##include "../param.h"#include "../inode.h"#include "../user.h"#include "../systm.h"#include "../buf.h"/* * Convert a pathname into a pointer to * an inode. Note that the inode is locked. * * func = function called to get next char of name *	&uchar if name is in user space *	&schar if name is in system space * flag = 0 if name is sought *	1 if name is to be created *	2 if name is to be deleted */namei(func, flag)int (*func)();{	register struct inode *dp;	register c;	register char *cp;	int eo, *bp;	/*	 * If name starts with '/' start from	 * root; otherwise start from current dir.	 */	dp = u.u_cdir;	if((c=(*func)()) == '/')		dp = rootdir;	iget(dp->i_dev, dp->i_number);	while(c == '/')		c = (*func)();	if(c == '\0' && flag != 0) {		u.u_error = ENOENT;		goto out;	}cloop:	/*	 * Here dp contains pointer	 * to last component matched.	 */	if(u.u_error)		goto out;	if(c == '\0')		return(dp);	/*	 * If there is another component,	 * dp must be a directory and	 * must have x permission.	 */	if((dp->i_mode&IFMT) != IFDIR) {		u.u_error = ENOTDIR;		goto out;	}	if(access(dp, IEXEC))		goto out;	/*	 * Gather up name into	 * users' dir buffer.	 */	cp = &u.u_dbuf[0];	while(c!='/' && c!='\0' && u.u_error==0) {		if(cp < &u.u_dbuf[DIRSIZ])			*cp++ = c;		c = (*func)();	}	while(cp < &u.u_dbuf[DIRSIZ])		*cp++ = '\0';	while(c == '/')		c = (*func)();	if(u.u_error)		goto out;	/*	 * Set up to search a directory.	 */	u.u_offset[1] = 0;	u.u_offset[0] = 0;	u.u_segflg = 1;	eo = 0;	u.u_count = ldiv(dp->i_size1, DIRSIZ+2);	bp = NULL;eloop:	/*	 * If at the end of the directory,	 * the search failed. Report what	 * is appropriate as per flag.	 */	if(u.u_count == 0) {		if(bp != NULL)			brelse(bp);		if(flag==1 && c=='\0') {			if(access(dp, IWRITE))				goto out;			u.u_pdir = dp;			if(eo)				u.u_offset[1] = eo-DIRSIZ-2; else				dp->i_flag =| IUPD;			return(NULL);		}		u.u_error = ENOENT;		goto out;	}	/*	 * If offset is on a block boundary,	 * read the next directory block.	 * Release previous if it exists.	 */	if((u.u_offset[1]&0777) == 0) {		if(bp != NULL)			brelse(bp);		bp = bread(dp->i_dev,			bmap(dp, ldiv(u.u_offset[1], 512)));	}	/*	 * Note first empty directory slot	 * in eo for possible creat.	 * String compare the directory entry	 * and the current component.	 * If they do not match, go back to eloop.	 */	bcopy(bp->b_addr+(u.u_offset[1]&0777), &u.u_dent, (DIRSIZ+2)/2);	u.u_offset[1] =+ DIRSIZ+2;	u.u_count--;	if(u.u_dent.u_ino == 0) {		if(eo == 0)			eo = u.u_offset[1];		goto eloop;	}	for(cp = &u.u_dbuf[0]; cp < &u.u_dbuf[DIRSIZ]; cp++)		if(*cp != cp[u.u_dent.u_name - u.u_dbuf])			goto eloop;	/*	 * Here a component matched in a directory.	 * If there is more pathname, go back to	 * cloop, otherwise return.	 */	if(bp != NULL)		brelse(bp);	if(flag==2 && c=='\0') {		if(access(dp, IWRITE))			goto out;		return(dp);	}	bp = dp->i_dev;	iput(dp);	dp = iget(bp, u.u_dent.u_ino);	if(dp == NULL)		return(NULL);	goto cloop;out:	iput(dp);	return(NULL);}/* * Return the next character from the * kernel string pointed at by dirp. */schar(){	return(*u.u_dirp++ & 0377);}/* * Return the next character from the * user string pointed at by dirp. */uchar(){	register c;	c = fubyte(u.u_dirp++);	if(c == -1)		u.u_error = EFAULT;	return(c);}