1*46108Sbostic /*- 2*46108Sbostic * Copyright (c) 1990 The Regents of the University of California. 3*46108Sbostic * All rights reserved. 4*46108Sbostic * 5*46108Sbostic * This code is derived from software contributed to Berkeley by 6*46108Sbostic * Chris Torek. 7*46108Sbostic * 8*46108Sbostic * %sccs.include.redist.c% 9*46108Sbostic */ 10*46108Sbostic 1126665Sdonn #if defined(LIBC_SCCS) && !defined(lint) 12*46108Sbostic static char sccsid[] = "@(#)ungetc.c 5.4 (Berkeley) 01/20/91"; 13*46108Sbostic #endif /* LIBC_SCCS and not lint */ 1415084Ssam 152037Swnj #include <stdio.h> 16*46108Sbostic #include <stdlib.h> 17*46108Sbostic #include <string.h> 18*46108Sbostic #include "local.h" 192037Swnj 20*46108Sbostic /* 21*46108Sbostic * Expand the ungetc buffer `in place'. That is, adjust fp->_p when 22*46108Sbostic * the buffer moves, so that it points the same distance from the end, 23*46108Sbostic * and move the bytes in the buffer around as necessary so that they 24*46108Sbostic * are all at the end (stack-style). 25*46108Sbostic */ 26*46108Sbostic static 27*46108Sbostic __submore(fp) 28*46108Sbostic register FILE *fp; 292037Swnj { 30*46108Sbostic register int i; 31*46108Sbostic register unsigned char *p; 32*46108Sbostic 33*46108Sbostic if (fp->_ub._base == fp->_ubuf) { 34*46108Sbostic /* 35*46108Sbostic * Get a new buffer (rather than expanding the old one). 36*46108Sbostic */ 37*46108Sbostic if ((p = malloc((size_t)BUFSIZ)) == NULL) 38*46108Sbostic return (EOF); 39*46108Sbostic fp->_ub._base = p; 40*46108Sbostic fp->_ub._size = BUFSIZ; 41*46108Sbostic p += BUFSIZ - sizeof(fp->_ubuf); 42*46108Sbostic for (i = sizeof(fp->_ubuf); --i >= 0;) 43*46108Sbostic p[i] = fp->_ubuf[i]; 44*46108Sbostic fp->_p = p; 45*46108Sbostic return (0); 46*46108Sbostic } 47*46108Sbostic i = fp->_ub._size; 48*46108Sbostic p = realloc(fp->_ub._base, i << 1); 49*46108Sbostic if (p == NULL) 5017951Sserge return (EOF); 51*46108Sbostic (void) memcpy((void *)(p + i), (void *)p, (size_t)i); 52*46108Sbostic fp->_p = p + i; 53*46108Sbostic fp->_ub._base = p; 54*46108Sbostic fp->_ub._size = i << 1; 55*46108Sbostic return (0); 56*46108Sbostic } 5717951Sserge 58*46108Sbostic ungetc(c, fp) 59*46108Sbostic int c; 60*46108Sbostic register FILE *fp; 61*46108Sbostic { 62*46108Sbostic if (c == EOF) 63*46108Sbostic return (EOF); 64*46108Sbostic if (!__sdidinit) 65*46108Sbostic __sinit(); 66*46108Sbostic if ((fp->_flags & __SRD) == 0) { 67*46108Sbostic /* 68*46108Sbostic * Not already reading: no good unless reading-and-writing. 69*46108Sbostic * Otherwise, flush any current write stuff. 70*46108Sbostic */ 71*46108Sbostic if ((fp->_flags & __SRW) == 0) 7226938Sbloom return (EOF); 73*46108Sbostic if (fp->_flags & __SWR) { 74*46108Sbostic if (fflush(fp)) 75*46108Sbostic return (EOF); 76*46108Sbostic fp->_flags &= ~__SWR; 77*46108Sbostic fp->_w = 0; 78*46108Sbostic fp->_lbfsize = 0; 79*46108Sbostic } 80*46108Sbostic fp->_flags |= __SRD; 81*46108Sbostic } 82*46108Sbostic c = (unsigned char)c; 8317951Sserge 84*46108Sbostic /* 85*46108Sbostic * If we are in the middle of ungetc'ing, just continue. 86*46108Sbostic * This may require expanding the current ungetc buffer. 87*46108Sbostic */ 88*46108Sbostic if (HASUB(fp)) { 89*46108Sbostic if (fp->_r >= fp->_ub._size && __submore(fp)) 90*46108Sbostic return (EOF); 91*46108Sbostic *--fp->_p = c; 92*46108Sbostic fp->_r++; 93*46108Sbostic return (c); 94*46108Sbostic } 9517951Sserge 96*46108Sbostic /* 97*46108Sbostic * If we can handle this by simply backing up, do so, 98*46108Sbostic * but never replace the original character. 99*46108Sbostic * (This makes sscanf() work when scanning `const' data.) 100*46108Sbostic */ 101*46108Sbostic if (fp->_bf._base != NULL && fp->_p > fp->_bf._base && 102*46108Sbostic fp->_p[-1] == c) { 103*46108Sbostic fp->_p--; 104*46108Sbostic fp->_r++; 105*46108Sbostic return (c); 106*46108Sbostic } 107*46108Sbostic 108*46108Sbostic /* 109*46108Sbostic * Create an ungetc buffer. 110*46108Sbostic * Initially, we will use the `reserve' buffer. 111*46108Sbostic */ 112*46108Sbostic fp->_ur = fp->_r; 113*46108Sbostic fp->_up = fp->_p; 114*46108Sbostic fp->_ub._base = fp->_ubuf; 115*46108Sbostic fp->_ub._size = sizeof(fp->_ubuf); 116*46108Sbostic fp->_ubuf[sizeof(fp->_ubuf) - 1] = c; 117*46108Sbostic fp->_p = &fp->_ubuf[sizeof(fp->_ubuf) - 1]; 118*46108Sbostic fp->_r = 1; 11915084Ssam return (c); 1202037Swnj } 121