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git.proxmox.com Git - mirror_edk2.git/blob - StdLib/LibC/Stdio/ungetc.c
2 Implementation of ungetc as declared in <stdio.h>.
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7 distribution. The full text of the license may be found at
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13 Copyright (c) 1990, 1993
14 The Regents of the University of California. All rights reserved.
16 This code is derived from software contributed to Berkeley by
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25 notice, this list of conditions and the following disclaimer in the
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29 without specific prior written permission.
31 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
32 AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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34 ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE
35 LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
36 CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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41 POSSIBILITY OF SUCH DAMAGE.
43 NetBSD: ungetc.c,v 1.14 2003/08/07 16:43:34 agc Exp
44 ungetc.c 8.2 (Berkeley) 11/3/93
46 #include <LibConfig.h>
53 #include "reentrant.h"
56 static int __submore(FILE *);
58 * Expand the ungetc buffer `in place'. That is, adjust fp->_p when
59 * the buffer moves, so that it points the same distance from the end,
60 * and move the bytes in the buffer around as necessary so that they
61 * are all at the end (stack-style).
69 _DIAGASSERT(fp
!= NULL
);
75 if (_UB(fp
)._base
== fp
->_ubuf
) {
77 * Get a new buffer (rather than expanding the old one).
79 if ((p
= malloc((size_t)BUFSIZ
)) == NULL
)
82 _UB(fp
)._size
= BUFSIZ
;
83 p
+= BUFSIZ
- sizeof(fp
->_ubuf
);
84 for (i
= sizeof(fp
->_ubuf
); --i
>= 0;)
90 p
= realloc(_UB(fp
)._base
, (size_t)(i
<< 1));
93 /* no overlap (hence can use memcpy) because we doubled the size */
94 (void)memcpy((void *)(p
+ i
), (void *)p
, (size_t)i
);
97 _UB(fp
)._size
= i
<< 1;
102 ungetc(int c
, FILE *fp
)
104 _DIAGASSERT(fp
!= NULL
);
115 _SET_ORIENTATION(fp
, -1);
116 if ((fp
->_flags
& __SRD
) == 0) {
118 * Not already reading: no good unless reading-and-writing.
119 * Otherwise, flush any current write stuff.
121 if ((fp
->_flags
& __SRW
) == 0) {
125 if (fp
->_flags
& __SWR
) {
130 fp
->_flags
&= ~__SWR
;
136 c
= (unsigned char)c
;
139 * If we are in the middle of ungetc'ing, just continue.
140 * This may require expanding the current ungetc buffer.
143 if (fp
->_r
>= _UB(fp
)._size
&& __submore(fp
)) {
147 *--fp
->_p
= (unsigned char)c
;
152 fp
->_flags
&= ~__SEOF
;
155 * If we can handle this by simply backing up, do so,
156 * but never replace the original character.
157 * (This makes sscanf() work when scanning `const' data.)
159 if (fp
->_bf
._base
!= NULL
&& fp
->_p
> fp
->_bf
._base
&&
168 * Create an ungetc buffer.
169 * Initially, we will use the `reserve' buffer.
173 _UB(fp
)._base
= fp
->_ubuf
;
174 _UB(fp
)._size
= sizeof(fp
->_ubuf
);
175 fp
->_ubuf
[sizeof(fp
->_ubuf
) - 1] = (unsigned char)c
;
176 fp
->_p
= &fp
->_ubuf
[sizeof(fp
->_ubuf
) - 1];