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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 <libadt/hash_table.h>

#include <as.h>

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

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

#define PLB_GET_CHAR(i)     (tmpfs_reg.plb_ro[(i) % PLB_SIZE])

#define DENTRIES_BUCKETS    256

/*

 * Hash table of all directory entries.

 */

hash_table_t dentries;

static hash_index_t dentries_hash(unsigned long *key)

{

    return *key % DENTRIES_BUCKETS;

}

static int dentries_compare(unsigned long *key, hash_count_t keys,

    link_t *item)

{

    tmpfs_dentry_t *dentry = hash_table_get_instance(item, tmpfs_dentry_t,

        dh_link);

    return dentry->index == *key;

}

static void dentries_remove_callback(link_t *item)

{

}

/** TMPFS dentries hash table operations. */

hash_table_operations_t dentries_ops = {

    .hash = dentries_hash,

    .compare = dentries_compare,

    .remove_callback = dentries_remove_callback

};

unsigned tmpfs_next_index = 1;

static void tmpfs_dentry_initialize(tmpfs_dentry_t *dentry)

{

    dentry->index = 0;

    dentry->parent = NULL;

    dentry->sibling = NULL;

    dentry->child = NULL;

    dentry->name = NULL;

    dentry->type = TMPFS_NONE;

    dentry->size = 0;

    dentry->data = NULL;

    link_initialize(&dentry->dh_link);

}

/*

 * For now, we don't distinguish between different dev_handles/instances. All

 * requests resolve to the only instance, rooted in the following variable.

 */

static tmpfs_dentry_t *root;

static bool tmpfs_init(void)

{

    if (!hash_table_create(&dentries, DENTRIES_BUCKETS, 1, &dentries_ops))

        return false;

    root = (tmpfs_dentry_t *) malloc(sizeof(tmpfs_dentry_t));

    if (!root)

        return false;

    tmpfs_dentry_initialize(root);

    root->index = tmpfs_next_index++;

    root->name = "";

    root->type = TMPFS_DIRECTORY;

    hash_table_insert(&dentries, &root->index, &root->dh_link);

    /*

     * This is only for debugging. Once we can create files and directories

     * using VFS, we can get rid of this.

     */

    tmpfs_dentry_t *d;

    d = (tmpfs_dentry_t *) malloc(sizeof(tmpfs_dentry_t));

    if (!d) {

        free(root);

        root = NULL;

        return false;

    }

    tmpfs_dentry_initialize(d);

    d->index = tmpfs_next_index++;

    root->child = d;

    d->parent = root;

    d->type = TMPFS_DIRECTORY;

    d->name = "dir1";

    hash_table_insert(&dentries, &d->index, &d->dh_link);

    d = (tmpfs_dentry_t *) malloc(sizeof(tmpfs_dentry_t));

    if (!d) {

        free(root->child);

        free(root);

        root = NULL;

        return false;

    }

    tmpfs_dentry_initialize(d);

    d->index = tmpfs_next_index++;

    root->child->sibling = d;

    d->parent = root;

    d->type = TMPFS_DIRECTORY;

    d->name = "dir2";

    hash_table_insert(&dentries, &d->index, &d->dh_link);

    d = (tmpfs_dentry_t *) malloc(sizeof(tmpfs_dentry_t));

    if (!d) {

        free(root->child->sibling);

        free(root->child);

        free(root);

        root = NULL;

        return false;

    }

    tmpfs_dentry_initialize(d);

    d->index = tmpfs_next_index++;

    root->child->child = d;

    d->parent = root->child;

    d->type = TMPFS_FILE;

    d->name = "file1";

    d->data = "This is the contents of /dir1/file1.\n";

    d->size = strlen(d->data);

    hash_table_insert(&dentries, &d->index, &d->dh_link);

    d = (tmpfs_dentry_t *) malloc(sizeof(tmpfs_dentry_t));

    if (!d) {

        free(root->child->sibling);

        free(root->child->child);

        free(root->child);

        free(root);

        root = NULL;

        return false;

    }

    tmpfs_dentry_initialize(d);

    d->index = tmpfs_next_index++;

    root->child->sibling->child = d;

    d->parent = root->child->sibling;

    d->type = TMPFS_FILE;

    d->name = "file2";

    d->data = "This is the contents of /dir2/file2.\n";

    d->size = strlen(d->data);

    hash_table_insert(&dentries, &d->index, &d->dh_link);

    return true;

}

/** Compare one component of path to a directory entry.

 *

 * @param dentry    Directory entry to compare the path component with.

 * @param start     Index into PLB where the path component starts.

 * @param last      Index of the last character of the path in PLB.

 *

 * @return      Zero on failure or delta such that (index + delta) %

 *          PLB_SIZE points to the first unprocessed character in

 *          PLB which comprises the path.

