1/***********************************************************************
2*                                                                      *
3*               This software is part of the ast package               *
4*          Copyright (c) 1985-2011 AT&T Intellectual Property          *
5*                      and is licensed under the                       *
6*                  Common Public License, Version 1.0                  *
7*                    by AT&T Intellectual Property                     *
8*                                                                      *
9*                A copy of the License is available at                 *
10*            http://www.opensource.org/licenses/cpl1.0.txt             *
11*         (with md5 checksum 059e8cd6165cb4c31e351f2b69388fd9)         *
12*                                                                      *
13*              Information and Software Systems Research               *
14*                            AT&T Research                             *
15*                           Florham Park NJ                            *
16*                                                                      *
17*                 Glenn Fowler <gsf@research.att.com>                  *
18*                  David Korn <dgk@research.att.com>                   *
19*                   Phong Vo <kpv@research.att.com>                    *
20*                                                                      *
21***********************************************************************/
22#include	"sfhdr.h"
23
24/*	Write with discipline.
25**
26**	Written by Kiem-Phong Vo.
27*/
28
29/* hole preserving writes */
30#if __STD_C
31static ssize_t sfoutput(Sfio_t* f, char* buf, size_t n)
32#else
33static ssize_t sfoutput(f,buf,n)
34Sfio_t*		f;
35char*		buf;
36size_t		n;
37#endif
38{	reg char	*sp, *wbuf, *endbuf;
39	reg ssize_t	s, w, wr;
40
41	s = w = 0;
42	wbuf = buf;
43	endbuf = buf+n;
44	while(n > 0)
45	{	if((ssize_t)n < _Sfpage) /* no hole possible */
46		{	buf += n;
47			s = n = 0;
48		}
49		else while((ssize_t)n >= _Sfpage)
50		{	/* see if a hole of 0's starts here */
51			sp = buf+1;
52			if(buf[0] == 0 && buf[_Sfpage-1] == 0)
53			{	/* check byte at a time until int-aligned */
54				while(((ulong)sp)%sizeof(int))
55				{	if(*sp != 0)
56						goto chk_hole;
57					sp += 1;
58				}
59
60				/* check using int to speed up */
61				while(sp < endbuf)
62				{	if(*((int*)sp) != 0)
63						goto chk_hole;
64					sp += sizeof(int);
65				}
66
67				/* check the remaining bytes */
68				if(sp > endbuf)
69				{	sp -= sizeof(int);
70					while(sp < endbuf)
71					{	if(*sp != 0)
72							goto chk_hole;
73						sp += 1;
74					}
75				}
76			}
77
78		chk_hole:
79			if((s = sp-buf) >= _Sfpage) /* found a hole */
80				break;
81
82			/* skip a dirty page */
83			n -= _Sfpage;
84			buf += _Sfpage;
85		}
86
87		/* write out current dirty pages */
88		if(buf > wbuf)
89		{	if((ssize_t)n < _Sfpage)
90			{	buf = endbuf;
91				n = s = 0;
92			}
93			if((wr = syswritef(f->file,wbuf,buf-wbuf)) > 0)
94			{	w += wr;
95				f->bits &= ~SF_HOLE;
96			}
97			if(wr != (buf-wbuf))
98				break;
99			wbuf = buf;
100		}
101
102		/* seek to a rounded boundary within the hole */
103		if(s >= _Sfpage)
104		{	s = (s/_Sfpage)*_Sfpage;
105			if(SFSK(f,(Sfoff_t)s,SEEK_CUR,NIL(Sfdisc_t*)) < 0)
106				break;
107			w += s;
108			n -= s;
