/*
 *  linux/fs/read_write.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 */

#include <linux/types.h>
#include <linux/errno.h>
#include <linux/stat.h>
#include <linux/kernel.h>
#include <linux/sched.h>

#include <asm/segment.h>

/*
 * Count is now a supported feature, but currently only the ext2fs
 * uses it.  A count value of 1 is supported for compatibility with
 * earlier libraries, but larger values are supported: count should
 * indicate the total buffer space available for filling with dirents.
 * The d_off entry in the dirents will then indicate the offset from
 * each dirent to the next, and the return value will indicate the
 * number of bytes written.  All dirents will be written at
 * word-aligned addresses.  [sct Oct 1994]
 */
asmlinkage int sys_readdir(unsigned int fd, struct dirent * dirent, unsigned int count)
{
	int error;
	struct file * file;
	struct inode * inode;

	if (fd >= NR_OPEN || !(file = current->files->fd[fd]) ||
	    !(inode = file->f_inode))
		return -EBADF;
	error = -ENOTDIR;
	if (file->f_op && file->f_op->readdir) {
		int size = count;
		if (count == 1)
			size = sizeof(*dirent);
		error = verify_area(VERIFY_WRITE, dirent, size);
		if (!error)
			error = file->f_op->readdir(inode,file,dirent,count);
	}
	return error;
}

asmlinkage int sys_lseek(unsigned int fd, off_t offset, unsigned int origin)
{
	struct file * file;
	int tmp = -1;

	if (fd >= NR_OPEN || !(file=current->files->fd[fd]) || !(file->f_inode))
		return -EBADF;
	if (origin > 2)
		return -EINVAL;
	if (file->f_op && file->f_op->lseek)
		return file->f_op->lseek(file->f_inode,file,offset,origin);

/* this is the default handler if no lseek handler is present */
	switch (origin) {
		case 0:
			tmp = offset;
			break;
		case 1:
			tmp = file->f_pos + offset;
			break;
		case 2:
			if (!file->f_inode)
				return -EINVAL;
			tmp = file->f_inode->i_size + offset;
			break;
	}
	if (tmp < 0)
		return -EINVAL;
	if (tmp != file->f_pos) {
		file->f_pos = tmp;
		file->f_reada = 0;
		file->f_version = ++event;
	}
	return file->f_pos;
}

asmlinkage int sys_llseek(unsigned int fd, unsigned long offset_high,
			  unsigned long offset_low, loff_t * result,
			  unsigned int origin)
{
	struct file * file;
	loff_t tmp = -1;
	loff_t offset;
	int err;

	if (fd >= NR_OPEN || !(file=current->files->fd[fd]) || !(file->f_inode))
		return -EBADF;
	if (origin > 2)
		return -EINVAL;
	if ((err = verify_area(VERIFY_WRITE, result, sizeof(loff_t))))
		return err;
	offset = (loff_t) (((unsigned long long) offset_high << 32) | offset_low);
/* there is no fs specific llseek handler */
	switch (origin) {
		case 0:
			tmp = offset;
			break;
		case 1:
			tmp = file->f_pos + offset;
			break;
		case 2:
			if (!file->f_inode)
				return -EINVAL;
			tmp = file->f_inode->i_size + offset;
			break;
	}
	if (tmp < 0)
		return -EINVAL;
	file->f_pos = tmp;
	file->f_reada = 0;
	file->f_version = ++event;
	memcpy_tofs(result, &file->f_pos, sizeof(loff_t));
	return 0;
}

asmlinkage int sys_read(unsigned int fd,char * buf,unsigned int count)
{
	int error;
	struct file * file;
	struct inode * inode;

	if (fd>=NR_OPEN || !(file=current->files->fd[fd]) || !(inode=file->f_inode))
		return -EBADF;
	if (!(file->f_mode & 1))
		return -EBADF;
	if (!file->f_op || !file->f_op->read)
		return -EINVAL;
	if (!count)
		return 0;
	error = verify_area(VERIFY_WRITE,buf,count);
	if (error)
		return error;
	return file->f_op->read(inode,file,buf,count);
}

asmlinkage int sys_write(unsigned int fd,char * buf,unsigned int count)
{
	int error;
	struct file * file;
	struct inode * inode;
	int written;
	
	if (fd>=NR_OPEN || !(file=current->files->fd[fd]) || !(inode=file->f_inode))
		return -EBADF;
	if (!(file->f_mode & 2))
		return -EBADF;
	if (!file->f_op || !file->f_op->write)
		return -EINVAL;
	if (!count)
		return 0;
	error = verify_area(VERIFY_READ,buf,count);
	if (error)
		return error;
	written = file->f_op->write(inode,file,buf,count);
	/*
	 * If data has been written to the file, remove the setuid and
	 * the setgid bits
	 */
	if (written > 0 && !suser() && (inode->i_mode & (S_ISUID | S_ISGID))) {
		struct iattr newattrs;
		newattrs.ia_mode = inode->i_mode & ~(S_ISUID | S_ISGID);
		newattrs.ia_valid = ATTR_MODE;
		notify_change(inode, &newattrs);
	}
	return written;
}