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Annotation of Net2/arch/i386/stand/bmap.c, revision 1.1.1.1

1.1       root        1: /*
                      2:  * Copyright (c) 1982, 1986, 1989 Regents of the University of California.
                      3:  * All rights reserved.
                      4:  *
                      5:  * Redistribution and use in source and binary forms, with or without
                      6:  * modification, are permitted provided that the following conditions
                      7:  * are met:
                      8:  * 1. Redistributions of source code must retain the above copyright
                      9:  *    notice, this list of conditions and the following disclaimer.
                     10:  * 2. Redistributions in binary form must reproduce the above copyright
                     11:  *    notice, this list of conditions and the following disclaimer in the
                     12:  *    documentation and/or other materials provided with the distribution.
                     13:  * 3. All advertising materials mentioning features or use of this software
                     14:  *    must display the following acknowledgement:
                     15:  *     This product includes software developed by the University of
                     16:  *     California, Berkeley and its contributors.
                     17:  * 4. Neither the name of the University nor the names of its contributors
                     18:  *    may be used to endorse or promote products derived from this software
                     19:  *    without specific prior written permission.
                     20:  *
                     21:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
                     22:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
                     23:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
                     24:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
                     25:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
                     26:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
                     27:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
                     28:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
                     29:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
                     30:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
                     31:  * SUCH DAMAGE.
                     32:  *
                     33:  *     derived from: @(#)ufs_bmap.c    7.13 (Berkeley) 5/8/91
                     34:  */
                     35: 
                     36: #include "param.h"
                     37: #include "dinode.h"
                     38: #include "fs.h"
                     39: #include "errno.h"
                     40: 
                     41: /*
                     42:  * Bmap converts a the logical block number of a file
                     43:  * to its physical block number on the disk. The conversion
                     44:  * is done by using the logical block number to index into
                     45:  * the array of block pointers described by the dinode.
                     46:  */
                     47: extern struct fs *fs;
                     48: extern int bdev;
                     49: 
                     50: static daddr_t bap[2*1024];
                     51: static daddr_t bnobap;
                     52: 
                     53: bmap(dip, bn, bnp)
                     54:        register struct dinode *dip;
                     55:        register daddr_t bn;
                     56:        daddr_t *bnp;
                     57: {
                     58:        register daddr_t nb;
                     59:        int i, j, sh;
                     60:        int error;
                     61: 
                     62: /*fprintf(stderr, "bmap %d ", bn);*/
                     63:        if (bn < 0)
                     64:                return (EFBIG);
                     65: 
                     66:        /*
                     67:         * The first NDADDR blocks are direct blocks
                     68:         */
                     69:        if (bn < NDADDR) {
                     70:                nb = dip->di_db[bn];
                     71:                if (nb == 0) {
                     72:                        *bnp = (daddr_t)-1;
                     73: /*fprintf(stderr, "%d\n", *bnp);*/
                     74:                        return (0);
                     75:                }
                     76:                *bnp = fsbtodb(fs, nb);
                     77: /*fprintf(stderr, "%d\n", *bnp);*/
                     78:                return (0);
                     79:        }
                     80:        /*
                     81:         * Determine the number of levels of indirection.
                     82:         */
                     83:        sh = 1;
                     84:        bn -= NDADDR;
                     85:        for (j = NIADDR; j > 0; j--) {
                     86:                sh *= NINDIR(fs);
                     87:                if (bn < sh)
                     88:                        break;
                     89:                bn -= sh;
                     90:        }
                     91:        if (j == 0)
                     92:                return (EFBIG);
                     93:        /*
                     94:         * Fetch through the indirect blocks.
                     95:         */
                     96:        nb = dip->di_ib[NIADDR - j];
                     97:        if (nb == 0) {
                     98:                *bnp = (daddr_t)-1;
                     99: /*fprintf(stderr, "%d\n", *bnp);*/
                    100:                return (0);
                    101:        }
                    102:        for (; j <= NIADDR; j++) {
                    103:                daddr_t bno = fsbtodb(fs, nb);
                    104: 
                    105:                if (bnobap != bno &&
                    106: (error = bread(bdev, bno, &bap,
                    107:                        (int)fs->fs_bsize))) {
                    108:                        return (error);
                    109:                }
                    110:                bnobap = bno;
                    111:                sh /= NINDIR(fs);
                    112:                i = (bn / sh) % NINDIR(fs);
                    113:                nb = bap[i];
                    114:                if (nb == 0) {
                    115:                        *bnp = (daddr_t)-1;
                    116: /*fprintf(stderr, "%d\n", *bnp);*/
                    117:                        return (0);
                    118:                }
                    119:        }
                    120:        *bnp = fsbtodb(fs, nb);
                    121: /*fprintf(stderr, "%d\n", *bnp);*/
                    122:        return (0);
                    123: }

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