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