diff options
Diffstat (limited to 'libc/stdio/ungetc.c')
| -rw-r--r-- | libc/stdio/ungetc.c | 141 |
1 files changed, 141 insertions, 0 deletions
diff --git a/libc/stdio/ungetc.c b/libc/stdio/ungetc.c new file mode 100644 index 0000000..fe05258 --- /dev/null +++ b/libc/stdio/ungetc.c @@ -0,0 +1,141 @@ +/* $OpenBSD: ungetc.c,v 1.9 2005/08/08 08:05:36 espie Exp $ */ +/*- + * Copyright (c) 1990, 1993 + * The Regents of the University of California. All rights reserved. + * + * This code is derived from software contributed to Berkeley by + * Chris Torek. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * 3. Neither the name of the University nor the names of its contributors + * may be used to endorse or promote products derived from this software + * without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + */ + +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include "local.h" + +static int __submore(FILE *); +/* + * Expand the ungetc buffer `in place'. That is, adjust fp->_p when + * the buffer moves, so that it points the same distance from the end, + * and move the bytes in the buffer around as necessary so that they + * are all at the end (stack-style). + */ +static int +__submore(FILE *fp) +{ + int i; + unsigned char *p; + + if (_UB(fp)._base == fp->_ubuf) { + /* + * Get a new buffer (rather than expanding the old one). + */ + if ((p = malloc((size_t)BUFSIZ)) == NULL) + return (EOF); + _UB(fp)._base = p; + _UB(fp)._size = BUFSIZ; + p += BUFSIZ - sizeof(fp->_ubuf); + for (i = sizeof(fp->_ubuf); --i >= 0;) + p[i] = fp->_ubuf[i]; + fp->_p = p; + return (0); + } + i = _UB(fp)._size; + p = realloc(_UB(fp)._base, i << 1); + if (p == NULL) + return (EOF); + /* no overlap (hence can use memcpy) because we doubled the size */ + (void)memcpy((void *)(p + i), (void *)p, (size_t)i); + fp->_p = p + i; + _UB(fp)._base = p; + _UB(fp)._size = i << 1; + return (0); +} + +int +ungetc(int c, FILE *fp) +{ + if (c == EOF) + return (EOF); + if (!__sdidinit) + __sinit(); + _SET_ORIENTATION(fp, -1); + if ((fp->_flags & __SRD) == 0) { + /* + * Not already reading: no good unless reading-and-writing. + * Otherwise, flush any current write stuff. + */ + if ((fp->_flags & __SRW) == 0) + return (EOF); + if (fp->_flags & __SWR) { + if (__sflush(fp)) + return (EOF); + fp->_flags &= ~__SWR; + fp->_w = 0; + fp->_lbfsize = 0; + } + fp->_flags |= __SRD; + } + c = (unsigned char)c; + + /* + * If we are in the middle of ungetc'ing, just continue. + * This may require expanding the current ungetc buffer. + */ + if (HASUB(fp)) { + if (fp->_r >= _UB(fp)._size && __submore(fp)) + return (EOF); + *--fp->_p = c; + fp->_r++; + return (c); + } + fp->_flags &= ~__SEOF; + + /* + * If we can handle this by simply backing up, do so, + * but never replace the original character. + * (This makes sscanf() work when scanning `const' data.) + */ + if (fp->_bf._base != NULL && fp->_p > fp->_bf._base && + fp->_p[-1] == c) { + fp->_p--; + fp->_r++; + return (c); + } + + /* + * Create an ungetc buffer. + * Initially, we will use the `reserve' buffer. + */ + fp->_ur = fp->_r; + fp->_up = fp->_p; + _UB(fp)._base = fp->_ubuf; + _UB(fp)._size = sizeof(fp->_ubuf); + fp->_ubuf[sizeof(fp->_ubuf) - 1] = c; + fp->_p = &fp->_ubuf[sizeof(fp->_ubuf) - 1]; + fp->_r = 1; + return (c); +} |