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 /* Read n bytes from a stream into a buffer
25 **
26 ** Written by Kiem-Phong Vo.
27 */
28
29 #if __STD_C
sfread(Sfio_t * f,Void_t * buf,size_t n)30 ssize_t sfread(Sfio_t* f, Void_t* buf, size_t n)
31 #else
32 ssize_t sfread(f,buf,n)
33 Sfio_t* f; /* read from this stream. */
34 Void_t* buf; /* buffer to read into */
35 size_t n; /* number of bytes to be read. */
36 #endif
37 {
38 reg uchar *s, *begs;
39 reg ssize_t r;
40 reg int local, justseek;
41 SFMTXDECL(f);
42
43 SFMTXENTER(f, (ssize_t)(-1));
44
45 GETLOCAL(f,local);
46 justseek = f->bits&SF_JUSTSEEK; f->bits &= ~SF_JUSTSEEK;
47
48 if(!buf)
49 SFMTXRETURN(f, (ssize_t)(n == 0 ? 0 : -1) );
50
51 /* release peek lock */
52 if(f->mode&SF_PEEK)
53 { if(!(f->mode&SF_READ) )
54 SFMTXRETURN(f, (ssize_t)(-1));
55
56 if(f->mode&SF_GETR)
57 { if(((uchar*)buf + f->val) != f->next &&
58 (!f->rsrv || f->rsrv->data != (uchar*)buf) )
59 SFMTXRETURN(f, (ssize_t)(-1));
60 f->mode &= ~SF_PEEK;
61 SFMTXRETURN(f, 0);
62 }
63 else
64 { if((uchar*)buf != f->next)
65 SFMTXRETURN(f, (ssize_t)(-1));
66 f->mode &= ~SF_PEEK;
67 if(f->mode&SF_PKRD)
68 { /* actually read the data now */
69 f->mode &= ~SF_PKRD;
70 if(n > 0)
71 n = (r = sysreadf(f->file,f->data,n)) < 0 ? 0 : r;
72 f->endb = f->data+n;
73 f->here += n;
74 }
75 f->next += n;
76 f->endr = f->endb;
77 SFMTXRETURN(f, n);
78 }
79 }
80
81 s = begs = (uchar*)buf;
82 for(;; f->mode &= ~SF_LOCK)
83 { /* check stream mode */
84 if(SFMODE(f,local) != SF_READ && _sfmode(f,SF_READ,local) < 0)
85 { n = s > begs ? s-begs : (size_t)(-1);
86 SFMTXRETURN(f, (ssize_t)n);
87 }
88
89 SFLOCK(f,local);
90
91 if((r = f->endb - f->next) > 0) /* has buffered data */
92 { if(r > (ssize_t)n)
93 r = (ssize_t)n;
94 if(s != f->next)
95 memcpy(s, f->next, r);
96 f->next += r;
97 s += r;
98 n -= r;
99 }
100
101 if(n <= 0) /* all done */
102 break;
103
104 if(!(f->flags&SF_STRING) && !(f->bits&SF_MMAP) )
105 { f->next = f->endb = f->data;
106
107 /* exact IO is desirable for these cases */
108 if(SFDIRECT(f,n) ||
109 ((f->flags&SF_SHARE) && f->extent < 0) )
110 r = (ssize_t)n;
111 else if(justseek && n <= f->iosz && f->iosz <= f->size)
112 r = f->iosz; /* limit buffering */
113 else r = f->size; /* full buffering */
114
115 /* if read almost full size, then just do it direct */
116 if(r > (ssize_t)n && (r - r/8) <= (ssize_t)n)
117 r = (ssize_t)n;
118
119 /* read directly to user's buffer */
120 if(r == (ssize_t)n && (r = SFRD(f,s,r,f->disc)) >= 0)
121 { s += r;
122 n -= r;
123 if(r == 0 || n == 0) /* eof or eob */
124 break;
125 }
126 else goto do_filbuf;
127 }
128 else
129 { do_filbuf:
130 if(justseek)
131 f->bits |= SF_JUSTSEEK;
132 if(SFFILBUF(f,-1) <= 0)
133 break;
134 }
135 }
136
137 SFOPEN(f,local);
138 r = s-begs;
139 SFMTXRETURN(f, r);
140 }
141