/*
 * 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.
 *	strchr(s, c)		Find first occurance of c in s.
 *	bcopy(from, to, n)	Copy a block of memory.
 *	number(s)		Convert a string of digits to an integer.
 *	is_number(s)		Return true if s is a string of digits.
 *
 * Copyright (C) 1989 by Kenneth Almquist.  All rights reserved.
 * This file is part of ash, which is distributed under the terms specified
 * by the Ash General Public License.  See the file named LICENSE.
 */

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


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


/*
 * 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';
}


/*
 * strchr - find first occurrence of a character in a string.
 */

#ifndef SYS5
char *
mystrchr(s, charwanted)
      char const *s;
      register char charwanted;
      {
      register char const *scan;

      /*
       * The odd placement of the two tests is so NUL is findable.
       */
      for (scan = s ; *scan != charwanted ; )	/* ++ moved down for opt. */
            if (*scan++ == '\0')
                  return NULL;
      return (char *)scan;
}
#endif



/*
 * bcopy - copy bytes
 *
 * This routine was derived from code by Henry Spencer.
 */

void
mybcopy(src, dst, length)
      pointer dst;
      const pointer src;
      register int length;
      {
      register char *d = dst;
      register char *s = src;

      while (--length >= 0)
            *d++ = *s++;
}


/*
 * 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;
}