457 lines
15 KiB
C
457 lines
15 KiB
C
/* This file contains the procedures that look up path names in the directory
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* system and determine the inode number that goes with a given path name.
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*
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* The entry points into this file are
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* eat_path: the 'main' routine of the path-to-inode conversion mechanism
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* last_dir: find the final directory on a given path
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* advance: parse one component of a path name
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* search_dir: search a directory for a string and return its inode number
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*/
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#include "fs.h"
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#include <string.h>
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#include <minix/callnr.h>
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#include "buf.h"
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#include "file.h"
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#include "fproc.h"
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#include "inode.h"
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#include "super.h"
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PUBLIC char dot1[2] = "."; /* used for search_dir to bypass the access */
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PUBLIC char dot2[3] = ".."; /* permissions for . and .. */
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FORWARD _PROTOTYPE( char *get_name, (char *old_name, char string [NAME_MAX]) );
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/*===========================================================================*
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* eat_path *
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*===========================================================================*/
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PUBLIC struct inode *eat_path(path)
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char *path; /* the path name to be parsed */
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{
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/* Parse the path 'path' and put its inode in the inode table. If not possible,
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* return NIL_INODE as function value and an error code in 'err_code'.
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*/
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register struct inode *ldip, *rip, *old_workdir_ip;
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char string[NAME_MAX]; /* hold 1 path component name here */
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int slink_found;
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int loops = 0; /* count symlink traversals */
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old_workdir_ip = fp->fp_workdir; /* save the current working directory */
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do {
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slink_found = FALSE;
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/* First open the path down to the final directory. */
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if ( (ldip = last_dir(path, string)) == NIL_INODE) {
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fp->fp_workdir = old_workdir_ip;
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return(NIL_INODE); /* we couldn't open final directory */
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}
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/* The path consisting only of "/" is a special case, check for it. */
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if (string[0] == '\0') return(ldip);
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/* Get final component of the path. */
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rip = advance(ldip, string);
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if (rip != NIL_INODE && (rip->i_mode & I_TYPE) == I_SYMBOLIC_LINK) {
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if (++loops > MAX_SYM_LOOPS) {
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put_inode(rip);
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put_inode(ldip);
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fp->fp_workdir = old_workdir_ip;
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err_code = ELOOP;
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return(NIL_INODE);
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}
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rip = slink_traverse(rip, path, string, ldip);
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slink_found = TRUE;
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fp->fp_workdir = rip; /* cd to link's starting dir */
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put_inode(rip);
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}
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put_inode(ldip);
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} while (slink_found);
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fp->fp_workdir = old_workdir_ip;
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return(rip);
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}
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/*===========================================================================*
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* last_dir *
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*===========================================================================*/
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PUBLIC struct inode *last_dir(path, string)
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char *path; /* the path name to be parsed */
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char string[NAME_MAX]; /* the final component is returned here */
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{
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/* Given a path, 'path', located in the fs address space, parse it as
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* far as the last directory, fetch the inode for the last directory into
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* the inode table, and return a pointer to the inode. In
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* addition, return the final component of the path in 'string'.
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* If the last directory can't be opened, return NIL_INODE and
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* the reason for failure in 'err_code'.
