/*
 *  linux/fs/file_dev.c
 *
 *  (C) 1991  Linus Torvalds
 */

#include <errno.h>
#include <fcntl.h>

#include <linux/sched.h>
#include <linux/kernel.h>
#include <asm/segment.h>
#include <sys/types.h>
#include <new.h>

#define MIN(a,b) (((a)<(b))?(a):(b))
#define MAX(a,b) (((a)>(b))?(a):(b))
#define PATH_MAX 255

int file_read(struct m_inode * inode, struct file * filp, char *  buf, int count)
{
	int left,chars,nr;
	struct buffer_head * bh;

	if ((left=count)<=0)
		return 0;
	while (left) {
		if (nr = bmap(inode,(filp->f_pos)/BLOCK_SIZE)) {
			if (!(bh=bread(inode->i_dev,nr)))
				break;
		} else
			bh = NULL;
		nr = filp->f_pos % BLOCK_SIZE;
		chars = MIN( BLOCK_SIZE-nr , left );
		filp->f_pos += chars;
		left -= chars;
		if (bh) {
			char * p = nr + bh->b_data;
			while (chars-->0)
				put_fs_byte(*(p++),buf++);
			brelse(bh);
		} else {
			while (chars-->0)
				put_fs_byte(0,buf++);
		}
	}
	inode->i_atime = CURRENT_TIME;
	return (count-left)?(count-left):-ERROR;
}

int file_write(struct m_inode * inode, struct file * filp, char * buf, int count)
{
	off_t pos;
	int block,c;
	struct buffer_head * bh;
	char * p;
	int i=0;

/*
 * ok, append may not work when many processes are writing at the same time
 * but so what. That way leads to madness anyway.
 */
	if (filp->f_flags & O_APPEND)
		pos = inode->i_size;
	else
		pos = filp->f_pos;
	while (i<count) {
		if (!(block = create_block(inode,pos/BLOCK_SIZE)))
			break;
		if (!(bh=bread(inode->i_dev,block)))
			break;
		c = pos % BLOCK_SIZE;
		p = c + bh->b_data;
		bh->b_dirt = 1;
		c = BLOCK_SIZE-c;
		if (c > count-i) c = count-i;
		pos += c;
		if (pos > inode->i_size) {
			inode->i_size = pos;
			inode->i_dirt = 1;
		}
		i += c;
		while (c-->0)
			*(p++) = get_fs_byte(buf++);
		brelse(bh);
	}
	inode->i_mtime = CURRENT_TIME;
	if (!(filp->f_flags & O_APPEND)) {
		filp->f_pos = pos;
		inode->i_ctime = CURRENT_TIME;
	}
	return (i?i:-1);
}

int sys_getdents(unsigned int fd, struct linux_dirent *d, unsigned int count)
{
    struct linux_dirent tmp;
    struct file  * file;
	struct m_inode * inode;
    struct buffer_head * block;
    struct dir_entry * ptr;
    char * buf;
	int bpos; 
    int dpos;
    int ld_size;
    int i;

    ld_size = sizeof(struct linux_dirent);          /* size of linux_dirent */
    file = current->filp[fd];                       /* opened file */

    if (fd >= NR_OPEN)
		return -EINVAL;
	if (!count)
		return -1;
    if (!file)
        return ENOTDIR;

    inode = file->f_inode;
    block = bread(inode->i_dev,inode->i_zone[0]);

    /* count:   size of linux_dirent[], target 
     * dd_size: size of dir_entry[], block 400?
     */
    for (dpos = 0,bpos = 0;bpos<inode->i_size;bpos += sizeof(struct dir_entry)) {
        if (dpos >= (count-ld_size))
            return 0; /* d full */
        ptr = (struct dir_entry *) (bpos + block->b_data);
        if (!ptr -> inode)
            continue; /* when it 's empty inode, jump it */
        
        tmp.d_ino = ptr -> inode;
		for (i = 0; i < 14; i++) tmp.d_name[i] = ptr -> name[i];
        tmp.d_reclen = sizeof(tmp);
        tmp.d_off = 0;

		buf = &tmp;
        for (i = 0; i < tmp.d_reclen; i++){
            put_fs_byte(*(buf+i),((char*)d)+i+dpos); /* move data from kernel to user */ 
        }
        dpos += tmp.d_reclen;
    }
    return dpos;
}

long sys_mmap(void *start, size_t len, int prot, int flags, 
    int fd, off_t off)
{
	return 0;
}

int sys_munmap(void * start, size_t len)
{
	return 0;
}