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Diffstat (limited to 'kern/strings.c')
| -rw-r--r-- | kern/strings.c | 174 |
1 files changed, 174 insertions, 0 deletions
diff --git a/kern/strings.c b/kern/strings.c new file mode 100644 index 0000000..89563cd --- /dev/null +++ b/kern/strings.c @@ -0,0 +1,174 @@ +/* + * 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. + */ +/* + * 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 in the 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; + + do { + a = *s1++; + b = *s2++; + if (a != b) + return a-b; /* includes case when + 'a' is zero and 'b' is not zero + or vice versa */ + } while (a != '\0'); + + return 0; /* both are zero */ +} + + +/* + * 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 != 0) { + a = *s1++; + b = *s2++; + if (a != b) + return a-b; /* includes case when + 'a' is zero and 'b' is not zero + or vice versa */ + if (a == '\0') + return 0; /* both are zero */ + n--; + } + + return 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++) != '\0') + continue; + + 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) { + count--; + if ((*to++ = *from++) == '\0') + break; + } + + while (count != 0) { + *to++ = '\0'; + count--; + } + + 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++ != '\0') + continue; + + return string - 1 - ret; +} |