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32 * @(#)ungetc.c 8.2 (Berkeley) 11/3/93
33 * $FreeBSD: src/lib/libc/stdio/ungetc.c,v 1.18 2008/04/17 22:17:54 jhb Exp $
34 * $DragonFly: src/lib/libc/stdio/ungetc.c,v 1.8 2005/11/20 11:07:30 swildner Exp $
37 #include "namespace.h"
41 #include "un-namespace.h"
43 #include "libc_private.h"
44 #include "priv_stdio.h"
46 static int __submore(FILE *);
49 * Expand the ungetc buffer `in place'. That is, adjust fp->pub._p when
50 * the buffer moves, so that it points the same distance from the end,
51 * and move the bytes in the buffer around as necessary so that they
52 * are all at the end (stack-style).
60 if (fp->_ub._base == fp->_ubuf) {
62 * Get a new buffer (rather than expanding the old one).
64 if ((p = malloc((size_t)BUFSIZ)) == NULL)
67 fp->_ub._size = BUFSIZ;
68 p += BUFSIZ - sizeof(fp->_ubuf);
69 for (i = sizeof(fp->_ubuf); --i >= 0;)
75 p = realloc(fp->_ub._base, (size_t)(i << 1));
78 /* no overlap (hence can use memcpy) because we doubled the size */
79 memcpy((void *)(p + i), (void *)p, (size_t)i);
82 fp->_ub._size = i << 1;
90 ungetc(int c, FILE *fp)
98 ret = __ungetc(c, fp);
104 * Non-MT-safe version
107 __ungetc(int c, FILE *fp)
111 if ((fp->pub._flags & __SRD) == 0) {
113 * Not already reading: no good unless reading-and-writing.
114 * Otherwise, flush any current write stuff.
116 if ((fp->pub._flags & __SRW) == 0)
118 if (fp->pub._flags & __SWR) {
121 fp->pub._flags &= ~__SWR;
123 fp->pub._lbfsize = 0;
125 fp->pub._flags |= __SRD;
127 c = (unsigned char)c;
130 * If we are in the middle of ungetc'ing, just continue.
131 * This may require expanding the current ungetc buffer.
134 if (fp->pub._r >= fp->_ub._size && __submore(fp))
140 fp->pub._flags &= ~__SEOF;
143 * If we can handle this by simply backing up, do so,
144 * but never replace the original character.
145 * (This makes sscanf() work when scanning `const' data.)
147 if (fp->_bf._base != NULL && fp->pub._p > fp->_bf._base &&
148 fp->pub._p[-1] == c) {
155 * Create an ungetc buffer.
156 * Initially, we will use the `reserve' buffer.
158 fp->_ur = fp->pub._r;
159 fp->_up = fp->pub._p;
160 fp->_ub._base = fp->_ubuf;
161 fp->_ub._size = sizeof(fp->_ubuf);
162 fp->_ubuf[sizeof(fp->_ubuf) - 1] = c;
163 fp->pub._p = &fp->_ubuf[sizeof(fp->_ubuf) - 1];