 */

static unsigned match_path_component(tmpfs_dentry_t *dentry, unsigned start,

    unsigned last)

{

    int i, j;

    size_t namelen;

    namelen = strlen(dentry->name);

    if (last < start)

        last += PLB_SIZE;

    for (i = 0, j = start; i < namelen && j <= last; i++, j++) {

        if (dentry->name[i] != PLB_GET_CHAR(j))

            return 0;

    }

    if (i != namelen)

        return 0;

    if (j < last && PLB_GET_CHAR(j) != '/')

        return 0;

    if (j == last)

            return 0;

    return (j - start);

}

void tmpfs_lookup(ipc_callid_t rid, ipc_call_t *request)

{

    unsigned next = IPC_GET_ARG1(*request);

    unsigned last = IPC_GET_ARG2(*request);

    int dev_handle = IPC_GET_ARG3(*request);

    if (last < next)

        last += PLB_SIZE;

    if (!root && !tmpfs_init()) {

        ipc_answer_0(rid, ENOMEM);

        return;

    }

    tmpfs_dentry_t *dtmp = root->child;

    tmpfs_dentry_t *dcur = root;

    bool hit = true;

    if (PLB_GET_CHAR(next) == '/')

        next++;     /* eat slash */

    while (next <= last) {

        unsigned delta;

        hit = false;

        do {

            delta = match_path_component(dtmp, next, last);

            if (!delta) {

                dtmp = dtmp->sibling;

            } else {

                hit = true;

                next += delta;

                next++;     /* eat slash */

                dcur = dtmp;

                dtmp = dtmp->child;

            }  

        } while (delta == 0 && dtmp);

        if (!hit) {

            ipc_answer_3(rid, ENOENT, tmpfs_reg.fs_handle,

                dev_handle, dcur->index);

            return;

        }

    }

    ipc_answer_4(rid, EOK, tmpfs_reg.fs_handle, dev_handle, dcur->index,

        dcur->size);

}

void tmpfs_read(ipc_callid_t rid, ipc_call_t *request)

{

    int dev_handle = IPC_GET_ARG1(*request);

    unsigned long index = IPC_GET_ARG2(*request);

    off_t pos = IPC_GET_ARG3(*request);

    /*

     * Lookup the respective dentry.

     */

    link_t *hlp;

    hlp = hash_table_find(&dentries, &index);

    if (!hlp) {

        ipc_answer_0(rid, ENOENT);

        return;

    }

    tmpfs_dentry_t *dentry = hash_table_get_instance(hlp, tmpfs_dentry_t,

        dh_link);

    /*

     * Receive the read request.

     */

    ipc_callid_t callid;

    size_t len;

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

        ipc_answer_0(callid, EINVAL);  

        ipc_answer_0(rid, EINVAL);

        return;

    }

    size_t bytes;

    if (dentry->type == TMPFS_FILE) {

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

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

            bytes);

    } else {

        int i;

        tmpfs_dentry_t *cur = dentry->child;

        assert(dentry->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, cur = dentry->child; i < pos && cur; i++,

            cur = cur->sibling)

            ;

        if (!cur) {

            ipc_answer_0(callid, ENOENT);

            ipc_answer_1(rid, ENOENT, 0);

            return;

        }

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

            strlen(cur->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)

{

    int dev_handle = IPC_GET_ARG1(*request);

    unsigned long index = IPC_GET_ARG2(*request);

    off_t pos = IPC_GET_ARG3(*request);

    /*

     * Lookup the respective dentry.

     */

    link_t *hlp;

    hlp = hash_table_find(&dentries, &index);

    if (!hlp) {

        ipc_answer_0(rid, ENOENT);

        return;

    }

    tmpfs_dentry_t *dentry = hash_table_get_instance(hlp, tmpfs_dentry_t,

        dh_link);

    /*

     * Receive the write request.

     */

    ipc_callid_t callid;

    size_t len;

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

        ipc_answer_0(callid, EINVAL);  

        ipc_answer_0(rid, EINVAL);

        return;

    }

    /*

     * Check whether the file needs to grow.

     */

    if (pos + len <= dentry->size) {

        /* The file size is not changing. */

        (void) ipc_data_write_finalize(callid, dentry->data + pos, len);

        ipc_answer_1(rid, EOK, len);

        return;

    }

    size_t delta = (pos + len) - dentry->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(dentry->data, dentry->size + delta);

    if (!newdata) {

        ipc_answer_0(callid, ENOMEM);

        ipc_answer_1(rid, EOK, 0);

        return;

    }

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

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

    dentry->size += delta;

    dentry->data = newdata;

    (void) ipc_data_write_finalize(callid, dentry->data + pos, len);

    ipc_answer_2(rid, EOK, len, dentry->size);

}

void tmpfs_truncate(ipc_callid_t rid, ipc_call_t *request)

{

    int dev_handle = IPC_GET_ARG1(*request);

    unsigned long index = IPC_GET_ARG2(*request);

    size_t size = IPC_GET_ARG3(*request);

    /*

     * Lookup the respective dentry.

     */

    link_t *hlp;

    hlp = hash_table_find(&dentries, &index);

    if (!hlp) {

        ipc_answer_0(rid, ENOENT);

        return;

    }

    tmpfs_dentry_t *dentry = hash_table_get_instance(hlp, tmpfs_dentry_t,

        dh_link);

    if (size == dentry->size) {

        ipc_answer_0(rid, EOK);

        return;

    }

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

    if (!newdata) {

        ipc_answer_0(rid, ENOMEM);

        return;

    }

    if (size > dentry->size) {

        size_t delta = size - dentry->size;

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

    }

    dentry->size = size;

    dentry->data = newdata;

    ipc_answer_0(rid, EOK);

}

/**

 * @}

 */