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 * Eclipse Public License, Version 1.0 *
7 * by AT&T Intellectual Property *
8 * *
9 * A copy of the License is available at *
10 * http://www.eclipse.org/org/documents/epl-v10.html *
11 * (with md5 checksum b35adb5213ca9657e911e9befb180842) *
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 /* Fill the buffer of a stream with data.
25 ** If n < 0, sffilbuf() attempts to fill the buffer if it's empty.
26 ** If n == 0, if the buffer is not empty, just return the first byte;
27 ** otherwise fill the buffer and return the first byte.
28 ** If n > 0, even if the buffer is not empty, try a read to get as
29 ** close to n as possible. n is reset to -1 if stack pops.
30 **
31 ** Written by Kiem-Phong Vo
32 */
33
34 #if __STD_C
_sffilbuf(Sfio_t * f,reg int n)35 int _sffilbuf(Sfio_t* f, reg int n)
36 #else
37 int _sffilbuf(f,n)
38 Sfio_t* f; /* fill the read buffer of this stream */
39 reg int n; /* see above */
40 #endif
41 {
42 reg ssize_t r;
43 reg int first, local, rcrv, rc, justseek;
44 SFMTXDECL(f); /* declare a local stream variable for multithreading */
45
46 SFMTXENTER(f,-1);
47
48 GETLOCAL(f,local);
49
50 /* any peek data must be preserved across stacked streams */
51 rcrv = f->mode&(SF_RC|SF_RV|SF_LOCK);
52 rc = f->getr;
53
54 justseek = f->bits&SF_JUSTSEEK; f->bits &= ~SF_JUSTSEEK;
55
56 for(first = 1;; first = 0, (f->mode &= ~SF_LOCK) )
57 { /* check mode */
58 if(SFMODE(f,local) != SF_READ && _sfmode(f,SF_READ,local) < 0)
59 SFMTXRETURN(f,-1);
60 SFLOCK(f,local);
61
62 /* current extent of available data */
63 if((r = f->endb-f->next) > 0)
64 { /* on first iteration, n is amount beyond current buffer;
65 afterward, n is the exact amount requested */
66 if((first && n <= 0) || (!first && n <= r) ||
67 (f->flags&SF_STRING))
68 break;
69
70 /* try shifting left to make room for new data */
71 if(!(f->bits&SF_MMAP) && f->next > f->data &&
72 n > (f->size - (f->endb-f->data)) )
73 { ssize_t s = r;
74
75 /* try to maintain block alignment */
76 if(f->blksz > 0 && (f->here%f->blksz) == 0 )
77 { s = ((r + f->blksz-1)/f->blksz)*f->blksz;
78 if(s+n > f->size)
79 s = r;
80 }
81
82 memmove(f->data, f->endb-s, s);
83 f->next = f->data + (s-r);
84 f->endb = f->data + s;
85 }
86 }
87 else if(!(f->flags&SF_STRING) && !(f->bits&SF_MMAP) )
88 f->next = f->endb = f->endr = f->data;
89
90 if(f->bits&SF_MMAP)
91 r = n > 0 ? n : f->size;
92 else if(!(f->flags&SF_STRING) )
93 { r = f->size - (f->endb - f->data); /* available buffer */
94 if(n > 0)
95 { if(r > n && f->extent < 0 && (f->flags&SF_SHARE) )
96 r = n; /* read only as much as requested */
97 else if(justseek && n <= f->iosz && f->iosz <= f->size)
98 r = f->iosz; /* limit buffer filling */
99 }
100 }
101
102 /* SFRD takes care of discipline read and stack popping */
103 f->mode |= rcrv;
104 f->getr = rc;
105 if((r = SFRD(f,f->endb,r,f->disc)) >= 0)
106 { r = f->endb - f->next;
107 break;
108 }
109 }
110
111 SFOPEN(f,local);
112
113 rcrv = (n == 0) ? (r > 0 ? (int)(*f->next++) : EOF) : (int)r;
114
115 SFMTXRETURN(f,rcrv);
116 }
117