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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 <dirent.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);

    return true;

}

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

 *

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

 * @param component Array of characters holding component name.

 *

 * @return      True on match, false otherwise.

 */

static bool match_component(tmpfs_dentry_t *dentry, const char *component)

{

    return !strcmp(dentry->name, component);

}

static unsigned long create_node(tmpfs_dentry_t *dentry,

    const char *component, int lflag)

{

    assert(dentry->type == TMPFS_DIRECTORY);

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

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

    if (!node)

        return 0;

    size_t len = strlen(component);

    char *name = malloc(len + 1);

    if (!name) {

        free(node);

        return 0;

    }

    strcpy(name, component);

    tmpfs_dentry_initialize(node);

    node->index = tmpfs_next_index++;

    node->name = name;

    node->parent = dentry;

    if (lflag & L_DIRECTORY)

        node->type = TMPFS_DIRECTORY;

    else

        node->type = TMPFS_FILE;

    /* Insert the new node into the namespace. */

    if (dentry->child) {

        tmpfs_dentry_t *tmp = dentry->child;

        while (tmp->sibling)

            tmp = tmp->sibling;

        tmp->sibling = node;

    } else {

        dentry->child = node;

    }

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

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

    return node->index;

}

static int destroy_component(tmpfs_dentry_t *dentry)

{

    return EPERM;

}

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);

    int lflag = IPC_GET_ARG4(*request);

    if (last < next)

        last += PLB_SIZE;

    /*

     * Initialize TMPFS.

     */

    if (!root && !tmpfs_init()) {

        ipc_answer_0(rid, ENOMEM);

        return;

    }

    tmpfs_dentry_t *dtmp = root->child;

    tmpfs_dentry_t *dcur = root;

    if (PLB_GET_CHAR(next) == '/')

        next++;     /* eat slash */

    char component[NAME_MAX + 1];

    int len = 0;

    while (dtmp && next <= last) {

        /* collect the component */

        if (PLB_GET_CHAR(next) != '/') {

            if (len + 1 == NAME_MAX) {

                /* comopnent length overflow */

                ipc_answer_0(rid, ENAMETOOLONG);

                return;

            }

            component[len++] = PLB_GET_CHAR(next);

            next++; /* process next character */

            if (next <= last)

                continue;

        }

        assert(len);

        component[len] = '\0';

        next++;     /* eat slash */

        len = 0;

        /* match the component */

        while (dtmp && !match_component(dtmp, component))

            dtmp = dtmp->sibling;

        /* handle miss: match amongst siblings */

        if (!dtmp) {

            if ((next > last) && (lflag & L_CREATE)) {

                /* no components left and L_CREATE specified */

                if (dcur->type != TMPFS_DIRECTORY) {

                    ipc_answer_0(rid, ENOTDIR);

                    return;

                }

                unsigned long index = create_node(dcur,

                    component, lflag);

                if (index > 0) {

                    ipc_answer_4(rid, EOK,

                        tmpfs_reg.fs_handle, dev_handle,

                        index, 0);

                } else {

                    ipc_answer_0(rid, ENOSPC);

                }

                return;

            }

            ipc_answer_0(rid, ENOENT);

            return;

        }

        /* descend one level */

        dcur = dtmp;

        dtmp = dtmp->child;

    }

    /* handle miss: excessive components */

    if (!dtmp && next <= last) {

        if (lflag & L_CREATE) {

            if (dcur->type != TMPFS_DIRECTORY) {

                ipc_answer_0(rid, ENOTDIR);

                return;

            }

            /* collect next component */

            while (next <= last) {

                if (PLB_GET_CHAR(next) == '/') {

                    /* more than one component */

                    ipc_answer_0(rid, ENOENT);

                    return;

                }

                if (len + 1 == NAME_MAX) {

                    /* component length overflow */

                    ipc_answer_0(rid, ENAMETOOLONG);

                    return;

                }

                component[len++] = PLB_GET_CHAR(next);

                next++; /* process next character */

            }

            assert(len);

            component[len] = '\0';

            len = 0;

            unsigned long index;

            index = create_node(dcur, component, lflag);

            if (index) {

                ipc_answer_4(rid, EOK, tmpfs_reg.fs_handle,

                    dev_handle, index, 0);

            } else {

                ipc_answer_0(rid, ENOSPC);

            }

            return;

        }

        ipc_answer_0(rid, ENOENT);

        return;

    }

    /* handle hit */

    if (lflag & L_DESTROY) {

        int res = destroy_component(dcur);

        ipc_answer_0(rid, res);

        return;

    }

    if ((lflag & (L_CREATE | L_EXCLUSIVE)) == (L_CREATE | L_EXCLUSIVE)) {

        ipc_answer_0(rid, EEXIST);

        return;

    }

    if ((lflag & L_FILE) && (dcur->type != TMPFS_FILE)) {

        ipc_answer_0(rid, EISDIR);

        return;

    }

    if ((lflag & L_DIRECTORY) && (dcur->type != TMPFS_DIRECTORY)) {

        ipc_answer_0(rid, ENOTDIR);

        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_2(rid, EOK, len, dentry->size);

        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_2(rid, EOK, 0, dentry->size);

        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);

}

/**

 * @}

 */