs, fs_node_t *rfn,
    cdfs_lba_t altroot)
{
        cdfs_node_t *node = CDFS_NODE(rfn);

        errno_t rc = iso_read_vol_desc(fs->service_id, altroot, &node->lba,
            &node->size, &fs->enc, &fs->vol_ident);
        if (rc != EOK)
                return rc;

        return cdfs_readdir(fs, rfn);
}

/*
 * Mount a session with session start offset
 *
 */
static cdfs_t *cdfs_fs_create(service_id_t sid, cdfs_lba_t altroot)
{
        cdfs_t *fs = NULL;
        fs_node_t *rfn = NULL;

        fs = calloc(1, sizeof(cdfs_t));
        if (fs == NULL)
                goto error;

        fs->service_id = sid;

        /* Create root node */
        errno_t rc = create_node(&rfn, fs, L_DIRECTORY, cdfs_index++);

        if ((rc != EOK) || (!rfn))
                goto error;

        /* FS root is not linked */
        CDFS_NODE(rfn)->lnkcnt = 0;
        CDFS_NODE(rfn)->lba = 0;
        CDFS_NODE(rfn)->processed = false;

        /* Check if there is cdfs in given session */
        if (iso_readfs(fs, rfn, altroot) != EOK)
                goto error;

        list_append(&fs->link, &cdfs_instances);
        return fs;
error:
        // XXX destroy node
        free(fs);
        return NULL;
}

static errno_t cdfs_fsprobe(service_id_t service_id, vfs_fs_probe_info_t *info)
{
        char *vol_ident;

        /* Initialize the block layer */
        errno_t rc = block_init(service_id);
        if (rc != EOK)
                return rc;

        cdfs_lba_t altroot = 0;

        /*
         * Read TOC multisession information and get the start address
         * of the first track in the last session
         */
        scsi_toc_multisess_data_t toc;

        rc = block_read_toc(service_id, 1, &toc, sizeof(toc));
        if (rc == EOK && (uint16_t_be2host(toc.toc_len) == 10))
                altroot = uint32_t_be2host(toc.ftrack_lsess.start_addr);

        /* Initialize the block cache */
        rc = block_cache_init(service_id, BLOCK_SIZE, 0, CACHE_MODE_WT);
        if (rc != EOK) {
                block_fini(service_id);
                return rc;
        }

        /* Check if this device is not already mounted */
        fs_node_t *rootfn;
        rc = cdfs_root_get(&rootfn, service_id);
        if ((rc == EOK) && (rootfn)) {
                cdfs_node_put(rootfn);
                block_cache_fini(service_id);
                block_fini(service_id);
                return EOK;
        }

        /* Read volume descriptors */
        uint32_t rlba;
        uint32_t rsize;
        cdfs_enc_t enc;
        rc = iso_read_vol_desc(service_id, altroot, &rlba, &rsize, &enc,
            &vol_ident);
        if (rc != EOK) {
                block_cache_fini(service_id);
                block_fini(service_id);
                return rc;
        }

        str_cpy(info->label, FS_LABEL_MAXLEN + 1, vol_ident);
        free(vol_ident);

        block_cache_fini(service_id);
        block_fini(service_id);
        return EOK;
}

static errno_t cdfs_mounted(service_id_t service_id, const char *opts,
    fs_index_t *index, aoff64_t *size)
{
        /* Initialize the block layer */
        errno_t rc = block_init(service_id);
        if (rc != EOK)
                return rc;

        cdfs_lba_t altroot = 0;

        if (str_lcmp(opts, "altroot=", 8) == 0) {
                /* User-defined alternative root on a multi-session disk */
                if (str_uint32_t(opts + 8, NULL, 0, false, &altroot) != EOK)
                        altroot = 0;
        } else {
                /*
                 * Read TOC multisession information and get the start address
                 * of the first track in the last session
                 */
                scsi_toc_multisess_data_t toc;

                rc = block_read_toc(service_id, 1, &toc, sizeof(toc));
                if (rc == EOK && (uint16_t_be2host(toc.toc_len) == 10))
                        altroot = uint32_t_be2host(toc.ftrack_lsess.start_addr);
        }

        /* Initialize the block cache */
        rc = block_cache_init(service_id, BLOCK_SIZE, 0, CACHE_MODE_WT);
        if (rc != EOK) {
                block_fini(service_id);
                return rc;
        }

        /* Check if this device is not already mounted */
        fs_node_t *rootfn;
        rc = cdfs_root_get(&rootfn, service_id);
        if ((rc == EOK) && (rootfn)) {
                cdfs_node_put(rootfn);
                block_cache_fini(service_id);
                block_fini(service_id);

                return EEXIST;
        }

        /* Create cdfs instance */
        if (cdfs_fs_create(service_id, altroot) == NULL) {
                block_cache_fini(service_id);
                block_fini(service_id);

                return ENOMEM;
        }

        rc = cdfs_root_get(&rootfn, service_id);
        assert(rc == EOK);

        cdfs_node_t *root = CDFS_NODE(rootfn);
        *index = root->index;
        *size = root->size;

        return EOK;
}

static bool rm_service_id_nodes(ht_link_t *item, void *arg)
{
        service_id_t service_id = *(service_id_t *)arg;
        cdfs_node_t *node = hash_table_get_inst(item, cdfs_node_t, nh_link);

        if (node->fs->service_id == service_id) {
                hash_table_remove_item(&nodes, &node->nh_link);
        }

        return true;
}

static void cdfs_fs_destroy(cdfs_t *fs)
{
        list_remove(&fs->link);
        hash_table_apply(&nodes, rm_service_id_nodes, &fs->service_id);
        block_cache_fini(fs->service_id);
        block_fini(fs->service_id);
        free(fs->vol_ident);
        free(fs);
}

