glibc/sysdeps/i386/strtok.S

/* strtok (str, delim) -- Return next DELIM separated token from STR.
For Intel 80x86, x>=3.
Copyright (C) 1996 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996.

The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.

The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Library General Public License for more details.

You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB.  If
not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.  */

#include <sysdep.h>

/* This file can be used for three variants of the strtok function:

   strtok:
	INPUT PARAMETER:
	str		(sp + 4)
	delim		(sp + 8)

   strtok_r:
	INPUT PARAMETER:
	str		(sp + 4)
	delim		(sp + 8)
	save_ptr	(sp + 12)

   We do a common implementation here.  */

#ifndef USE_AS_STRTOK_R
	.bss
	.local save_ptr
	ASM_TYPE_DIRECTIVE (save_ptr, @object)
	.size save_ptr, 4
save_ptr:
	.space 4

#define FUNCTION strtok
#endif

	.text

ENTRY (FUNCTION)

	movl 4(%esp), %edx		/* Get start of string.  */
	movl 8(%esp), %eax		/* Get start of delimiter set.  */

#if !defined (USE_AS_STRTOK_R) && defined (PIC)
	pushl %ebx			/* Save PIC register.  */
	call Lhere
Lhere:	popl %ebx
	addl $_GLOBAL_OFFSET_TABLE_+[.-Lhere], %ebx
#endif

	/* If the pointer is NULL we have to use the stored value of
	   the last run.  */
	cmpl $0, %edx
	jne L0

#ifdef USE_AS_STRTOK_R
	/* The value is stored in the third argument.  */
	movl 12(%esp), %edx
	movl (%edx), %edx
#else
	/* The value is in the local variable defined above.  But
	   we have to take care for PIC code.  */
# ifndef PIC
	movl save_ptr, %edx
# else
	movl save_ptr@GOTOFF(%ebx), %edx
# endif
#endif

L0:
	/* First we create a table with flags for all possible characters.
	   For the ASCII (7bit/8bit) or ISO-8859-X character sets which are
	   supported by the C string functions we have 256 characters.
	   Before inserting marks for the stop characters we clear the whole
	   table.  The unrolled form is much faster than a loop.  */
	xorl %ecx, %ecx		/* %ecx = 0 !!! */

	pushl %ecx		/* make a 256 bytes long block filled with 0 */
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl %ecx
	pushl $0		/* These immediate values make the label 2 */
	pushl $0		/* to be aligned on a 16 byte boundary to */
	pushl $0		/* get a better performance of the loop.  */
	pushl $0
	pushl $0
	pushl $0

/* For understanding the following code remember that %ecx == 0 now.
   Although all the following instruction only modify %cl we always
   have a correct zero-extended 32-bit value in %ecx.  */

L2:	movb (%eax), %cl	/* get byte from stopset */
	testb %cl, %cl		/* is NUL char? */
	jz L1			/* yes => start compare loop */
	movb %cl, (%esp,%ecx)	/* set corresponding byte in stopset table */

	movb 1(%eax), %cl	/* get byte from stopset */
	testb $0xff, %cl	/* is NUL char? */
	jz L1			/* yes => start compare loop */
	movb %cl, (%esp,%ecx)	/* set corresponding byte in stopset table */

	movb 2(%eax), %cl	/* get byte from stopset */
	testb $0xff, %cl	/* is NUL char? */
	jz L1			/* yes => start compare loop */
	movb %cl, (%esp,%ecx)	/* set corresponding byte in stopset table */

	movb 3(%eax), %cl	/* get byte from stopset */
	addl $4, %eax		/* increment stopset pointer */
	movb %cl, (%esp,%ecx)	/* set corresponding byte in stopset table */
	testb $0xff, %cl	/* is NUL char? */
	jnz L2			/* no => process next dword from stopset */

L1:	leal -4(%edx), %eax	/* prepare loop */

	/* We use a neat trick for the following loop.  Normally we would
	   have to test for two termination conditions
	   1. a character in the stopset was found
	   and
	   2. the end of the string was found
	   As a sign that the character is in the stopset we store its
	   value in the table.  The value of NUL is NUL so the loop
	   terminates for NUL in every case.  */

L3:	addl $4, %eax		/* adjust pointer for full loop round */

	movb (%eax), %cl	/* get byte from string */
	testb %cl, (%esp,%ecx)	/* is it contained in stopset? */
	jz L4			/* no => start of token */

	movb 1(%eax), %cl	/* get byte from string */
	testb %cl, (%esp,%ecx)	/* is it contained in stopset? */
	jz L5			/* no => start of token */

	movb 2(%eax), %cl	/* get byte from string */
	testb %cl, (%esp,%ecx)	/* is it contained in stopset? */
	jz L6			/* no => start of token */

	movb 3(%eax), %cl	/* get byte from string */
	testb %cl, (%esp,%ecx)	/* is it contained in stopset? */
	jnz L3			/* yes => start of loop */

	incl %eax		/* adjust pointer */
L6:	incl %eax
L5:	incl %eax

	/* Now we have to terminate the string.  */

L4:	leal -4(%eax), %edx	/* We use %EDX for the next run.  */

L7:	addl $4, %edx		/* adjust pointer for full loop round */

	movb (%edx), %cl	/* get byte from string */
	cmpb %cl, (%esp,%ecx)	/* is it contained in skipset? */
	je L8			/* yes => return */

	movb 1(%edx), %cl	/* get byte from string */
	cmpb %cl, (%esp,%ecx)	/* is it contained in skipset? */
	je L9			/* yes => return */

	movb 2(%edx), %cl	/* get byte from string */
	cmpb %cl, (%esp,%ecx)	/* is it contained in skipset? */
	je L10			/* yes => return */

	movb 3(%edx), %cl	/* get byte from string */
	cmpb %cl, (%esp,%ecx)	/* is it contained in skipset? */
	jne L7			/* no => start loop again */

	incl %edx		/* adjust pointer */
L10:	incl %edx
L9:	incl %edx

L8:	/* Remove the stopset table.  */
	addl $256, %esp

	cmpl %eax, %edx
	je LreturnNULL		/* There was no token anymore.  */

	movb $0, (%edx)		/* Terminate string.  */

	/* Are we at end of string?  */
	cmpb $0, %cl
	je L11

	incl %edx
L11:

	/* Store the pointer to the next character.  */
#ifdef USE_AS_STRTOK_R
	movl 12(%esp), %ecx
	movl %edx, (%ecx)
#else
# ifndef PIC
	movl %edx, save_ptr
# else
	movl %edx, save_ptr@GOTOFF(%ebx)
	popl %ebx
# endif
#endif
	ret

LreturnNULL:
	xorl %eax, %eax

	/* Store current pointer for next round.  */
#ifdef USE_AS_STRTOK_R
	movl 12(%esp), %ecx
	movl %edx, (%ecx)
#else
# ifndef PIC
	movl %edx, save_ptr
# else
	movl %edx, save_ptr@GOTOFF(%ebx)
	popl %ebx
# endif
#endif
	ret
END (FUNCTION)