/* *  linux/fs/read_write.c * *  (C) 1991  Linus Torvalds */#include <sys/stat.h>#include <errno.h>#include <sys/types.h>#include <linux/kernel.h>#include <linux/sched.h>#include <asm/segment.h>extern int rw_char(int rw,int dev, char * buf, int count, off_t * pos);extern int read_pipe(struct m_inode * inode, char * buf, int count);extern int write_pipe(struct m_inode * inode, char * buf, int count);extern int block_read(int dev, off_t * pos, char * buf, int count);extern int block_write(int dev, off_t * pos, char * buf, int count);extern int file_read(struct m_inode * inode, struct file * filp,		char * buf, int count);extern int file_write(struct m_inode * inode, struct file * filp,		char * buf, int count);int sys_lseek(unsigned int fd,off_t offset, int origin){	struct file * file;	int tmp;	if (fd >= NR_OPEN || !(file=current->filp[fd]) || !(file->f_inode)	   || !IS_SEEKABLE(MAJOR(file->f_inode->i_dev)))		return -EBADF;	if (file->f_inode->i_pipe)		return -ESPIPE;	switch (origin) {		case 0:			if (offset<0) return -EINVAL;			file->f_pos=offset;			break;		case 1:			if (file->f_pos+offset<0) return -EINVAL;			file->f_pos += offset;			break;		case 2:			if ((tmp=file->f_inode->i_size+offset) < 0)				return -EINVAL;			file->f_pos = tmp;			break;		default:			return -EINVAL;	}	return file->f_pos;}int sys_read(unsigned int fd,char * buf,int count){	struct file * file;	struct m_inode * inode;	if (fd>=NR_OPEN || count<0 || !(file=current->filp[fd]))		return -EINVAL;	if (!count)		return 0;	verify_area(buf,count);	inode = file->f_inode;	if (inode->i_pipe)		return (file->f_mode&1)?read_pipe(inode,buf,count):-EIO;	if (S_ISCHR(inode->i_mode))		return rw_char(READ,inode->i_zone[0],buf,count,&file->f_pos);	if (S_ISBLK(inode->i_mode))		return block_read(inode->i_zone[0],&file->f_pos,buf,count);	if (S_ISDIR(inode->i_mode) || S_ISREG(inode->i_mode)) {		if (count+file->f_pos > inode->i_size)			count = inode->i_size - file->f_pos;		if (count<=0)			return 0;		return file_read(inode,file,buf,count);	}	printk("(Read)inode->i_mode=%06o\n\r",inode->i_mode);	return -EINVAL;}int sys_write(unsigned int fd,char * buf,int count){	struct file * file;	struct m_inode * inode;		if (fd>=NR_OPEN || count <0 || !(file=current->filp[fd]))		return -EINVAL;	if (!count)		return 0;	inode=file->f_inode;	if (inode->i_pipe)		return (file->f_mode&2)?write_pipe(inode,buf,count):-EIO;	if (S_ISCHR(inode->i_mode))		return rw_char(WRITE,inode->i_zone[0],buf,count,&file->f_pos);	if (S_ISBLK(inode->i_mode))		return block_write(inode->i_zone[0],&file->f_pos,buf,count);	if (S_ISREG(inode->i_mode))		return file_write(inode,file,buf,count);	printk("(Write)inode->i_mode=%06o\n\r",inode->i_mode);	return -EINVAL;}