/*
 * xhtab.c - Remote access embedded hash table implementation.
 * 
 * Author     Alain Greiner          (2016,2017)
 *
 * Copyright (c) UPMC Sorbonne Universites
 *
 * This file is part of ALMOS-MKH.
 *
 * ALMOS-MKH is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by
 * the Free Software Foundation; version 2.0 of the License.
 *
 * ALMOS-MKH is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with ALMOS-MKH; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include <kernel_config.h>
#include <hal_types.h>
#include <hal_special.h>
#include <hal_remote.h>
#include <xlist.h>
#include <remote_rwlock.h>
#include <string.h>
#include <printk.h>
#include <xhtab.h>
#include <vfs.h>


///////////////////////////////////////////////////////////////////////////////////////////
// Item type specific (static) functions (two functions for each item type).
// - for type <vfs_dentry_t>, identifier is the name field.
///////////////////////////////////////////////////////////////////////////////////////////

///////////////////////////////////////////////////////////////////////////////////////////
// These static functions compute the hash index from the key.
///////////////////////////////////////////////////////////////////////////////////////////
// @ key      : local pointer on key.
// @ return the index value, from 0 to (HASHTAB_SIZE - 1)
///////////////////////////////////////////////////////////////////////////////////////////

/////////////////////////////////////////
uint32_t xhtab_dentry_index( void * key )
{
	char     * name  = key;
	uint32_t   index = 0;
	while( *name )
    {
        index = index + (*(name++) ^ index);
    }
	return index % HASHTAB_SIZE;
} 

////////////////////////////////////////////////////////////////////////////////////////////
// These static function are used by xhtab_lookup(), xhtab_insert(), xhtab_remove().
// They scan one sub-list identified by  <index> to find an item  identified by <key>.
// The sub-list is not modified, but the readlock must have been taken by the caller.
////////////////////////////////////////////////////////////////////////////////////////////
// @ xhtab_xp  : extended pointer on hash table.
// @ index     : index of sub-list to be scanned.
// @ key       : local pointer on item identifier.
// return an extended pointer on item if found / return XPTR_NULL if not found.
////////////////////////////////////////////////////////////////////////////////////////////

////////////////////////////////////////////////////
static xptr_t xhtab_dentry_scan( xptr_t    xhtab_xp,
                                 uint32_t  index,
                                 void    * key )
{
    xptr_t    xlist_xp;                                 // xlist_entry_t (iterator)
    xhtab_t * xhtab_ptr;                                // hash table local pointer
    cxy_t     xhtab_cxy;                                // hash table cluster
    char      local_name[CONFIG_VFS_MAX_NAME_LENGTH];   // local copy of dentry name

    // get hash table cluster and local pointer
    xhtab_cxy = GET_CXY( xhtab_xp );
    xhtab_ptr = (xhtab_t *)GET_PTR( xhtab_xp );

    // scan sub-list[index]
    XLIST_FOREACH( XPTR( xhtab_cxy , &xhtab_ptr->roots[index] ) , xlist_xp )
    {
        // get extended pointer on dentry containing the xlist_entry_t
	    xptr_t dentry_xp = XLIST_ELEMENT( xlist_xp , vfs_dentry_t , xlist );

        // get dentry cluster and local pointer 
        cxy_t          dentry_cxy = GET_CXY( dentry_xp );
        vfs_dentry_t * dentry_ptr = (vfs_dentry_t *)GET_PTR( dentry_xp );
    
        // make a local copy of dentry name
        hal_remote_memcpy( XPTR( local_cxy  , local_name ) ,
                           XPTR( dentry_cxy , dentry_ptr->name ),
                           CONFIG_VFS_MAX_NAME_LENGTH  );

        // check matching 
        if( strcmp( local_name , (char *)key ) == 0 ) return dentry_xp; 
    }

    // No matching item found
    return XPTR_NULL;
}

////////////////////////////////////////////////////////////////////////////////////////
//         Generic access functions
////////////////////////////////////////////////////////////////////////////////////////

//////////////////////////////////////////
void xhtab_init( xhtab_t          * xhtab,
                 xhtab_item_type_t  type )
{
	uint32_t i;

