Annotation of prex-old/usr/lib/libc/stdio/ungetc.c, Revision 1.1
1.1 ! nbrk 1: /*-
! 2: * Copyright (c) 1990, 1993
! 3: * The Regents of the University of California. All rights reserved.
! 4: *
! 5: * This code is derived from software contributed to Berkeley by
! 6: * Chris Torek.
! 7: *
! 8: * Redistribution and use in source and binary forms, with or without
! 9: * modification, are permitted provided that the following conditions
! 10: * are met:
! 11: * 1. Redistributions of source code must retain the above copyright
! 12: * notice, this list of conditions and the following disclaimer.
! 13: * 2. Redistributions in binary form must reproduce the above copyright
! 14: * notice, this list of conditions and the following disclaimer in the
! 15: * documentation and/or other materials provided with the distribution.
! 16: * 3. Neither the name of the University nor the names of its contributors
! 17: * may be used to endorse or promote products derived from this software
! 18: * without specific prior written permission.
! 19: *
! 20: * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
! 21: * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
! 22: * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
! 23: * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
! 24: * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
! 25: * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
! 26: * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
! 27: * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
! 28: * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
! 29: * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
! 30: * SUCH DAMAGE.
! 31: */
! 32:
! 33: #include <stdio.h>
! 34: #include <stdlib.h>
! 35: #include <string.h>
! 36: #include "local.h"
! 37:
! 38: int
! 39: ungetc(c, fp)
! 40: int c;
! 41: FILE *fp;
! 42: {
! 43: if (c == EOF)
! 44: return (EOF);
! 45: if (!__sdidinit)
! 46: __sinit();
! 47: if ((fp->_flags & __SRD) == 0) {
! 48: /*
! 49: * Not already reading: no good unless reading-and-writing.
! 50: * Otherwise, flush any current write stuff.
! 51: */
! 52: if ((fp->_flags & __SRW) == 0)
! 53: return (EOF);
! 54: if (fp->_flags & __SWR) {
! 55: if (__sflush(fp))
! 56: return (EOF);
! 57: fp->_flags &= ~__SWR;
! 58: fp->_w = 0;
! 59: }
! 60: fp->_flags |= __SRD;
! 61: }
! 62: c = (unsigned char)c;
! 63:
! 64: /*
! 65: * If we are in the middle of ungetc'ing, just continue.
! 66: */
! 67: if (HASUB(fp)) {
! 68: if (fp->_r >= fp->_ub._size)
! 69: return (EOF);
! 70: *--fp->_p = c;
! 71: fp->_r++;
! 72: return (c);
! 73: }
! 74: fp->_flags &= ~__SEOF;
! 75:
! 76: /*
! 77: * If we can handle this by simply backing up, do so,
! 78: * but never replace the original character.
! 79: * (This makes sscanf() work when scanning `const' data.)
! 80: */
! 81: if (fp->_bf._base != NULL && fp->_p > fp->_bf._base &&
! 82: fp->_p[-1] == c) {
! 83: fp->_p--;
! 84: fp->_r++;
! 85: return (c);
! 86: }
! 87:
! 88: /*
! 89: * Create an ungetc buffer.
! 90: * we will use the `reserve' buffer.
! 91: */
! 92: fp->_ur = fp->_r;
! 93: fp->_up = fp->_p;
! 94: fp->_ub._base = fp->_ubuf;
! 95: fp->_ub._size = sizeof(fp->_ubuf);
! 96: fp->_ubuf[sizeof(fp->_ubuf) - 1] = c;
! 97: fp->_p = &fp->_ubuf[sizeof(fp->_ubuf) - 1];
! 98: fp->_r = 1;
! 99: return (c);
! 100: }
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