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Annotation of driverkit/libDriver/label_subr.c, revision 1.1

1.1     ! root        1: /*
        !             2:  * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
        !             3:  *
        !             4:  * @APPLE_LICENSE_HEADER_START@
        !             5:  * 
        !             6:  * Portions Copyright (c) 1999 Apple Computer, Inc.  All Rights
        !             7:  * Reserved.  This file contains Original Code and/or Modifications of
        !             8:  * Original Code as defined in and that are subject to the Apple Public
        !             9:  * Source License Version 1.1 (the "License").  You may not use this file
        !            10:  * except in compliance with the License.  Please obtain a copy of the
        !            11:  * License at http://www.apple.com/publicsource and read it before using
        !            12:  * this file.
        !            13:  * 
        !            14:  * The Original Code and all software distributed under the License are
        !            15:  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
        !            16:  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
        !            17:  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
        !            18:  * FITNESS FOR A PARTICULAR PURPOSE OR NON- INFRINGEMENT.  Please see the
        !            19:  * License for the specific language governing rights and limitations
        !            20:  * under the License.
        !            21:  * 
        !            22:  * @APPLE_LICENSE_HEADER_END@
        !            23:  */
        !            24: /*     Copyright (c) 1992 NeXT Computer, Inc.  All rights reserved. 
        !            25:  *
        !            26:  * label_subr.c - machine-independent disk label routines
        !            27:  *
        !            28:  * HISTORY
        !            29:  * 01-Apr-92    Doug Mitchell at NeXT
        !            30:  *      Created.
        !            31:  */
        !            32: #import <bsd/sys/param.h> 
        !            33: #import <bsd/dev/disk_label.h>
        !            34: #import <driverkit/disk_label.h>
        !            35: #import <driverkit/diskstruct.h>
        !            36: #import <architecture/byte_order.h>
        !            37: 
        !            38: 
        !            39: /*
        !            40:  * Inlines used to manipulate m68k-style disk label fields.
        !            41:  */
        !            42: static inline unsigned int
        !            43: get_word(const void *src)
        !            44: {
        !            45:        return ( NXSwapBigIntToHost(*((unsigned int *)src)));
        !            46: }
        !            47: 
        !            48: static inline void
        !            49: put_word(unsigned s, void *dest)
        !            50: {
        !            51:        *((unsigned int *)dest) = NXSwapHostIntToBig(s);
        !            52: }
        !            53: 
        !            54: 
        !            55: static inline unsigned short
        !            56: get_short(const void *src)
        !            57: {
        !            58:        return ( NXSwapBigShortToHost(*((unsigned short *)src)));
        !            59: }
        !            60: 
        !            61: static inline void
        !            62: put_short(unsigned short s, void *dest)
        !            63: {
        !            64:        *((unsigned short *)dest) = NXSwapHostShortToBig(s);
        !            65: }
        !            66: 
        !            67: /*
        !            68:  * Machine-independent version of kernel's checksum_16().
        !            69:  * *wp is a raw m68k-style label.
        !            70:  */
        !            71: unsigned short 
        !            72: checksum16(unsigned short *wp, int num_shorts)
        !            73: {
        !            74:        int sum1 = 0;
        !            75:        int sum2;
        !            76: 
        !            77:        while (num_shorts--){
        !            78:                sum1 += NXSwapBigShortToHost(*wp);
        !            79:                wp++;
        !            80:        }
        !            81:        sum2 = ((sum1 & 0xffff0000) >> 16) + (sum1 & 0xffff);
        !            82:        if(sum2 > 65535) {
        !            83:                sum2 -= 65535;
        !            84:        }
        !            85:        return sum2;
        !            86: }
        !            87: 
        !            88: /*
        !            89:  * Validate an m68k-style label. Returns NULL if good, else returns pointer
        !            90:  * to an error string describing what is wrong with the label.
        !            91:  */
        !            92: char *
        !            93: check_label(char *raw_label,                   // as it came off disk
        !            94:        int block_num)  
        !            95: {
        !            96:        unsigned short  sum;
        !            97:        unsigned short  cksum;
        !            98:        unsigned short  size;
        !            99:        void            *dl_cksump;
        !           100:        int              version;
        !           101:        int             label_blkno;
        !           102:        
        !           103:        version = get_word(raw_label + DISK_LABEL_DL_VERSION);
        !           104:        if(version == DL_V1 || version == DL_V2) {
        !           105:                size = SIZEOF_DISK_LABEL_T;
        !           106:                dl_cksump = raw_label + DISK_LABEL_DL_CHECKSUM;
        !           107:        } 
        !           108:        else if(version == DL_V3) {
        !           109:                size = SIZEOF_DISK_LABEL_T - SIZEOF_DL_UN_T;
        !           110:                dl_cksump = raw_label + DISK_LABEL_DL_UN;
        !           111:        } 
        !           112:        else {
        !           113:                return "Bad disk label magic number";
        !           114:        }
        !           115:        label_blkno = get_word(raw_label + DISK_LABEL_DL_LABEL_BLKNO);
        !           116:        if(label_blkno != block_num) {
        !           117:                return "Label in wrong location";
        !           118:        }
        !           119:                
        !           120:        /*
        !           121:         * Block number in label has to be 0 for checksum calculation.
        !           122:         */
        !           123:        put_word(0, raw_label + DISK_LABEL_DL_LABEL_BLKNO);
        !           124:        cksum = get_short(dl_cksump);
        !           125:        put_short(0, dl_cksump);
        !           126:        sum = checksum16((unsigned short *)raw_label, size >> 1);
        !           127:        if (sum != cksum) {
        !           128:                return "Label checksum error";
        !           129:        }
        !           130:        
        !           131:        /*
        !           132:         * Success. Restore block number.
        !           133:         */
        !           134:        put_word(block_num, raw_label + DISK_LABEL_DL_LABEL_BLKNO);
        !           135:        put_short(cksum, dl_cksump);
        !           136:        return NULL;
        !           137: }

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