Initial source

1 files changed, 174 insertions, 0 deletions

diff --git a/kern/strings.c b/kern/strings.c
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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;
+}