static cdfs_t *cdfs_find_by_sid(service_id_t service_id)
{
        list_foreach(cdfs_instances, link, cdfs_t, fs) {
                if (fs->service_id == service_id)
                        return fs;
        }

        return NULL;
}

static errno_t cdfs_unmounted(service_id_t service_id)
{
        cdfs_t *fs;

        fs = cdfs_find_by_sid(service_id);
        if (fs == NULL)
                return ENOENT;

        cdfs_fs_destroy(fs);
        return EOK;
}

static errno_t cdfs_read(service_id_t service_id, fs_index_t index, aoff64_t pos,
    size_t *rbytes)
{
        ht_key_t key = {
                .index = index,
                .service_id = service_id
        };

        ht_link_t *link = hash_table_find(&nodes, &key);
        if (link == NULL)
                return ENOENT;

        cdfs_node_t *node =
            hash_table_get_inst(link, cdfs_node_t, nh_link);

        if (!node->processed) {
                errno_t rc = cdfs_readdir(node->fs, FS_NODE(node));
                if (rc != EOK)
                        return rc;
        }

        ipc_call_t call;
        size_t len;
        if (!async_data_read_receive(&call, &len)) {
                async_answer_0(&call, EINVAL);
                return EINVAL;
        }

        if (node->type == CDFS_FILE) {
                if (pos >= node->size) {
                        *rbytes = 0;
                        async_data_read_finalize(&call, NULL, 0);
                } else {
                        cdfs_lba_t lba = pos / BLOCK_SIZE;
                        size_t offset = pos % BLOCK_SIZE;

                        *rbytes = min(len, BLOCK_SIZE - offset);
                        *rbytes = min(*rbytes, node->size - pos);

                        block_t *block;
                        errno_t rc = block_get(&block, service_id, node->lba + lba,
                            BLOCK_FLAGS_NONE);
                        if (rc != EOK) {
                                async_answer_0(&call, rc);
                                return rc;
                        }

                        async_data_read_finalize(&call, block->data + offset,
                            *rbytes);
                        rc = block_put(block);
                        if (rc != EOK)
                                return rc;
                }
        } else {
                link_t *link = list_nth(&node->cs_list, pos);
                if (link == NULL) {
                        async_answer_0(&call, ENOENT);
                        return ENOENT;
                }

                cdfs_dentry_t *dentry =
                    list_get_instance(link, cdfs_dentry_t, link);

                *rbytes = 1;
                async_data_read_finalize(&call, dentry->name,
                    str_size(dentry->name) + 1);
        }

        return EOK;
}

static errno_t cdfs_write(service_id_t service_id, fs_index_t index, aoff64_t pos,
    size_t *wbytes, aoff64_t *nsize)
{
        /*
         * As cdfs is a read-only filesystem,
         * the operation is not supported.
         */

        return ENOTSUP;
}

static errno_t cdfs_truncate(service_id_t service_id, fs_index_t index,
    aoff64_t size)
{
        /*
         * As cdfs is a read-only filesystem,
         * the operation is not supported.
         */

        return ENOTSUP;
}

static bool cache_remove_closed(ht_link_t *item, void *arg)
{
        size_t *premove_cnt = (size_t *)arg;

        /* Some nodes were requested to be removed from the cache. */
        if (0 < *premove_cnt) {
                cdfs_node_t *node = hash_table_get_inst(item, cdfs_node_t, nh_link);

                if (!node->opened) {
                        hash_table_remove_item(&nodes, item);

                        --nodes_cached;
                        --*premove_cnt;
                }
        }

        /* Only continue if more nodes were requested to be removed. */
        return 0 < *premove_cnt;
}

static void cleanup_cache(service_id_t service_id)
{
        if (nodes_cached > NODE_CACHE_SIZE) {
                size_t remove_cnt = nodes_cached - NODE_CACHE_SIZE;

                if (0 < remove_cnt)
                        hash_table_apply(&nodes, cache_remove_closed, &remove_cnt);
        }
}

static errno_t cdfs_close(service_id_t service_id, fs_index_t index)
{
        /* Root node is always in memory */
        if (index == 0)
                return EOK;

        ht_key_t key = {
                .index = index,
                .service_id = service_id
        };

        ht_link_t *link = hash_table_find(&nodes, &key);
        if (link == 0)
                return ENOENT;

        cdfs_node_t *node =
            hash_table_get_inst(link, cdfs_node_t, nh_link);

        assert(node->opened > 0);

        node->opened--;
        cleanup_cache(service_id);

        return EOK;
}

static errno_t cdfs_destroy(service_id_t service_id, fs_index_t index)
{
        /*
         * As cdfs is a read-only filesystem,
         * the operation is not supported.
         */

        return ENOTSUP;
}

static errno_t cdfs_sync(service_id_t service_id, fs_index_t index)
{
        /*
         * As cdfs is a read-only filesystem,
         * the sync operation is a no-op.
         */

        return EOK;
}

vfs_out_ops_t cdfs_ops = {
        .fsprobe = cdfs_fsprobe,
        .mounted = cdfs_mounted,
        .unmounted = cdfs_unmounted,
        .read = cdfs_read,
        .write = cdfs_write,
        .truncate = cdfs_truncate,
        .close = cdfs_close,
        .destroy = cdfs_destroy,
        .sync = cdfs_sync
};

/** Initialize the cdfs server
 *
 */
bool cdfs_init(void)
{
        if (!hash_table_create(&nodes, 0, 0, &nodes_ops))
                return false;

        return true;
}

/**
 * @}
 */