1 /*********************************************************************** 2 * * 3 * This software is part of the ast package * 4 * Copyright (c) 1985-2008 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 /* 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 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); 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 memcpy(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