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*/
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register struct inode *rip;
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register char *new_name;
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register struct inode *new_ip;
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int loops = 0; /* count symlink traversals */
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/* Is the path absolute or relative? Initialize 'rip' accordingly. */
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rip = (*path == '/' ? fp->fp_rootdir : fp->fp_workdir);
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/* If dir has been removed or path is empty, return ENOENT. */
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if (rip->i_nlinks == 0 || *path == '\0') {
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err_code = ENOENT;
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return(NIL_INODE);
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}
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dup_inode(rip); /* inode will be returned with put_inode */
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/* Scan the path component by component. */
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while (TRUE) {
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/* Extract one component. */
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if ( (new_name = get_name(path, string)) == (char*) 0) {
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put_inode(rip); /* bad path in user space */
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return(NIL_INODE);
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}
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if (*new_name == '\0') {
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if ( (rip->i_mode & I_TYPE) == I_DIRECTORY) {
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return(rip); /* normal exit */
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} else {
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/* last file of path prefix is not a directory */
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put_inode(rip);
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err_code = ENOTDIR;
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return(NIL_INODE);
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}
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}
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/* There is more path. Keep parsing. */
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new_ip = advance(rip, string);
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if (new_ip == NIL_INODE) {
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put_inode(rip);
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return(NIL_INODE);
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}
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/* The call to advance() succeeded. Fetch next component. */
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if ((new_ip->i_mode & I_TYPE) == I_SYMBOLIC_LINK) {
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if (++loops > MAX_SYM_LOOPS) {
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err_code = ELOOP;
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put_inode(rip);
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put_inode(new_ip);
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return(NIL_INODE);
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}
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new_ip = slink_traverse(new_ip, path, string, rip);
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} else
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path = new_name;
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put_inode(rip); /* rip either obsolete or irrelevant */
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rip = new_ip;
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}
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}
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/*===========================================================================*
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* get_name *
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*===========================================================================*/
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PRIVATE char *get_name(old_name, string)
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char *old_name; /* path name to parse */
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char string[NAME_MAX]; /* component extracted from 'old_name' */
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{
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/* Given a pointer to a path name in fs space, 'old_name', copy the next
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* component to 'string' and pad with zeros. A pointer to that part of
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* the name as yet unparsed is returned. Roughly speaking,
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* 'get_name' = 'old_name' - 'string'.
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*
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* This routine follows the standard convention that /usr/ast, /usr//ast,
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* //usr///ast and /usr/ast/ are all equivalent.
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*/
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register int c;
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register char *np, *rnp;
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np = string; /* 'np' points to current position */
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rnp = old_name; /* 'rnp' points to unparsed string */
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while ( (c = *rnp) == '/') rnp++; /* skip leading slashes */
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/* Copy the unparsed path, 'old_name', to the array, 'string'. */
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while ( rnp < &old_name[PATH_MAX] && c != '/' && c != '\0') {
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if (np < &string[NAME_MAX]) *np++ = c;
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c = *++rnp; /* advance to next character */
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}
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/* To make /usr/ast/ equivalent to /usr/ast, skip trailing slashes. */
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while (c == '/' && rnp < &old_name[PATH_MAX]) c = *++rnp;
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if (np < &string[NAME_MAX]) *np = '\0'; /* Terminate string */
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if (rnp >= &old_name[PATH_MAX]) {
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err_code = ENAMETOOLONG;
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return((char *) 0);
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}
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return(rnp);
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}
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/*===========================================================================*
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* advance *
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*===========================================================================*/
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PUBLIC struct inode *advance(dirp, string)
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struct inode *dirp; /* inode for directory to be searched */
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char string[NAME_MAX]; /* component name to look for */
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{
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/* Given a directory and a component of a path, look up the component in
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* the directory, find the inode, open it, and return a pointer to its inode
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* slot. If it can't be done, return NIL_INODE.
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*/
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register struct inode *rip;
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struct inode *rip2;
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register struct super_block *sp;
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int r, inumb;
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dev_t mnt_dev;
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ino_t numb;
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/* If 'string' is empty, yield same inode straight away. */
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if (string[0] == '\0') { return(get_inode(dirp->i_dev, (int) dirp->i_num)); }
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/* Check for NIL_INODE. */
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if (dirp == NIL_INODE) { return(NIL_INODE); }
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/* If 'string' is not present in the directory, signal error. */
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if ( (r = search_dir(dirp, string, &numb, LOOK_UP)) != OK) {
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err_code = r;
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return(NIL_INODE);
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}
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/* Don't go beyond the current root directory, unless the string is dot2. */
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if (dirp == fp->fp_rootdir && strcmp(string, "..") == 0 && string != dot2)
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return(get_inode(dirp->i_dev, (int) dirp->i_num));
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/* The component has been found in the directory. Get inode. */
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if ( (rip = get_inode(dirp->i_dev, (int) numb)) == NIL_INODE) {
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return(NIL_INODE);
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}
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if (rip->i_num == ROOT_INODE)
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if (dirp->i_num == ROOT_INODE) {
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if (string[1] == '.') {
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for (sp = &super_block[1]; sp < &super_block[NR_SUPERS]; sp++){
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if (sp->s_dev == rip->i_dev) {
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/* Release the root inode. Replace by the
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* inode mounted on.
