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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    tmpfs_ops.c

 * @brief   Implementation of VFS operations for the TMPFS file system

 *      server.

 */

#include "tmpfs.h"

#include "../../vfs/vfs.h"

#include <ipc/ipc.h>

#include <async.h>

#include <errno.h>

#include <atomic.h>

#include <stdlib.h>

#include <string.h>

#include <stdio.h>

#include <assert.h>

#include <sys/types.h>

#include <adt/hash_table.h>

#include <as.h>

#include <libfs.h>

#define min(a, b)       ((a) < (b) ? (a) : (b))

#define max(a, b)       ((a) > (b) ? (a) : (b))

#define NODES_BUCKETS   256

/** All root nodes have index 0. */

#define TMPFS_SOME_ROOT     0

/** Global counter for assigning node indices. Shared by all instances. */

fs_index_t tmpfs_next_index = 1;

/*

 * Implementation of the libfs interface.

 */

/* Forward declarations of static functions. */

static fs_node_t *tmpfs_match(fs_node_t *, const char *);

static fs_node_t *tmpfs_node_get(dev_handle_t, fs_index_t);

static void tmpfs_node_put(fs_node_t *);

static fs_node_t *tmpfs_create_node(dev_handle_t, int);

static int tmpfs_link_node(fs_node_t *, fs_node_t *, const char *);

static int tmpfs_unlink_node(fs_node_t *, fs_node_t *, const char *);

static int tmpfs_destroy_node(fs_node_t *);

/* Implementation of helper functions. */

static fs_index_t tmpfs_index_get(fs_node_t *fn)

{

    return TMPFS_NODE(fn)->index;

}

static size_t tmpfs_size_get(fs_node_t *fn)

{

    return TMPFS_NODE(fn)->size;

}

static unsigned tmpfs_lnkcnt_get(fs_node_t *fn)

{

    return TMPFS_NODE(fn)->lnkcnt;

}

static bool tmpfs_has_children(fs_node_t *fn)

{

    return !list_empty(&TMPFS_NODE(fn)->cs_head);

}

static fs_node_t *tmpfs_root_get(dev_handle_t dev_handle)

{

    return tmpfs_node_get(dev_handle, TMPFS_SOME_ROOT);

}

static char tmpfs_plb_get_char(unsigned pos)

{

    return tmpfs_reg.plb_ro[pos % PLB_SIZE];

}

static bool tmpfs_is_directory(fs_node_t *fn)

{

    return TMPFS_NODE(fn)->type == TMPFS_DIRECTORY;

}

static bool tmpfs_is_file(fs_node_t *fn)

{

    return TMPFS_NODE(fn)->type == TMPFS_FILE;

}

/** libfs operations */

libfs_ops_t tmpfs_libfs_ops = {

    .match = tmpfs_match,

    .node_get = tmpfs_node_get,

    .node_put = tmpfs_node_put,

    .create = tmpfs_create_node,

    .destroy = tmpfs_destroy_node,

    .link = tmpfs_link_node,

    .unlink = tmpfs_unlink_node,

    .index_get = tmpfs_index_get,

    .size_get = tmpfs_size_get,

    .lnkcnt_get = tmpfs_lnkcnt_get,

    .has_children = tmpfs_has_children,

    .root_get = tmpfs_root_get,

    .plb_get_char = tmpfs_plb_get_char,

    .is_directory = tmpfs_is_directory,

    .is_file = tmpfs_is_file

};

/** Hash table of all TMPFS nodes. */

hash_table_t nodes;

#define NODES_KEY_INDEX 0

#define NODES_KEY_DEV   1

/* Implementation of hash table interface for the nodes hash table. */

static hash_index_t nodes_hash(unsigned long key[])

{

    return key[NODES_KEY_INDEX] % NODES_BUCKETS;

}

static int nodes_compare(unsigned long key[], hash_count_t keys, link_t *item)

{

    tmpfs_node_t *nodep = hash_table_get_instance(item, tmpfs_node_t,

        nh_link);

    return (nodep->index == key[NODES_KEY_INDEX] &&

        nodep->dev_handle == key[NODES_KEY_DEV]);

