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BSD 4.3tahoe

/*
 * Copyright (c) 1983 Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms are permitted
 * provided that the above copyright notice and this paragraph are
 * duplicated in all such forms and that any documentation,
 * advertising materials, and other materials related to such
 * distribution and use acknowledge that the software was developed
 * by the University of California, Berkeley.  The name of the
 * University may not be used to endorse or promote products derived
 * from this software without specific prior written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */

#if defined(LIBC_SCCS) && !defined(lint)
	.asciz "@(#)strncpy.s	5.5 (Berkeley) 6/27/88"
#endif /* LIBC_SCCS and not lint */

/*
 * Copy string s2 over top of string s1.
 * Truncate or null-pad to n bytes.
 *
 * char *
 * strncpy(s1, s2, n)
 *	char *s1, *s2;
 */
#include "DEFS.h"

ENTRY(strncpy, R6)
	movl	12(ap),r6	# r6 = n
	bleq	done		# n <= 0
	movl	4(ap),r3	# r3 = s1
	movl	8(ap),r1	# r1 = s2
1:
	movzwl	$65535,r2	# r2 = bytes in first chunk
	cmpl	r6,r2		# r2 = min(bytes in chunk, n);
	jgeq	2f
	movl	r6,r2
2:
	subl2	r2,r6		# update n
	locc	$0,r2,(r1)	# '\0' found?
	jneq	3f
	subl2	r2,r1		# back up pointer updated by locc
	movc3	r2,(r1),(r3)	# copy in next piece
	tstl	r6		# run out of space?
	jneq	1b
	jbr	done
3:				# copy up to '\0' logic
	addl2	r0,r6		# r6 = number of null-pad bytes
	subl2	r0,r2		# r2 = number of bytes to move
	subl2	r2,r1		# back up pointer updated by locc
	movc3	r2,(r1),(r3)	# copy in last piece
4:				# null-pad logic
	movzwl	$65535,r2	# r2 = bytes in first chunk
	cmpl	r6,r2		# r2 = min(bytes in chunk, n);
	jgeq	5f
	movl	r6,r2
5:
	subl2	r2,r6		# update n
	movc5	$0,(r3),$0,r2,(r3)# pad with '\0's
	tstl	r6		# finished padding?
	jneq	4b
done:
	movl	4(ap),r0	# return s1
	ret

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