1 /***********************************************************************
2 * *
3 * This software is part of the ast package *
4 * Copyright (c) 1985-2010 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
sfoutput(Sfio_t * f,char * buf,size_t n)31 static ssize_t sfoutput(Sfio_t* f, char* buf, size_t n)
32 #else
33 static ssize_t sfoutput(f,buf,n)
34 Sfio_t* f;
35 char* buf;
36 size_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
sfwr(Sfio_t * f,const Void_t * buf,size_t n,Sfdisc_t * disc)125 ssize_t sfwr(Sfio_t* f, const Void_t* buf, size_t n, Sfdisc_t* disc)
126 #else
127 ssize_t sfwr(f,buf,n,disc)
128 Sfio_t* f;
129 Void_t* buf;
130 size_t n;
131 Sfdisc_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