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att
GitHub Repository: att/ast
 Path: blob/master/src/lib/libcs/msgbuf.c
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/***********************************************************************

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*                                                                      *

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*               This software is part of the ast package               *

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*          Copyright (c) 1990-2011 AT&T Intellectual Property          *

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*                      and is licensed under the                       *

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*                 Eclipse Public License, Version 1.0                  *

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*                    by AT&T Intellectual Property                     *

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*                                                                      *

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*                A copy of the License is available at                 *

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*          http://www.eclipse.org/org/documents/epl-v10.html           *

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*         (with md5 checksum b35adb5213ca9657e911e9befb180842)         *

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*                                                                      *

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*              Information and Software Systems Research               *

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*                            AT&T Research                             *

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*                           Florham Park NJ                            *

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*                                                                      *

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*                 Glenn Fowler <[email protected]>                  *

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*                                                                      *

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***********************************************************************/

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#pragma prototyped

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/*

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 * system call message buffer support

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 */

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#include "msglib.h"

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/*

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 * get encoded unsigned long from buf

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 */

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unsigned long

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msggetu(char** buf, char* end)

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{

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	register int		c;

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	register unsigned char*	s;

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	register unsigned char*	e;

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	register unsigned long	v;

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	v = 0;

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	s = (unsigned char*)*buf;

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	e = (unsigned char*)end;

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	do

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	{

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		if (s >= e) return -1L;

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		c = *s++;

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		v = (v << 7) | (c & 0177);

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	} while (c & 0200);

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	*buf = (char*)s;

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	return v;

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}

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/*

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 * encode unsigned long into buf

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 */

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int

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msgputu(char** buf, char* end, register unsigned long v)

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{

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	register char*	s;

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	register char*	t;

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	register int	n;

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	char		tmp[2 * sizeof(unsigned long)];

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	s = t = &tmp[elementsof(tmp) - 1];

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	*t = v & 0177;

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	while((v >>= 7) > 0)

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		*--t = (v & 0177) | 0200;

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	n = s - t + 1;

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	if ((s = *buf) + n >= end)

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		return 0;

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	switch (n)

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	{

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	default: for (v = n - 7; v-- > 0;) *s++ = *t++;

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	case 7:	*s++ = *t++;

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	case 6:	*s++ = *t++;

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	case 5:	*s++ = *t++;

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	case 4:	*s++ = *t++;

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	case 3:	*s++ = *t++;

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	case 2:	*s++ = *t++;

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	case 1:	*s++ = *t++;

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	}

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	*buf = s;

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	return n;

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}

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/*

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 * copy <data,size> from buf

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 */

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size_t

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msggetz(char** buf, char* end, void* data, size_t size)

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{

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	register size_t	n;

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	register size_t	i;

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	i = end - *buf;

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	n = msggetu(buf, end);

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	if (n > i) n = i;

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	if (size > n) size = n;

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	if (size) memcpy(data, *buf, size);

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	*buf += n;

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	return n;

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}

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/*

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 * copy <data,size> to buf

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 */

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int

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msgputz(char** buf, char* end, void* data, size_t size)

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{

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	register char*	s;

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	register size_t	n;

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	s = *buf;

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	n = end - s;

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	if (n > size) n = size;

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	msgputu(buf, end, n);

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	if (n)

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	{

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		if (n > (end - *buf))

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		{

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			n = end - *buf;

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			*buf = s;

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			msgputu(buf, end, n);

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		}

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		memcpy(*buf, data, n);

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		*buf += n;

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	}

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	return *buf - s;

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}

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