109			wbuf = (buf += s);
110			f->bits |= SF_HOLE;
111
112			if(n > 0)
113			{	/* next page must be dirty */
114				s = (ssize_t)n <= _Sfpage ? 1 : _Sfpage;
115				buf += s;
116				n -= s;
117			}
118		}
119	}
120
121	return w > 0 ? w : -1;
122}
123
124#if __STD_C
125ssize_t sfwr(Sfio_t* f, const Void_t* buf, size_t n, Sfdisc_t* disc)
126#else
127ssize_t sfwr(f,buf,n,disc)
128Sfio_t*		f;
129Void_t*		buf;
130size_t		n;
131Sfdisc_t*	disc;
132#endif
133{
134	reg ssize_t	w;
135	reg Sfdisc_t*	dc;
136	reg int		local, oerrno;
137	SFMTXDECL(f);
138
139	SFMTXENTER(f,(ssize_t)(-1));
140
141	GETLOCAL(f,local);
142	if(!local && !(f->bits&SF_DCDOWN)) /* an external user's call */
143	{	if(f->mode != SF_WRITE && _sfmode(f,SF_WRITE,0) < 0 )
144			SFMTXRETURN(f, (ssize_t)(-1));
145		if(f->next > f->data && SFSYNC(f) < 0 )
146			SFMTXRETURN(f, (ssize_t)(-1));
147	}
148
149	for(;;)
150	{	/* stream locked by sfsetfd() */
151		if(!(f->flags&SF_STRING) && f->file < 0)
152			SFMTXRETURN(f,(ssize_t)0);
153
154		/* clear current error states */
155		f->flags &= ~(SF_EOF|SF_ERROR);
156
157		dc = disc;
158		if(f->flags&SF_STRING)	/* total required buffer */
159			w = n + (f->next - f->data);
160		else
161		{	/* warn that a write is about to happen */
162			SFDISC(f,dc,writef);
163			if(dc && dc->exceptf && (f->flags&SF_IOCHECK) )
164			{	reg int	rv;
165				if(local)
166					SETLOCAL(f);
167				if((rv = _sfexcept(f,SF_WRITE,n,dc)) > 0)
168					n = rv;
169				else if(rv < 0)
170				{	f->flags |= SF_ERROR;
171					SFMTXRETURN(f, rv);
172				}
173			}
174
175			if(f->extent >= 0)
176			{	/* make sure we are at the right place to write */
177				if(f->flags&SF_APPENDWR)
178				{	if(f->here != f->extent || (f->flags&SF_SHARE))
179					{	f->here = SFSK(f,(Sfoff_t)0,SEEK_END,dc);
180						f->extent = f->here;
181					}
182				}
183				else if((f->flags&SF_SHARE) && !(f->flags&SF_PUBLIC))
184					f->here = SFSK(f,f->here,SEEK_SET,dc);
185			}
186
187			oerrno = errno;
188			errno = 0;
189
190			if(dc && dc->writef)
191			{	SFDCWR(f,buf,n,dc,w);
192			}
193			else if(SFISNULL(f))
194				w = n;
195			else if(f->flags&SF_WHOLE)
196				goto do_write;
197			else if((ssize_t)n >= _Sfpage &&
198				!(f->flags&(SF_SHARE|SF_APPENDWR)) &&
199				f->here == f->extent && (f->here%_Sfpage) == 0)
200			{	if((w = sfoutput(f,(char*)buf,n)) <= 0)
201					goto do_write;
202			}
203			else
204			{
205			do_write:
206				if((w = syswritef(f->file,buf,n)) > 0)
207					f->bits &= ~SF_HOLE;
208			}
209
210			if(errno == 0)
211				errno = oerrno;
212
213			if(w > 0)
214			{	if(!(f->bits&SF_DCDOWN) )
215				{	if((f->flags&(SF_APPENDWR|SF_PUBLIC)) && f->extent >= 0 )
216						f->here = SFSK(f,(Sfoff_t)0,SEEK_CUR,dc);
217					else	f->here += w;
218					if(f->extent >= 0 && f->here > f->extent)
219						f->extent = f->here;
220				}
221
222				SFMTXRETURN(f, (ssize_t)w);
223			}
224		}
225
226		if(local)
227			SETLOCAL(f);
228		switch(_sfexcept(f,SF_WRITE,w,dc))
229		{
230		case SF_ECONT :
231			goto do_continue;
232		case SF_EDONE :
233			w = local ? 0 : w;
234			SFMTXRETURN(f, (ssize_t)w);
235		case SF_EDISC :
236			if(!local && !(f->flags&SF_STRING))
237				goto do_continue;
238			/* else fall thru */
239		case SF_ESTACK :
240			SFMTXRETURN(f, (ssize_t)(-1));
241		}
242
243	do_continue:
244		for(dc = f->disc; dc; dc = dc->disc)
245			if(dc == disc)
246				break;
247		disc = dc;
248	}
249}
250