/*-
 * Copyright (c) 1991, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Kenneth Almquist.
 *
 * %sccs.include.redist.c%
 */

#ifndef lint
static char sccsid[] = "@(#)mystring.c	8.1 (Berkeley) 05/31/93";
#endif /* not lint */

/*
 * String functions.
 *
 *	equal(s1, s2)		Return true if strings are equal.
 *	scopy(from, to)		Copy a string.
 *	scopyn(from, to, n)	Like scopy, but checks for overflow.
 *	number(s)		Convert a string of digits to an integer.
 *	is_number(s)		Return true if s is a string of digits.
 */

#include "shell.h"
#include "syntax.h"
#include "error.h"
#include "mystring.h"


char nullstr[1];		/* zero length string */

/*
 * equal - #defined in mystring.h
 */

/*
 * scopy - #defined in mystring.h
 */


/*
 * scopyn - copy a string from "from" to "to", truncating the string
 *		if necessary.  "To" is always nul terminated, even if
 *		truncation is performed.  "Size" is the size of "to".
 */

void
scopyn(from, to, size)
	register char const *from;
	register char *to;
	register int size;
	{

	while (--size > 0) {
		if ((*to++ = *from++) == '\0')
			return;
	}
	*to = '\0';
}


/*
 * prefix -- see if pfx is a prefix of string.
 */

int
prefix(pfx, string)
	register char const *pfx;
	register char const *string;
	{
	while (*pfx) {
		if (*pfx++ != *string++)
			return 0;
	}
	return 1;
}


/*
 * Convert a string of digits to an integer, printing an error message on
 * failure.
 */

int
number(s)
	const char *s;
	{

	if (! is_number(s))
		error2("Illegal number", (char *)s);
	return atoi(s);
}



/*
 * Check for a valid number.  This should be elsewhere.
 */

int
is_number(p)
	register const char *p;
	{
	do {
		if (! is_digit(*p))
			return 0;
	} while (*++p != '\0');
	return 1;
}