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*/
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put_inode(rip);
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mnt_dev = sp->s_imount->i_dev;
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inumb = (int) sp->s_imount->i_num;
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rip2 = get_inode(mnt_dev, inumb);
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rip = advance(rip2, string);
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put_inode(rip2);
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break;
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}
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}
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}
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}
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if (rip == NIL_INODE) return(NIL_INODE);
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/* See if the inode is mounted on. If so, switch to root directory of the
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* mounted file system. The super_block provides the linkage between the
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* inode mounted on and the root directory of the mounted file system.
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*/
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while (rip != NIL_INODE && rip->i_mount == I_MOUNT) {
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/* The inode is indeed mounted on. */
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for (sp = &super_block[0]; sp < &super_block[NR_SUPERS]; sp++) {
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if (sp->s_imount == rip) {
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/* Release the inode mounted on. Replace by the
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* inode of the root inode of the mounted device.
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*/
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put_inode(rip);
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rip = get_inode(sp->s_dev, ROOT_INODE);
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break;
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}
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}
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}
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return(rip); /* return pointer to inode's component */
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}
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/*===========================================================================*
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* search_dir *
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*===========================================================================*/
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PUBLIC int search_dir(ldir_ptr, string, numb, flag)
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register struct inode *ldir_ptr; /* ptr to inode for dir to search */
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char string[NAME_MAX]; /* component to search for */
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ino_t *numb; /* pointer to inode number */
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int flag; /* LOOK_UP, ENTER, DELETE or IS_EMPTY */
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{
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/* This function searches the directory whose inode is pointed to by 'ldip':
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* if (flag == ENTER) enter 'string' in the directory with inode # '*numb';
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* if (flag == DELETE) delete 'string' from the directory;
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* if (flag == LOOK_UP) search for 'string' and return inode # in 'numb';
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* if (flag == IS_EMPTY) return OK if only . and .. in dir else ENOTEMPTY;
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*
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* if 'string' is dot1 or dot2, no access permissions are checked.
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*/
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register struct direct *dp = NULL;
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register struct buf *bp = NULL;
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int i, r, e_hit, t, match;
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mode_t bits;
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off_t pos;
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unsigned new_slots, old_slots;
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block_t b;
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struct super_block *sp;
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int extended = 0;
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/* If 'ldir_ptr' is not a pointer to a dir inode, error. */
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if ( (ldir_ptr->i_mode & I_TYPE) != I_DIRECTORY) return(ENOTDIR);
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r = OK;
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if (flag != IS_EMPTY) {
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bits = (flag == LOOK_UP ? X_BIT : W_BIT | X_BIT);
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if (string == dot1 || string == dot2) {
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if (flag != LOOK_UP) r = read_only(ldir_ptr);
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/* only a writable device is required. */
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}
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else r = forbidden(ldir_ptr, bits); /* check access permissions */
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}
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if (r != OK) return(r);
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/* Step through the directory one block at a time. */
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old_slots = (unsigned) (ldir_ptr->i_size/DIR_ENTRY_SIZE);
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new_slots = 0;
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e_hit = FALSE;
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match = 0; /* set when a string match occurs */
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for (pos = 0; pos < ldir_ptr->i_size; pos += ldir_ptr->i_sp->s_block_size) {
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b = read_map(ldir_ptr, pos); /* get block number */
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/* Since directories don't have holes, 'b' cannot be NO_BLOCK. */
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bp = get_block(ldir_ptr->i_dev, b, NORMAL); /* get a dir block */
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if (bp == NO_BLOCK)
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panic(__FILE__,"get_block returned NO_BLOCK", NO_NUM);
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/* Search a directory block. */
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for (dp = &bp->b_dir[0];
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dp < &bp->b_dir[NR_DIR_ENTRIES(ldir_ptr->i_sp->s_block_size)];
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dp++) {
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if (++new_slots > old_slots) { /* not found, but room left */
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if (flag == ENTER) e_hit = TRUE;
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break;
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}
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/* Match occurs if string found. */
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if (flag != ENTER && dp->d_ino != 0) {
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if (flag == IS_EMPTY) {
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/* If this test succeeds, dir is not empty. */
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if (strcmp(dp->d_name, "." ) != 0 &&