}

static void nodes_remove_callback(link_t *item)

{

}

/** TMPFS nodes hash table operations. */

hash_table_operations_t nodes_ops = {

    .hash = nodes_hash,

    .compare = nodes_compare,

    .remove_callback = nodes_remove_callback

};

static void tmpfs_node_initialize(tmpfs_node_t *nodep)

{

    nodep->bp = NULL;

    nodep->index = 0;

    nodep->dev_handle = 0;

    nodep->type = TMPFS_NONE;

    nodep->lnkcnt = 0;

    nodep->size = 0;

    nodep->data = NULL;

    link_initialize(&nodep->nh_link);

    list_initialize(&nodep->cs_head);

}

static void tmpfs_dentry_initialize(tmpfs_dentry_t *dentryp)

{

    link_initialize(&dentryp->link);

    dentryp->name = NULL;

    dentryp->node = NULL;

}

bool tmpfs_init(void)

{

    if (!hash_table_create(&nodes, NODES_BUCKETS, 2, &nodes_ops))

        return false;

    return true;

}

static bool tmpfs_instance_init(dev_handle_t dev_handle)

{

    fs_node_t *rfn;

    rfn = tmpfs_create_node(dev_handle, L_DIRECTORY);

    if (!rfn)

        return false;

    TMPFS_NODE(rfn)->lnkcnt = 0;    /* FS root is not linked */

    return true;

}

fs_node_t *tmpfs_match(fs_node_t *pfn, const char *component)

{

    tmpfs_node_t *parentp = TMPFS_NODE(pfn);

    link_t *lnk;

    for (lnk = parentp->cs_head.next; lnk != &parentp->cs_head;

        lnk = lnk->next) {

        tmpfs_dentry_t *dentryp = list_get_instance(lnk, tmpfs_dentry_t,

            link);

        if (!str_cmp(dentryp->name, component))

            return FS_NODE(dentryp->node);

    }

    return NULL;

}

fs_node_t *tmpfs_node_get(dev_handle_t dev_handle, fs_index_t index)

{

    unsigned long key[] = {

        [NODES_KEY_INDEX] = index,

        [NODES_KEY_DEV] = dev_handle

    };

    link_t *lnk = hash_table_find(&nodes, key);

    if (!lnk)

        return NULL;

    return FS_NODE(hash_table_get_instance(lnk, tmpfs_node_t, nh_link));

}

void tmpfs_node_put(fs_node_t *fn)

{

    /* nothing to do */

}

fs_node_t *tmpfs_create_node(dev_handle_t dev_handle, int lflag)

{

    assert((lflag & L_FILE) ^ (lflag & L_DIRECTORY));

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

    if (!nodep)

        return NULL;

    tmpfs_node_initialize(nodep);

    nodep->bp = malloc(sizeof(fs_node_t));

    if (!nodep->bp) {

        free(nodep);

        return NULL;

    }

    fs_node_initialize(nodep->bp);

    nodep->bp->data = nodep;    /* link the FS and TMPFS nodes */

    if (!tmpfs_root_get(dev_handle))

        nodep->index = TMPFS_SOME_ROOT;

    else

        nodep->index = tmpfs_next_index++;

    nodep->dev_handle = dev_handle;

    if (lflag & L_DIRECTORY)

        nodep->type = TMPFS_DIRECTORY;

    else

        nodep->type = TMPFS_FILE;

    /* Insert the new node into the nodes hash table. */

    unsigned long key[] = {

        [NODES_KEY_INDEX] = nodep->index,

        [NODES_KEY_DEV] = nodep->dev_handle

    };

    hash_table_insert(&nodes, key, &nodep->nh_link);

    return FS_NODE(nodep);

}

int tmpfs_link_node(fs_node_t *pfn, fs_node_t *cfn, const char *nm)

