/*
 * sys_readdir.c - Copy one entry from an open VFS directory to an user buffer.
 *
 * Author    Alain Greiner (2016,2017,2018,2019,2020)
 *
 * 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_kernel_types.h>
#include <hal_uspace.h>
#include <hal_vmm.h>
#include <errno.h>
#include <thread.h>
#include <printk.h>
#include <vfs.h>
#include <process.h>
#include <user_dir.h>
#include <syscalls.h>
#include <shared_syscalls.h>

///////////////////////////////////////
int sys_readdir( DIR            * dirp,
                 struct dirent ** buffer )
{
    error_t         error;
    vseg_t        * vseg;               // for user space checking of buffer
    xptr_t          dir_xp;             // extended pointer on user_dir structure
    user_dir_t    * dir_ptr;            // local pointer on user_dir structure
    cxy_t           dir_cxy;            // user_dir stucture cluster identifier
    struct dirent * direntp;            // dirent pointer in user space  
    uint32_t        entries;            // total number of dirent entries
    uint32_t        current;            // current dirent index

	thread_t  * this    = CURRENT_THREAD;  // client thread
	process_t * process = this->process;   // client process

#if (DEBUG_SYS_READDIR || DEBUG_SYSCALLS_ERROR || CONFIG_INSTRUMENTATION_SYSCALLS)
uint64_t     tm_start = hal_get_cycles();
#endif

#if DEBUG_SYS_READDIR
if( DEBUG_SYS_READDIR < tm_start )
printk("\n[%s] thread[%x,%x] enter / dirp %x / cycle %d\n",
__FUNCTION__, process->pid, this->trdid, dirp, (uint32_t)tm_start );
#endif
 
    // check dirent buffer in user space
    error = vmm_get_vseg( process , (intptr_t)buffer, &vseg );

	if( error )
	{

#if DEBUG_SYSCALLS_ERROR
if( DEBUG_SYSCALLS_ERROR < (uint32_t)tm_start )
printk("\n[ERROR] in %s : thread[%x,%x] / dirent user buffer %x unmapped\n",
__FUNCTION__ , process->pid , this->trdid, buffer );
#endif
		this->errno = EINVAL;
		return -1;
	}	

    // get pointers on user_dir structure from dirp
    dir_xp  = user_dir_from_ident( (intptr_t)dirp );
    dir_ptr = GET_PTR( dir_xp );
    dir_cxy = GET_CXY( dir_xp );

    if( dir_xp == XPTR_NULL )
	{

#if DEBUG_SYSCALLS_ERROR
if( DEBUG_SYSCALLS_ERROR < (uint32_t)tm_start )
printk("\n[ERROR] in %s : thread[%x,%x] / dirp %x not registered\n",
__FUNCTION__ , process->pid , this->trdid, dirp );
#endif
		this->errno = EBADF;
		return -1;
	}	

    // get "current" and "entries_nr" values from user_dir_t structure
    current = hal_remote_l32( XPTR( dir_cxy , &dir_ptr->current ) );
    entries = hal_remote_l32( XPTR( dir_cxy , &dir_ptr->entries ) );

    // check "current" index
    if( current >= entries )
    {
        this->errno = 0;
        return -1;
    }

    // compute dirent pointer in user space
    direntp = (struct dirent *)dirp + current;

#if (DEBUG_SYS_READDIR & 1)
if( DEBUG_SYS_READDIR < (uint32_t)tm_start )
printk("\n[%s] entries = %d / current = %d / direntp = %x\n",
__FUNCTION__, entries, current, direntp );
#endif

    // copy dirent pointer to user buffer 
    hal_copy_to_uspace( buffer,
                        XPTR( local_cxy , &direntp ),
                        sizeof(void *) );

    // update current index in user_dir structure
    hal_remote_atomic_add( XPTR( dir_cxy , &dir_ptr->current ) , 1 );

    hal_fence();

#if (DEBUG_SYS_READDIR || CONFIG_INSTRUMENTATION_SYSCALLS)
uint64_t     tm_end = hal_get_cycles();
#endif

#if DEBUG_SYS_READDIR
if( DEBUG_SYS_READDIR < (uint32_t)tm_end )
printk("\n[%s] thread[%x,%x] exit / cycle %d\n",
__FUNCTION__, process->pid, this->trdid, (uint32_t)tm_end );
#endif
 
#if CONFIG_INSTRUMENTATION_SYSCALLS
hal_atomic_add( &syscalls_cumul_cost[SYS_READDIR] , tm_end - tm_start );
hal_atomic_add( &syscalls_occurences[SYS_READDIR] , 1 );
#endif

	return 0;

}  // end sys_readdir()