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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 <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_3(rid, EOK, tmpfs_reg.fs_handle, dev_handle, dcur->index);

}

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

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

	/*

	 * 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(dentry->data + dentry->size, 0, delta);

	dentry->size += delta;

	dentry->data = newdata;

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

	ipc_answer_1(rid, EOK, len);

}

/**

 * @}

 */