{

    tmpfs_node_t *parentp = TMPFS_NODE(pfn);

    tmpfs_node_t *childp = TMPFS_NODE(cfn);

    tmpfs_dentry_t *dentryp;

    link_t *lnk;

    assert(parentp->type == TMPFS_DIRECTORY);

    /* Check for duplicit entries. */

    for (lnk = parentp->cs_head.next; lnk != &parentp->cs_head;

        lnk = lnk->next) {

        dentryp = list_get_instance(lnk, tmpfs_dentry_t, link);

        if (!str_cmp(dentryp->name, nm))

            return EEXIST;

    }

    /* Allocate and initialize the dentry. */

    dentryp = malloc(sizeof(tmpfs_dentry_t));

    if (!dentryp)

        return ENOMEM;

    tmpfs_dentry_initialize(dentryp);

    /* Populate and link the new dentry. */

    size_t size = str_size(nm);

    dentryp->name = malloc(size + 1);

    if (!dentryp->name) {

        free(dentryp);

        return ENOMEM;

    }

    str_cpy(dentryp->name, size + 1, nm);

    dentryp->node = childp;

    childp->lnkcnt++;

    list_append(&dentryp->link, &parentp->cs_head);

    return EOK;

}

int tmpfs_unlink_node(fs_node_t *pfn, fs_node_t *cfn, const char *nm)

{

    tmpfs_node_t *parentp = TMPFS_NODE(pfn);

    tmpfs_node_t *childp = NULL;

    tmpfs_dentry_t *dentryp;

    link_t *lnk;

    if (!parentp)

        return EBUSY;

    for (lnk = parentp->cs_head.next; lnk != &parentp->cs_head;

        lnk = lnk->next) {

        dentryp = list_get_instance(lnk, tmpfs_dentry_t, link);

        if (!str_cmp(dentryp->name, nm)) {

            childp = dentryp->node;

            assert(FS_NODE(childp) == cfn);

            break;

        }  

    }

    if (!childp)

        return ENOENT;

    if ((childp->lnkcnt == 1) && !list_empty(&childp->cs_head))

        return ENOTEMPTY;

    list_remove(&dentryp->link);

    free(dentryp);

    childp->lnkcnt--;

    return EOK;

}

int tmpfs_destroy_node(fs_node_t *fn)

{

    tmpfs_node_t *nodep = TMPFS_NODE(fn);

    assert(!nodep->lnkcnt);

    assert(list_empty(&nodep->cs_head));

    unsigned long key[] = {

        [NODES_KEY_INDEX] = nodep->index,

        [NODES_KEY_DEV] = nodep->dev_handle

    };

    hash_table_remove(&nodes, key, 2);

    if (nodep->type == TMPFS_FILE)

        free(nodep->data);

    free(nodep->bp);

    free(nodep);

    return EOK;

}

void tmpfs_mounted(ipc_callid_t rid, ipc_call_t *request)

{

    dev_handle_t dev_handle = (dev_handle_t) IPC_GET_ARG1(*request);

    /* accept the mount options */

    ipc_callid_t callid;

    size_t size;

    if (!ipc_data_write_receive(&callid, &size)) {

        ipc_answer_0(callid, EINVAL);

        ipc_answer_0(rid, EINVAL);

        return;

    }

    char *opts = malloc(size + 1);

    if (!opts) {

        ipc_answer_0(callid, ENOMEM);

        ipc_answer_0(rid, ENOMEM);

        return;

    }

    ipcarg_t retval = ipc_data_write_finalize(callid, opts, size);

    if (retval != EOK) {

        ipc_answer_0(rid, retval);

        free(opts);

        return;

    }

    opts[size] = '\0';

    /* Initialize TMPFS instance. */

    if (!tmpfs_instance_init(dev_handle)) {

        ipc_answer_0(rid, ENOMEM);

        return;

    }

    tmpfs_node_t *rootp = TMPFS_NODE(tmpfs_root_get(dev_handle));

    if (str_cmp(opts, "restore") == 0) {

        if (tmpfs_restore(dev_handle))

            ipc_answer_3(rid, EOK, rootp->index, rootp->size,

                rootp->lnkcnt);

        else

            ipc_answer_0(rid, ELIMIT);

