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+/*
+ * 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;
+}