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/* This file contains the procedures that look up path names in the directory

* system and determine the inode number that goes with a given path name.

*/

/* Methods:

 * eat_path:        the 'main' routine of the path-to-inode conversion mechanism

 * last_dir:        find the final directory on a given path

 * advance:     parse one component of a path name

 * search_dir:      search a directory for a string and return its inode number

 * search_dir_ex:   used for extended versions

 */

#include <string.h>

#include "fs.h"

#include "block.h"

#include "file.h"

#include "fproc.h"

#include "inode.h"

#include "super.h"

static char *get_name(char *old_name, char *string, int string_length);

inode_t *eat_path(char *path)

{

    /* Parse the path 'path' and put its inode in the inode table. If not possible,

     * return NIL_INODE as function value and an error code in 'err_code'.

     */

    register inode_t *ldip, *rip;

    super_block_t *sp;

    int name_len;

    char string[name_len];        /* hold 1 path component name here */

    name_len = NAME_MAX;

    if ((sp = get_super()) == NIL_SUPER)

        return NIL_INODE;

    if (sp->s_extend) {

        name_len = NAME_MAX_EX;

    }

    /* First open the path down to the final directory. */

    if ( (ldip = last_dir(path, string, name_len)) == NIL_INODE)

        return NIL_INODE;      /* we couldn't open final directory */

    /* The path consisting only of "/" is a special case, check for it. */

    if (string[0] == '\0')

        return ldip;

    /* Get final component of the path. */

    rip = advance(ldip, string, name_len);

    put_inode(ldip);

    return rip;

}

inode_t *last_dir(char *path, char *string, int string_length)

{

    /* Given a path, 'path', located in the fs address space, parse it as

     * far as the last directory, fetch the inode for the last directory into

     * the inode table, and return a pointer to the inode.  In

     * addition, return the final component of the path in 'string'.

     * If the last directory can't be opened, return NIL_INODE and

     * the reason for failure in 'err_code'.

     */

    register inode_t *rip;

    register char *new_name;

    register inode_t *new_ip;

    /* Is the path absolute or relative?  Initialize 'rip' accordingly. */

    rip = (*path == '/' ? fp->fp_rootdir : fp->fp_workdir);

    /* If dir has been removed or path is empty, return FS_ENOENT. */

    if (rip->i_nlinks == 0  ||  *path == '\0') {

        err_code = FS_ENOENT;

        return NIL_INODE;

    }

    dup_inode(rip);     /* inode will be returned with put_inode */

    /* Scan the path component by component. */

    while (TRUE) {

        /* Extract one component. */

        if ( (new_name = get_name(path, string, string_length)) == (char*) 0) {

            put_inode(rip); /* bad path in user space */

            return NIL_INODE;

            }

        if (*new_name == '\0')

        {

            if ( (rip->i_mode & I_TYPE) == I_DIRECTORY)

                return rip;    /* normal exit */

            else {

                /* last file of path prefix is not a directory */

                put_inode(rip);

                err_code = FS_ENOTDIR;         

                return NIL_INODE;

            }

        }

            /* There is more path.  Keep parsing. */

        new_ip = advance(rip, string, string_length);

        put_inode(rip);

        if (new_ip == NIL_INODE) {

            return NIL_INODE;

        }

        /* The call to advance() succeeded.  Fetch next component. */

        path = new_name;

        rip = new_ip;

    }

}

char *get_name(char *old_name, char *string, int string_length)

{

    /* Given a pointer to a path name in fs space, 'old_name', copy the next

     * component to 'string' and pad with zeros.  A pointer to that part of

     * the name as yet unparsed is returned.  Roughly speaking,

     * 'get_name' = 'old_name' - 'string'.

     *

     * This routine follows the standard convention that /usr/ast, /usr//ast,

     * //usr///ast and /usr/ast/ are all equivalent.

     */

    register int c;

    register char *np, *rnp;

    np = string;                  /* 'np' points to current position */

    rnp = old_name;               /* 'rnp' points to unparsed string */

    while ((c = *rnp) == '/')

        rnp++;     /* skip leading slashes */

    /* Copy the unparsed path, 'old_name', to the array, 'string'. */

    while ( rnp < &old_name[PATH_MAX]  &&  c != '/'   &&  c != '\0') {

        if (np < &string[string_length])

            *np++ = c;

        c = *++rnp;             /* advance to next character */

    }

    /* To make /usr/ast/ equivalent to /usr/ast, skip trailing slashes. */

    while (c == '/' && rnp < &old_name[PATH_MAX])

        c = *++rnp;

    /* Padding with zeroes */

    if (np < &string[string_length])

        *np = '\0';       /* Terminate string */

    if (rnp >= &old_name[PATH_MAX]) {

        err_code = FS_ENAMETOOLONG;

        return((char *) 0);

    }

    return rnp;

}

inode_t *advance(inode_t *dirp, char *string, int string_length)

{

    /* Given a directory and a component of a path, look up the component in

     * the directory, find the inode, open it, and return a pointer to its inode

     * slot.  If it can't be done, return NIL_INODE.