    } else {

        ipc_answer_3(rid, EOK, rootp->index, rootp->size,

            rootp->lnkcnt);

    }

}

void tmpfs_mount(ipc_callid_t rid, ipc_call_t *request)

{

    libfs_mount(&tmpfs_libfs_ops, tmpfs_reg.fs_handle, rid, request);

}

void tmpfs_lookup(ipc_callid_t rid, ipc_call_t *request)

{

    libfs_lookup(&tmpfs_libfs_ops, tmpfs_reg.fs_handle, rid, request);

}

void tmpfs_read(ipc_callid_t rid, ipc_call_t *request)

{

    dev_handle_t dev_handle = (dev_handle_t)IPC_GET_ARG1(*request);

    fs_index_t index = (fs_index_t)IPC_GET_ARG2(*request);

    off_t pos = (off_t)IPC_GET_ARG3(*request);

    /*

     * Lookup the respective TMPFS node.

     */

    link_t *hlp;

    unsigned long key[] = {

        [NODES_KEY_INDEX] = index,

        [NODES_KEY_DEV] = dev_handle,

    };

    hlp = hash_table_find(&nodes, key);

    if (!hlp) {

        ipc_answer_0(rid, ENOENT);

        return;

    }

    tmpfs_node_t *nodep = hash_table_get_instance(hlp, tmpfs_node_t,

        nh_link);

    /*

     * Receive the read request.

     */

    ipc_callid_t callid;

    size_t size;

    if (!ipc_data_read_receive(&callid, &size)) {

        ipc_answer_0(callid, EINVAL);  

        ipc_answer_0(rid, EINVAL);

        return;

    }

    size_t bytes;

    if (nodep->type == TMPFS_FILE) {

        bytes = max(0, min(nodep->size - pos, size));

        (void) ipc_data_read_finalize(callid, nodep->data + pos,

            bytes);

    } else {

        tmpfs_dentry_t *dentryp;

        link_t *lnk;

        int i;

        assert(nodep->type == TMPFS_DIRECTORY);

        /*

         * Yes, we really use O(n) algorithm here.

         * If it bothers someone, it could be fixed by introducing a

         * hash table.

         */

        for (i = 0, lnk = nodep->cs_head.next;

            i < pos && lnk != &nodep->cs_head;

            i++, lnk = lnk->next)

            ;

        if (lnk == &nodep->cs_head) {

            ipc_answer_0(callid, ENOENT);

            ipc_answer_1(rid, ENOENT, 0);

            return;

        }

        dentryp = list_get_instance(lnk, tmpfs_dentry_t, link);

        (void) ipc_data_read_finalize(callid, dentryp->name,

            str_size(dentryp->name) + 1);

        bytes = 1;

    }

    /*

     * Answer the VFS_READ call.

     */

    ipc_answer_1(rid, EOK, bytes);

}

void tmpfs_write(ipc_callid_t rid, ipc_call_t *request)

{

    dev_handle_t dev_handle = (dev_handle_t)IPC_GET_ARG1(*request);

    fs_index_t index = (fs_index_t)IPC_GET_ARG2(*request);

    off_t pos = (off_t)IPC_GET_ARG3(*request);

    /*

     * Lookup the respective TMPFS node.

     */

    link_t *hlp;

    unsigned long key[] = {

        [NODES_KEY_INDEX] = index,

        [NODES_KEY_DEV] = dev_handle

    };

    hlp = hash_table_find(&nodes, key);

    if (!hlp) {

        ipc_answer_0(rid, ENOENT);

        return;

    }

    tmpfs_node_t *nodep = hash_table_get_instance(hlp, tmpfs_node_t,

        nh_link);

    /*

     * Receive the write request.

     */

    ipc_callid_t callid;

    size_t size;

    if (!ipc_data_write_receive(&callid, &size)) {

        ipc_answer_0(callid, EINVAL);  

        ipc_answer_0(rid, EINVAL);

        return;

    }

    /*

     * Check whether the file needs to grow.

