#/* */#include "../param.h"#include "../conf.h"#include "../inode.h"#include "../user.h"#include "../buf.h"#include "../systm.h"/* * Bmap defines the structure of file system storage * by returning the physical block number on a device given the * inode and the logical block number in a file. * When convenient, it also leaves the physical * block number of the next block of the file in rablock * for use in read-ahead. */bmap(ip, bn)struct inode *ip;int bn;{	register *bp, *bap, nb;	int *nbp, d, i;	d = ip->i_dev;	if(bn & ~077777) {		u.u_error = EFBIG;		return(0);	}	if((ip->i_mode&ILARG) == 0) {		/*		 * small file algorithm		 */		if((bn & ~7) != 0) {			/*			 * convert small to large			 */			if ((bp = alloc(d)) == NULL)				return(NULL);			bap = bp->b_addr;			for(i=0; i<8; i++) {				*bap++ = ip->i_addr[i];				ip->i_addr[i] = 0;			}			ip->i_addr[0] = bp->b_blkno;			bdwrite(bp);			ip->i_mode =| ILARG;			goto large;		}		nb = ip->i_addr[bn];		if(nb == 0 && (bp = alloc(d)) != NULL) {			bdwrite(bp);			nb = bp->b_blkno;			ip->i_addr[bn] = nb;			ip->i_flag =| IUPD;		}		rablock = 0;		if (bn<7)			rablock = ip->i_addr[bn+1];		return(nb);	}	/*	 * large file algorithm	 */    large:	i = bn>>8;	if(bn & 0174000)		i = 7;	if((nb=ip->i_addr[i]) == 0) {		ip->i_flag =| IUPD;		if ((bp = alloc(d)) == NULL)			return(NULL);		ip->i_addr[i] = bp->b_blkno;	} else		bp = bread(d, nb);	bap = bp->b_addr;	/*	 * "huge" fetch of double indirect block	 */	if(i == 7) {		i = ((bn>>8) & 0377) - 7;		if((nb=bap[i]) == 0) {			if((nbp = alloc(d)) == NULL) {				brelse(bp);				return(NULL);			}			bap[i] = nbp->b_blkno;			bdwrite(bp);		} else {			brelse(bp);			nbp = bread(d, nb);		}		bp = nbp;		bap = bp->b_addr;	}	/*	 * normal indirect fetch	 */	i = bn & 0377;	if((nb=bap[i]) == 0 && (nbp = alloc(d)) != NULL) {		nb = nbp->b_blkno;		bap[i] = nb;		bdwrite(nbp);		bdwrite(bp);	} else		brelse(bp);	rablock = 0;	if(i < 255)		rablock = bap[i+1];	return(nb);}/* * Pass back  c  to the user at his location u_base; * update u_base, u_count, and u_offset.  Return -1 * on the last character of the user's read. * u_base is in the user address space unless u_segflg is set. */passc(c)char c;{	if(u.u_segflg)		*u.u_base = c; else		if(subyte(u.u_base, c) < 0) {			u.u_error = EFAULT;			return(-1);		}	u.u_count--;	if(++u.u_offset[1] == 0)		u.u_offset[0]++;	u.u_base++;	return(u.u_count == 0? -1: 0);}/* * Pick up and return the next character from the user's * write call at location u_base; * update u_base, u_count, and u_offset.  Return -1 * when u_count is exhausted.  u_base is in the user's * address space unless u_segflg is set. */cpass(){	register c;	if(u.u_count == 0)		return(-1);	if(u.u_segflg)		c = *u.u_base; else		if((c=fubyte(u.u_base)) < 0) {			u.u_error = EFAULT;			return(-1);		}	u.u_count--;	if(++u.u_offset[1] == 0)		u.u_offset[0]++;	u.u_base++;	return(c&0377);}/* * Routine which sets a user error; placed in * illegal entries in the bdevsw and cdevsw tables. */nodev(){	u.u_error = ENODEV;}/* * Null routine; placed in insignificant entries * in the bdevsw and cdevsw tables. */nulldev(){}/* * copy count words from from to to. */bcopy(from, to, count)int *from, *to;{	register *a, *b, c;	a = from;	b = to;	c = count;	do		*b++ = *a++;	while(--c);}