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strcmp(dp->d_name, "..") != 0) match = 1;
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} else {
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if (strncmp(dp->d_name, string, NAME_MAX) == 0) {
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match = 1;
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}
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}
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}
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if (match) {
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/* LOOK_UP or DELETE found what it wanted. */
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r = OK;
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if (flag == IS_EMPTY) r = ENOTEMPTY;
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else if (flag == DELETE) {
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/* Save d_ino for recovery. */
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t = NAME_MAX - sizeof(ino_t);
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*((ino_t *) &dp->d_name[t]) = dp->d_ino;
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dp->d_ino = 0; /* erase entry */
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bp->b_dirt = DIRTY;
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ldir_ptr->i_update |= CTIME | MTIME;
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ldir_ptr->i_dirt = DIRTY;
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} else {
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sp = ldir_ptr->i_sp; /* 'flag' is LOOK_UP */
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*numb = conv4(sp->s_native, (int) dp->d_ino);
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}
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put_block(bp, DIRECTORY_BLOCK);
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return(r);
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}
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/* Check for free slot for the benefit of ENTER. */
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if (flag == ENTER && dp->d_ino == 0) {
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e_hit = TRUE; /* we found a free slot */
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break;
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}
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}
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/* The whole block has been searched or ENTER has a free slot. */
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if (e_hit) break; /* e_hit set if ENTER can be performed now */
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put_block(bp, DIRECTORY_BLOCK); /* otherwise, continue searching dir */
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}
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/* The whole directory has now been searched. */
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if (flag != ENTER) {
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return(flag == IS_EMPTY ? OK : ENOENT);
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}
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/* This call is for ENTER. If no free slot has been found so far, try to
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* extend directory.
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*/
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if (e_hit == FALSE) { /* directory is full and no room left in last block */
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new_slots++; /* increase directory size by 1 entry */
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if (new_slots == 0) return(EFBIG); /* dir size limited by slot count */
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if ( (bp = new_block(ldir_ptr, ldir_ptr->i_size)) == NIL_BUF)
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return(err_code);
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dp = &bp->b_dir[0];
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extended = 1;
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}
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/* 'bp' now points to a directory block with space. 'dp' points to slot. */
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(void) memset(dp->d_name, 0, (size_t) NAME_MAX); /* clear entry */
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for (i = 0; string[i] && i < NAME_MAX; i++) dp->d_name[i] = string[i];
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sp = ldir_ptr->i_sp;
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dp->d_ino = conv4(sp->s_native, (int) *numb);
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bp->b_dirt = DIRTY;
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put_block(bp, DIRECTORY_BLOCK);
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ldir_ptr->i_update |= CTIME | MTIME; /* mark mtime for update later */
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ldir_ptr->i_dirt = DIRTY;
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if (new_slots > old_slots) {
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ldir_ptr->i_size = (off_t) new_slots * DIR_ENTRY_SIZE;
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/* Send the change to disk if the directory is extended. */
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if (extended) rw_inode(ldir_ptr, WRITING);
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}
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return(OK);
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}
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/*===========================================================================*
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* slink_traverse *
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*===========================================================================*/
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PUBLIC struct inode *slink_traverse(rip, path, string, ldip)
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register struct inode *rip;
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char *path;
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char *string;
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register struct inode *ldip;
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{
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/* copy path out of symlink's disk block -- return inode pointer to
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* the directory that the path infers */
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register char *p, *q;
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char temp[PATH_MAX];
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struct buf *bp;
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block_t b;
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b = read_map(rip, 0);
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bp = get_block(rip->i_dev, b, NORMAL); /* get the pathname block */
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memcpy(temp, bp->b_data, rip->i_size);
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temp[rip->i_size] = '\0';
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put_block(bp, NORMAL);
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q = strstr(path, string);
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if ((p = strchr(q, '/')) != NULL && (q + strlen(string)) == p) {
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strcat(temp, p);
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}
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strcpy(path, temp);
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put_inode(rip);
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rip = (*path == '/') ? fp->fp_rootdir : ldip;
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dup_inode(rip);
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return (rip);
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}
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/** path.c **/
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