FreeBSD/Linux Kernel Cross Reference
sys/kern/strings.c

     /* 
      * Mach Operating System
      * Copyright (c) 1993 Carnegie Mellon University
      * All Rights Reserved.
      * 
      * Permission to use, copy, modify and distribute this software and its
      * documentation is hereby granted, provided that both the copyright
      * notice and this permission notice appear in all copies of the
      * software, derivative works or modified versions, and any portions
     * thereof, and that both notices appear in supporting documentation.
     * 
     * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
     * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
     * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
     * 
     * Carnegie Mellon requests users of this software to return to
     * 
     *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
     *  School of Computer Science
     *  Carnegie Mellon University
     *  Pittsburgh PA 15213-3890
     * 
     * any improvements or extensions that they make and grant Carnegie Mellon
     * the rights to redistribute these changes.
     */
    /*
     * HISTORY
     * $Log:        strings.c,v $
     * Revision 2.2  93/03/09  10:55:36  danner
     *      Created from Bob's new code in libmach.  Added strncmp().
     *      ANSI-fied, prototypes the way GCC wants them (signed char* ??).
     *      [93/03/06            af]
     * 
     */
    /*
     *      File: strings.c
     *      Author: Robert V. Baron, Carnegie Mellon University
     *      Date:   ??/92
     *
     *      String functions.
     */
    
    #include <kern/strings.h>       /* make sure we sell the truth */
    
    #ifdef  strcpy
    #undef strcmp
    #undef strncmp
    #undef strcpy
    #undef strncpy
    #undef strlen
    #endif
    
    /*
     * Abstract:
     *      strcmp (s1, s2) compares the strings "s1" and "s2".
     *      It returns 0 if the strings are identical. It returns
     *      > 0 if the first character that differs into two strings
     *      is larger in s1 than in s2 or if s1 is longer than s2 and 
     *      the contents  are identical up to the length of s2.
     *      It returns < 0 if the first differing character is smaller 
     *      in s1 than in s2 or if s1 is shorter than s2 and the
     *      contents are identical upto the length of s1.
     */
    
    int
    strcmp(
            register const char *s1,
            register const char *s2)
    {
            register unsigned int a, b;
    
            while ( (a = *s1++), (b = *s2++), a && b) {
                    if (a != b)
                            return (a-b);
            }
    
            return a-b;
    }
    
    
    /*
     * Abstract:
     *      strncmp (s1, s2, n) compares the strings "s1" and "s2"
     *      in exactly the same way as strcmp does.  Except the
     *      comparison runs for at most "n" characters.
     */
    
    int
    strncmp(
            register const char *s1,
            register const char *s2,
            unsigned long n)
    {
            register unsigned int a, b;
    
            while ( n, (a = *s1++), (b = *s2++), a && b) {
                    if (a != b)
                            return (a-b);
                    n--;
           }
   
           return n ? a-b : 0;
   }
   
   
   /*
    * Abstract:
    *      strcpy copies the contents of the string "from" including 
    *      the null terminator to the string "to". A pointer to "to"
    *      is returned.
    */
   
   char *
   strcpy(
           register char *to,
           register const char *from)
   {
           register char *ret = to;
   
           while(*to++ = *from++);
   
           return ret;
   }
   
   /*
    * Abstract:
    *      strncpy copies "count" characters from the "from" string to
    *      the "to" string. If "from" contains less than "count" characters
    *      "to" will be padded with null characters until exactly "count"
    *      characters have been written. The return value is a pointer
    *      to the "to" string.
    */
   
   char *
   strncpy(
       register char *to,
       register const char *from,
       register unsigned long count)
   {
       register char *ret = to;
   
       while (count-- > 0 && (*to++ = *from++));
   
       while (count-- > 0) 
           *to++ = '\0';
   
       return ret;
   }
   
   /*
    * Abstract:
    *      strlen returns the number of characters in "string" preceeding 
    *      the terminating null character.
    */
   
   unsigned long
   strlen(
       register const char *string)
   {
       register const char *ret = string;
   
       while (*string++);
   
       return string - 1 - ret;
   
   }

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