1 /*********************************************************************** 2 * * 3 * This software is part of the ast package * 4 * Copyright (c) 1985-2007 AT&T Knowledge Ventures * 5 * and is licensed under the * 6 * Common Public License, Version 1.0 * 7 * by AT&T Knowledge Ventures * 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22 #include "sfhdr.h" 23 24 /* Safe access to the internal stream buffer. 25 ** This function is obsolete.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 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