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 /* Safe access to the internal stream buffer.
25 ** This function is obsolete. sfreserve() should be used.
26 **
27 ** Written by Kiem-Phong Vo (06/27/90).
28 */
29
30 #if _BLD_sfio && defined(__EXPORT__)
31 #define extern __EXPORT__
32 #endif
33
34 #if __STD_C
sfpeek(reg Sfio_t * f,Void_t ** bp,reg size_t size)35 extern ssize_t sfpeek(reg Sfio_t* f, Void_t** bp, reg size_t size)
36 #else
37 extern ssize_t sfpeek(f,bp,size)
38 reg Sfio_t* f; /* file to peek */
39 Void_t** bp; /* start of data area */
40 reg size_t size; /* size of peek */
41 #endif
42 { reg ssize_t n, sz;
43 reg int mode;
44
45 /* query for the extent of the remainder of the buffer */
46 if((sz = size) == 0 || !bp)
47 { if(f->mode&SF_INIT)
48 (void)_sfmode(f,0,0);
49
50 if((f->flags&SF_RDWRSTR) == SF_RDWRSTR)
51 { SFSTRSIZE(f);
52 n = (f->data+f->here) - f->next;
53 }
54 else n = f->endb - f->next;
55
56 if(!bp)
57 return n;
58 else if(n > 0) /* size == 0 */
59 { *bp = (Void_t*)f->next;
60 return 0;
61 }
62 /* else fall down and fill buffer */
63 }
64
65 if(!(mode = f->flags&SF_READ) )
66 mode = SF_WRITE;
67 if((int)f->mode != mode && _sfmode(f,mode,0) < 0)
68 return -1;
69
70 *bp = sfreserve(f, sz <= 0 ? 0 : sz > f->size ? f->size : sz, 0);
71
72 if(*bp && sz >= 0)
73 return sz;
74
75 if((n = sfvalue(f)) > 0)
76 { *bp = (Void_t*)f->next;
77 if(sz < 0)
78 { f->mode |= SF_PEEK;
79 f->endr = f->endw = f->data;
80 }
81 else
82 { if(sz > n)
83 sz = n;
84 f->next += sz;
85 }
86 }
87
88 return (sz >= 0 && n >= sz) ? sz : n;
89 }
90