    // initialize readlock
    remote_rwlock_init( XPTR( local_cxy , &xhtab->lock) );

    xhtab->items  = 0;

    if( type == XHTAB_DENTRY_TYPE )
    {
        xhtab->scan  = &xhtab_dentry_scan;
        xhtab->index = &xhtab_dentry_index;
    }
    else
    {
        printk("\n[PANIC] in %s : illegal item type\n", __FUNCTION__ );
        hal_core_sleep();
    }

	for( i=0 ; i < HASHTAB_SIZE ; i++ )
    {
		xlist_root_init( XPTR( local_cxy , &xhtab->roots[i] ) );
    }  
}

///////////////////////////////////////
error_t xhtab_insert( xptr_t   xhtab_xp,
                      void   * key,
                      xptr_t   xlist_xp )
{
    // get xhtab cluster and local pointer 
    cxy_t     xhtab_cxy = GET_CXY( xhtab_xp );
    xhtab_t * xhtab_ptr = (xhtab_t *)GET_PTR( xhtab_xp );

    // compute index from key
	uint32_t index = xhtab_ptr->index( key );

    // take the lock protecting hash table
    remote_rwlock_wr_lock( XPTR( xhtab_cxy , &xhtab_ptr->lock ) );

    // search a matching item 
    xptr_t item_xp = xhtab_ptr->scan( xhtab_xp , index , key );

    if( item_xp != XPTR_NULL )    // error if found
    {
        // release the lock protecting hash table
        remote_rwlock_wr_unlock( XPTR( xhtab_cxy , &xhtab_ptr->lock ) );

        return EINVAL;
    }
    else                          // insert item if not found
    {
        // register item in hash table
	    xlist_add_last( XPTR( xhtab_cxy , &xhtab_ptr->roots[index] ) , xlist_xp );

        // update number of registered items
        hal_remote_atomic_add( XPTR( xhtab_cxy , &xhtab_ptr->items ) , 1 );

        // release the lock protecting hash table
        remote_rwlock_wr_unlock( XPTR( xhtab_cxy , &xhtab_ptr->lock ) );

        return 0;
    }
}  // end xhtab_insert()

/////////////////////////////////////
error_t xhtab_remove( xptr_t   xhtab_xp,
                      void   * key,
                      xptr_t   xlist_entry_xp )
{
    // get xhtab cluster and local pointer 
    cxy_t     xhtab_cxy = GET_CXY( xhtab_xp );
    xhtab_t * xhtab_ptr = (xhtab_t *)GET_PTR( xhtab_xp );

    // compute index from key
	uint32_t index = xhtab_ptr->index( key );

    // take the lock protecting hash table
    remote_rwlock_wr_lock( XPTR( xhtab_cxy , &xhtab_ptr->lock ) );

    // get extended pointer on item to remove
    xptr_t item_xp = xhtab_ptr->scan( xhtab_xp , index , key );

    if( item_xp == XPTR_NULL )    // error if not found
    {
        // release the lock protecting hash table
        remote_rwlock_wr_unlock( XPTR( xhtab_cxy , &xhtab_ptr->lock ) );

        return EINVAL;
    }
    else                          // remove item if found
    {
        // remove item from hash table <=> unlink xlist_entry_t
        xlist_unlink( xlist_entry_xp );

        // update number of registered items
        hal_remote_atomic_add( XPTR( xhtab_cxy , &xhtab_ptr->items ) , -1 );

        // release the lock protecting hash table
        remote_rwlock_wr_unlock( XPTR( xhtab_cxy , &xhtab_ptr->lock ) );

        return 0;
    }
}  // end xhtab_remove()

/////////////////////////////////////////
xptr_t  xhtab_lookup( xptr_t    xhtab_xp,
                      void    * key )
{
    xptr_t  item_xp;

    // get xhtab cluster and local pointer 
    cxy_t     xhtab_cxy = GET_CXY( xhtab_xp );
    xhtab_t * xhtab_ptr = (xhtab_t *)GET_PTR( xhtab_xp );

    // compute index from key
	uint32_t index = xhtab_ptr->index( key );

    // take the lock protecting hash table
    remote_rwlock_rd_lock( XPTR( xhtab_cxy , &xhtab_ptr->lock ) );

    // scan sub-list
    item_xp = xhtab_ptr->scan( xhtab_xp , index , key );

    // release the lock protecting hash table
    remote_rwlock_rd_unlock( XPTR( xhtab_cxy , &xhtab_ptr->lock ) );

    return item_xp;

}  // end xhtab_lookup()