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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

#define TMPFS_GET_INDEX(x)	(((tmpfs_dentry_t *)(x))->index)

#define TMPFS_GET_LNKCNT(x)	1

/* Forward declarations of static functions. */

static void *create_node(int);

static bool link_node(void *, void *, const char *);

static int unlink_node(void *);

static void destroy_node(void *);

/** 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 *) create_node(L_DIRECTORY);

	return root != NULL;

}

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

 *

 * @param nodep		Node to compare the path component with.

 * @param component	Array of characters holding component name.

 *

 * @return		True on match, false otherwise.

 */

static bool match_component(void *nodep, const char *component)

{

	tmpfs_dentry_t *dentry = (tmpfs_dentry_t *) nodep;

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

}

void *create_node(int lflag)

{

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

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

	if (!node)

		return NULL;

	tmpfs_dentry_initialize(node);

	node->index = tmpfs_next_index++;

	if (lflag & L_DIRECTORY) 

		node->type = TMPFS_DIRECTORY;

	else 

		node->type = TMPFS_FILE;

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

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

	return (void *) node;

}

bool link_node(void *prnt, void *chld, const char *nm)

{

	tmpfs_dentry_t *parentp = (tmpfs_dentry_t *) prnt;

	tmpfs_dentry_t *childp = (tmpfs_dentry_t *) chld;

	assert(parentp->type == TMPFS_DIRECTORY);

	size_t len = strlen(nm);

	char *name = malloc(len + 1);

	if (!name)

		return false;

	strcpy(name, nm);

	childp->name = name;

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

	if (parentp->child) {

		tmpfs_dentry_t *tmp = parentp->child;

		while (tmp->sibling)

			tmp = tmp->sibling;

		tmp->sibling = childp;

	} else {

		parentp->child = childp;

	}

	childp->parent = parentp;

	return true;

}

int unlink_node(void *nodeptr)

{

	tmpfs_dentry_t *dentry = (tmpfs_dentry_t *)nodeptr;

	if (dentry->child)

		return ENOTEMPTY;

	if (!dentry->parent)

		return EBUSY;

	if (dentry->parent->child == dentry) {

		dentry->parent->child = dentry->sibling;

	} else {

		/* TODO: consider doubly linked list for organizing siblings. */

		tmpfs_dentry_t *tmp = dentry->parent->child;

		while (tmp->sibling != dentry)

			tmp = tmp->sibling;

		tmp->sibling = dentry->sibling;

	}

	dentry->sibling = NULL;

	dentry->parent = NULL;

	free(dentry->name);

	dentry->name = NULL;

	return EOK;

}

void destroy_node(void *nodep)

{

	tmpfs_dentry_t *dentry = (tmpfs_dentry_t *) nodep;

	assert(!dentry->child);

	assert(!dentry->sibling);

	unsigned long index = dentry->index;

	hash_table_remove(&dentries, &index, 1);

	if (dentry->type == TMPFS_FILE)

		free(dentry->data);

	free(dentry);

}

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;

				} 

				void *nodep = create_node(lflag);

				if (nodep) {

					if (!link_node(dcur, nodep,

					    component)) {

						destroy_node(nodep);

						ipc_answer_0(rid, ENOSPC);

					} else {

						ipc_answer_5(rid, EOK,

						    tmpfs_reg.fs_handle,

						    dev_handle,

						    TMPFS_GET_INDEX(nodep), 0,

						    TMPFS_GET_LNKCNT(nodep));

					}

				} 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;

			void *nodep = create_node(lflag);

			if (nodep) {

				if (!link_node(dcur, nodep, component)) {

					destroy_node(nodep);

					ipc_answer_0(rid, ENOSPC);

				} else {

					ipc_answer_5(rid, EOK,

					    tmpfs_reg.fs_handle,

					    dev_handle, TMPFS_GET_INDEX(nodep),

					    0, TMPFS_GET_LNKCNT(nodep));

				}

			} else {

				ipc_answer_0(rid, ENOSPC);

			}

			return;

		}

		ipc_answer_0(rid, ENOENT);

		return;

	}

	/* handle hit */

	if (lflag & L_DESTROY) {

		unsigned old_lnkcnt = TMPFS_GET_LNKCNT(dcur);

		int res = unlink_node(dcur);

		ipc_answer_5(rid, (ipcarg_t)res, tmpfs_reg.fs_handle,

		    dev_handle, dcur->index, dcur->size, old_lnkcnt);

		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_5(rid, EOK, tmpfs_reg.fs_handle, dev_handle, dcur->index,

	    dcur->size, TMPFS_GET_LNKCNT(dcur));

}

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;

		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);

}

void tmpfs_destroy(ipc_callid_t rid, ipc_call_t *request)

{

	int dev_handle = IPC_GET_ARG1(*request);

	unsigned long index = IPC_GET_ARG2(*request);

	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);

	destroy_node(dentry);

	ipc_answer_0(rid, EOK);

}

/**

 * @}

 */