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Diffstat (limited to 'kern/strings.c')
| -rw-r--r-- | kern/strings.c | 275 |
1 files changed, 275 insertions, 0 deletions
diff --git a/kern/strings.c b/kern/strings.c new file mode 100644 index 0000000..7e7fda0 --- /dev/null +++ b/kern/strings.c @@ -0,0 +1,275 @@ +/* + * 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 <string.h> + +#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 up to the length of s1. + */ + +int __attribute__ ((pure)) +strcmp( + const char *s1, + const char *s2) +{ + 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 __attribute__ ((pure)) +strncmp( + const char *s1, + const char *s2, + size_t n) +{ + 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( + char *to, + const char *from) +{ + 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( + char *to, + const char *from, + size_t count) +{ + 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" preceding + * the terminating null character. + */ + +size_t __attribute__ ((pure)) +strlen( + const char *string) +{ + const char *ret = string; + + while (*string++ != '\0') + continue; + + return string - 1 - ret; +} + +/* + * Abstract: + * strchr returns a pointer to the first occurrence of the character + * "c" in the string "s". If "c" is not found, return NULL. + */ +char * +strchr( + const char *s, + int c) +{ + while (*s != c) { + if (*s == '\0') { + return NULL; + } + + s++; + } + + return (char *)s; +} + +/* + * Abstract: + * strsep extracts tokens from strings. If "*sp" is NULL, return NULL + * and do nothing. Otherwise, find the first token in string "*sp". + * Tokens are delimited by characters in the string "delim". If no + * delimiter is found, the token is the entire string "*sp", and "*sp" + * is made NULL. Otherwise, overwrite the delimiter with a null byte, + * and make "*sp" point past it. + */ +char * +strsep( + char **sp, + const char *delim) +{ + const char *d; + char *s, *t; + + s = t = *sp; + + if (s == NULL) { + return NULL; + } + + for (;;) { + if (*s == '\0') { + *sp = NULL; + return t; + } + + d = delim; + + for (;;) { + if (*d == '\0') { + break; + } + + if (*d == *s) { + *s = '\0'; + *sp = s + 1; + return t; + } + + d++; + } + + s++; + } +} + +/* + * Abstract: + * strstr returns a pointer to the first occurrence of the substring + * "find" in the string "s". If no substring was found, return NULL. + */ +char * +strstr( + const char *s, + const char *find) +{ + size_t len; + + len = strlen(find); + + if (len == 0) { + return (char *)s; + } + + for (;;) { + if (*s == '\0') { + return NULL; + } + + if (strncmp(s, find, len) == 0) { + return (char *)s; + } + + s++; + } +} |