     */

    if (pos + size <= nodep->size) {

        /* The file size is not changing. */

        (void) ipc_data_write_finalize(callid, nodep->data + pos, size);

        ipc_answer_2(rid, EOK, size, nodep->size);

        return;

    }

    size_t delta = (pos + size) - nodep->size;

    /*

     * At this point, we are deliberately extremely straightforward and

     * simply realloc the contents of the file on every write that grows the

     * file. In the end, the situation might not be as bad as it may look:

     * our heap allocator can save us and just grow the block whenever

     * possible.

     */

    void *newdata = realloc(nodep->data, nodep->size + delta);

    if (!newdata) {

        ipc_answer_0(callid, ENOMEM);

        ipc_answer_2(rid, EOK, 0, nodep->size);

        return;

    }

    /* Clear any newly allocated memory in order to emulate gaps. */

    memset(newdata + nodep->size, 0, delta);

    nodep->size += delta;

    nodep->data = newdata;

    (void) ipc_data_write_finalize(callid, nodep->data + pos, size);

    ipc_answer_2(rid, EOK, size, nodep->size);

}

void tmpfs_truncate(ipc_callid_t rid, ipc_call_t *request)

{

    dev_handle_t dev_handle = (dev_handle_t)IPC_GET_ARG1(*request);

    fs_index_t index = (fs_index_t)IPC_GET_ARG2(*request);

    size_t size = (off_t)IPC_GET_ARG3(*request);

    /*

     * Lookup the respective TMPFS node.

     */

    link_t *hlp;

    unsigned long key[] = {

        [NODES_KEY_INDEX] = index,

        [NODES_KEY_DEV] = dev_handle

    };

    hlp = hash_table_find(&nodes, key);

    if (!hlp) {

        ipc_answer_0(rid, ENOENT);

        return;

    }

    tmpfs_node_t *nodep = hash_table_get_instance(hlp, tmpfs_node_t,

        nh_link);

    if (size == nodep->size) {

        ipc_answer_0(rid, EOK);

        return;

    }

    void *newdata = realloc(nodep->data, size);

    if (!newdata) {

        ipc_answer_0(rid, ENOMEM);

        return;

    }

    if (size > nodep->size) {

        size_t delta = size - nodep->size;

        memset(newdata + nodep->size, 0, delta);

    }

    nodep->size = size;

    nodep->data = newdata;

    ipc_answer_0(rid, EOK);

}

void tmpfs_close(ipc_callid_t rid, ipc_call_t *request)

{

    ipc_answer_0(rid, EOK);

}

void tmpfs_destroy(ipc_callid_t rid, ipc_call_t *request)

{

    dev_handle_t dev_handle = (dev_handle_t)IPC_GET_ARG1(*request);

    fs_index_t index = (fs_index_t)IPC_GET_ARG2(*request);

    int rc;

    link_t *hlp;

    unsigned long key[] = {

        [NODES_KEY_INDEX] = index,

        [NODES_KEY_DEV] = dev_handle

    };

    hlp = hash_table_find(&nodes, key);

    if (!hlp) {

        ipc_answer_0(rid, ENOENT);

        return;

    }

    tmpfs_node_t *nodep = hash_table_get_instance(hlp, tmpfs_node_t,

        nh_link);

    rc = tmpfs_destroy_node(FS_NODE(nodep));

    ipc_answer_0(rid, rc);

}

void tmpfs_open_node(ipc_callid_t rid, ipc_call_t *request)

{

    libfs_open_node(&tmpfs_libfs_ops, tmpfs_reg.fs_handle, rid, request);

}

void tmpfs_stat(ipc_callid_t rid, ipc_call_t *request)

{

    libfs_stat(&tmpfs_libfs_ops, tmpfs_reg.fs_handle, rid, request);

}

void tmpfs_sync(ipc_callid_t rid, ipc_call_t *request)

{

    /* Dummy implementation */

    ipc_answer_0(rid, EOK);

}

/**

 * @}

 */