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att
GitHub Repository: att/ast
 Path: blob/master/src/lib/libcmd/revlib.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) 1992-2011 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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*                  David Korn <[email protected]>                   *

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*                                                                      *

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

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#pragma prototyped

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/*

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 * common support for tail and rev

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 */

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#include	<cmd.h>

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#include	<rev.h>

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#define BUFSIZE			SF_BUFSIZE

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#define rounddown(n,size)	(((n)-1)&~((size)-1))

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/*

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 * copy the lines starting at offset <start> from in <in> to <out>

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 * in reverse order

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 */

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int rev_line(Sfio_t *in, Sfio_t *out, off_t start)

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{

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	register char *cp, *cpold;

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	register int n, nleft=0;

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	char buff[BUFSIZE];

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	off_t offset;

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	if(sfseek(in,(off_t)0,SEEK_CUR) < 0)

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	{

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		Sfio_t *tmp = sftmp(4*SF_BUFSIZE);

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		if(!tmp)

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			return(-1);

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		if(start>0 && sfmove(in, (Sfio_t*)0, start, -1) != start)

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			return(-1);

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		if(sfmove(in, tmp, SF_UNBOUND, -1) < 0 || !sfeof(in) || sferror(tmp))

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			return(-1);

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		in = tmp;

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		start=0;

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	}

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	if((offset = sfseek(in,(off_t)0,SEEK_END)) <= start)

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		return(0);

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	offset = rounddown(offset,BUFSIZE);

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	while(1)

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	{

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		n = BUFSIZE;

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		if(offset < start)

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		{

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			n -= (start-offset);

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			offset = start;

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		}

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		sfseek(in, offset, SEEK_SET);

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		if((n=sfread(in, buff, n)) <=0)

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			break;

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		cp = buff+n;

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		n = *buff;

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		*buff = '\n';

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		while(1)

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		{

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			cpold = cp;

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			if(nleft==0)

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				cp--;

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			if(cp==buff)

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			{

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				nleft= 1;

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				break;

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			}

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			while(*--cp != '\n');

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			if(cp==buff && n!='\n')

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			{

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				*cp = n;

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				nleft += cpold-cp;

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				break;

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			}

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			else

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				cp++;

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			if(sfwrite(out,cp,cpold-cp) < 0)

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				return(-1);

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			if(nleft)

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			{

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				if(nleft==1)

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					sfputc(out,'\n');

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				else if(sfmove(in,out,nleft,-1) != nleft)

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					return(-1);

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				nleft = 0;

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			}

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		}

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		if(offset <= start)

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			break;

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		offset -= BUFSIZE;

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	}

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	if(nleft)

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	{

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		sfseek(in, start, SEEK_SET);

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		if(sfmove(in,out,nleft,-1) != nleft)

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			return(-1);

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	}

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	return(0);

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}

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