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Annotation of Gnu-Mach/kern/strings.c, revision 1.1

1.1     ! root        1: /* 
        !             2:  * Mach Operating System
        !             3:  * Copyright (c) 1993 Carnegie Mellon University
        !             4:  * All Rights Reserved.
        !             5:  * 
        !             6:  * Permission to use, copy, modify and distribute this software and its
        !             7:  * documentation is hereby granted, provided that both the copyright
        !             8:  * notice and this permission notice appear in all copies of the
        !             9:  * software, derivative works or modified versions, and any portions
        !            10:  * thereof, and that both notices appear in supporting documentation.
        !            11:  * 
        !            12:  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
        !            13:  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
        !            14:  * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
        !            15:  * 
        !            16:  * Carnegie Mellon requests users of this software to return to
        !            17:  * 
        !            18:  *  Software Distribution Coordinator  or  [email protected]
        !            19:  *  School of Computer Science
        !            20:  *  Carnegie Mellon University
        !            21:  *  Pittsburgh PA 15213-3890
        !            22:  * 
        !            23:  * any improvements or extensions that they make and grant Carnegie Mellon
        !            24:  * the rights to redistribute these changes.
        !            25:  */
        !            26: /*
        !            27:  *     File: strings.c
        !            28:  *     Author: Robert V. Baron, Carnegie Mellon University
        !            29:  *     Date:   ??/92
        !            30:  *
        !            31:  *     String functions.
        !            32:  */
        !            33: 
        !            34: #include <kern/strings.h>      /* make sure we sell the truth */
        !            35: 
        !            36: #ifdef strcpy
        !            37: #undef strcmp
        !            38: #undef strncmp
        !            39: #undef strcpy
        !            40: #undef strncpy
        !            41: #undef strlen
        !            42: #endif
        !            43: 
        !            44: /*
        !            45:  * Abstract:
        !            46:  *     strcmp (s1, s2) compares the strings "s1" and "s2".
        !            47:  *     It returns 0 if the strings are identical. It returns
        !            48:  *     > 0 if the first character that differs in the two strings
        !            49:  *     is larger in s1 than in s2 or if s1 is longer than s2 and 
        !            50:  *     the contents are identical up to the length of s2.
        !            51:  *     It returns < 0 if the first differing character is smaller 
        !            52:  *     in s1 than in s2 or if s1 is shorter than s2 and the
        !            53:  *     contents are identical upto the length of s1.
        !            54:  */
        !            55: 
        !            56: int
        !            57: strcmp(
        !            58:        register const char *s1,
        !            59:        register const char *s2)
        !            60: {
        !            61:        register unsigned int a, b;
        !            62: 
        !            63:        do {
        !            64:                a = *s1++;
        !            65:                b = *s2++;
        !            66:                if (a != b)
        !            67:                        return a-b;     /* includes case when
        !            68:                                           'a' is zero and 'b' is not zero
        !            69:                                           or vice versa */
        !            70:        } while (a != '\0');
        !            71: 
        !            72:        return 0;       /* both are zero */
        !            73: }
        !            74: 
        !            75: 
        !            76: /*
        !            77:  * Abstract:
        !            78:  *     strncmp (s1, s2, n) compares the strings "s1" and "s2"
        !            79:  *     in exactly the same way as strcmp does.  Except the
        !            80:  *     comparison runs for at most "n" characters.
        !            81:  */
        !            82: 
        !            83: int
        !            84: strncmp(
        !            85:        register const char *s1,
        !            86:        register const char *s2,
        !            87:        unsigned long n)
        !            88: {
        !            89:        register unsigned int a, b;
        !            90: 
        !            91:        while (n != 0) {
        !            92:                a = *s1++;
        !            93:                b = *s2++;
        !            94:                if (a != b)
        !            95:                        return a-b;     /* includes case when
        !            96:                                           'a' is zero and 'b' is not zero
        !            97:                                           or vice versa */
        !            98:                if (a == '\0')
        !            99:                        return 0;       /* both are zero */
        !           100:                n--;
        !           101:        }
        !           102: 
        !           103:        return 0;
        !           104: }
        !           105: 
        !           106: 
        !           107: /*
        !           108:  * Abstract:
        !           109:  *     strcpy copies the contents of the string "from" including 
        !           110:  *     the null terminator to the string "to". A pointer to "to"
        !           111:  *     is returned.
        !           112:  */
        !           113: 
        !           114: char *
        !           115: strcpy(
        !           116:        register char *to,
        !           117:        register const char *from)
        !           118: {
        !           119:        register char *ret = to;
        !           120: 
        !           121:        while ((*to++ = *from++) != '\0')
        !           122:                continue;
        !           123: 
        !           124:        return ret;
        !           125: }
        !           126: 
        !           127: /*
        !           128:  * Abstract:
        !           129:  *     strncpy copies "count" characters from the "from" string to
        !           130:  *     the "to" string. If "from" contains less than "count" characters
        !           131:  *     "to" will be padded with null characters until exactly "count"
        !           132:  *     characters have been written. The return value is a pointer
        !           133:  *     to the "to" string.
        !           134:  */
        !           135: 
        !           136: char *
        !           137: strncpy(
        !           138:        register char *to,
        !           139:        register const char *from,
        !           140:        register unsigned long count)
        !           141: {
        !           142:        register char *ret = to;
        !           143: 
        !           144:        while (count != 0) {
        !           145:                count--;
        !           146:                if ((*to++ = *from++) == '\0')
        !           147:                        break;
        !           148:        }
        !           149: 
        !           150:        while (count != 0) {
        !           151:                *to++ = '\0';
        !           152:                count--;
        !           153:        }
        !           154: 
        !           155:        return ret;
        !           156: }
        !           157: 
        !           158: /*
        !           159:  * Abstract:
        !           160:  *     strlen returns the number of characters in "string" preceeding 
        !           161:  *     the terminating null character.
        !           162:  */
        !           163: 
        !           164: unsigned long
        !           165: strlen(
        !           166:        register const char *string)
        !           167: {
        !           168:        register const char *ret = string;
        !           169: 
        !           170:        while (*string++ != '\0')
        !           171:                continue;
        !           172: 
        !           173:        return string - 1 - ret;
        !           174: }

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