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Annotation of prex-old/usr/lib/libc/stdio/ungetc.c, Revision 1.1.1.1

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: }