     */

    register inode_t *rip;

    int r;

    ino_t numb;

    /* If 'string' is empty, yield same inode straight away. */

    if (string[0] == '\0')

        return get_inode((int) dirp->i_num);

    /* Check for NIL_INODE. */

    if (dirp == NIL_INODE)

        return NIL_INODE;

    /* If 'string' is not present in the directory, signal error. */

    if (dirp->i_sp->s_extend) {

        r = search_dir_ex(dirp, string, &numb, LOOK_UP);

    }

    else {

        r = search_dir(dirp, string, &numb, LOOK_UP);

    }

    if (r != OK) {

        err_code = r;

        return NIL_INODE;

    }

    /* Don't go beyond the current root directory */

    if (dirp == fp->fp_rootdir && strcmp(string, "..") == 0)

        return(get_inode((int) dirp->i_num));

    /* The component has been found in the directory.  Get inode. */

    if ( (rip = get_inode((int) numb)) == NIL_INODE)

        return NIL_INODE;

    return rip;          /* return pointer to inode's component */

}

int search_dir(register inode_t *ldir_ptr, char string[NAME_MAX], ino_t *numb, int flag)

{

    /* This function searches the directory whose inode is pointed to by 'ldip':

     * if (flag == LOOK_UP) search for 'string' and return inode # in 'numb';

     * if (flag == IS_EMPTY) return OK if only . and .. in dir else ENOTEMPTY;

     */

    register direct_t *dp;

    register block_t *bp;

    int r, match;

    offset_t pos;

    unsigned old_slots;

    block_num_t b;

    /* If 'ldir_ptr' is not a pointer to a dir inode, error. */

    if ((ldir_ptr->i_mode & I_TYPE) != I_DIRECTORY)

        return FS_ENOTDIR;

    r = OK;

    /* Step through the directory one block at a time. */

    old_slots = (unsigned)(ldir_ptr->i_size/DIR_ENTRY_SIZE);  

    match = 0;                    /* set when a string match occurs */

    for (pos = 0; pos < ldir_ptr->i_size; pos += BLOCK_SIZE) {

        b = read_map(ldir_ptr, pos);    /* get block number */

        /* Since directories don't have holes, 'b' cannot be NO_BLOCK. */

        bp = get_block(b);     /* get a dir block */

        /* Search a directory block. */

        for (dp = &bp->b.b__dir[0]; dp < &bp->b.b__dir[NR_DIR_ENTRIES]; dp++) {

                    /* Match occurs if string found. */

                    if (dp->d_ino != 0) {

                if (flag == IS_EMPTY) {

                    /* If this test succeeds, dir is not empty. */

                    if (strcmp(dp->d_name, "." ) != 0 &&

                        strcmp(dp->d_name, "..") != 0)

                        match = 1;

                            }

                else {

                    if (fs_strncmp(dp->d_name, string, NAME_MAX) == 0)

                        match = 1;

                }

            }

            if (match) {

                /* LOOK_UP or DELETE found what it wanted. */

                r = OK;

                if (flag == IS_EMPTY) {

                    r = FS_ENOTEMPTY;

                }

                else {

                    *numb =  (int) dp->d_ino;

                }

                return r;

            }

        }  

    }

    /* The whole directory has now been searched. */

    return(flag == IS_EMPTY ? OK : FS_ENOENT); 

}

int search_dir_ex(register inode_t *ldir_ptr, char string[NAME_MAX_EX], ino_t *numb, int flag)

{

    /* Same as above, but for extened directory etries - 30 chars in name of file. */

    register directex_t *dp;

    register block_t *bp;

    int r, match;

    offset_t pos;

    unsigned old_slots;

    block_num_t b;

    /* If 'ldir_ptr' is not a pointer to a dir inode, error. */

    if ( (ldir_ptr->i_mode & I_TYPE) != I_DIRECTORY)

        return FS_ENOTDIR;

    r = OK;

    /* Step through the directory one block at a time. */

    old_slots = (unsigned)(ldir_ptr->i_size/DIR_ENTRY_SIZE_EX);

    match = 0;                    /* set when a string match occurs */

    for (pos = 0; pos < ldir_ptr->i_size; pos += BLOCK_SIZE) {

        b = read_map(ldir_ptr, pos);    /* get block number */

        /* Since directories don't have holes, 'b' cannot be NO_BLOCK. */

        bp = get_block(b);     /* get a dir block */

        /* Search a directory block. */

        for (dp = &bp->b.b__direx[0]; dp < &bp->b.b__direx[NR_DIR_ENTRIES_EX]; dp++) {

            /* Match occurs if string found. */

            if (dp->d_ino != 0) {

                if (flag == IS_EMPTY) {

                /* If this test succeeds, dir is not empty. */

                    if (strcmp(dp->d_name, "." ) != 0 &&

                        strcmp(dp->d_name, "..") != 0) match = 1;

                            }

                else {

                    if (fs_strncmp(dp->d_name, string, NAME_MAX_EX) == 0)

                        match = 1;

                }

            }

            if (match) {

                /* LOOK_UP or DELETE found what it wanted. */

                r = OK;

                if (flag == IS_EMPTY) {

                    r = FS_ENOTEMPTY;

                }

                else {

                    *numb =  (int)dp->d_ino;

                }

                return r;

            }

        }        

    }

    /* The whole directory has now been searched. */

    return(flag == IS_EMPTY ? OK : FS_ENOENT); 

}