1 /* Flushing buffers of a FILE stream.
2    Copyright (C) 2007-2021 Free Software Foundation, Inc.
3 
4    This file is free software: you can redistribute it and/or modify
5    it under the terms of the GNU Lesser General Public License as
6    published by the Free Software Foundation; either version 2.1 of the
7    License, or (at your option) any later version.
8 
9    This file is distributed in the hope that it will be useful,
10    but WITHOUT ANY WARRANTY; without even the implied warranty of
11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12    GNU Lesser General Public License for more details.
13 
14    You should have received a copy of the GNU Lesser General Public License
15    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
16 
17 #include <config.h>
18 
19 /* Specification.  */
20 #include <stdio.h>
21 
22 #if HAVE___FPURGE                   /* glibc >= 2.2, Haiku, Solaris >= 7, UnixWare >= 7.1.4.MP4, Cygwin >= 1.7.10, Android API >= 23, musl libc */
23 # if HAVE_STDIO_EXT_H
24 #  include <stdio_ext.h>
25 # endif
26 #endif
27 #include <stdlib.h>
28 
29 #include "stdio-impl.h"
30 
31 int
fpurge(FILE * fp)32 fpurge (FILE *fp)
33 {
34 #if HAVE___FPURGE                   /* glibc >= 2.2, Haiku, Solaris >= 7, UnixWare >= 7.1.4.MP4, Cygwin >= 1.7.10, Android API >= 23, musl libc */
35 
36   __fpurge (fp);
37   /* The __fpurge function does not have a return value.  */
38   return 0;
39 
40 #elif HAVE_FPURGE                   /* FreeBSD, NetBSD, OpenBSD, DragonFly, Mac OS X, Cygwin >= 1.7 */
41 
42   /* Call the system's fpurge function.  */
43 # undef fpurge
44 # if !HAVE_DECL_FPURGE
45   extern int fpurge (FILE *);
46 # endif
47   int result = fpurge (fp);
48 # if defined __sferror || defined __DragonFly__ || defined __ANDROID__
49   /* FreeBSD, NetBSD, OpenBSD, DragonFly, Mac OS X, Cygwin, Minix 3, Android */
50   if (result == 0)
51     /* Correct the invariants that fpurge broke.
52        <stdio.h> on BSD systems says:
53          "The following always hold: if _flags & __SRD, _w is 0."
54        If this invariant is not fulfilled and the stream is read-write but
55        currently reading, subsequent putc or fputc calls will write directly
56        into the buffer, although they shouldn't be allowed to.  */
57     if ((fp_->_flags & __SRD) != 0)
58       fp_->_w = 0;
59 # endif
60   return result;
61 
62 #else
63 
64   /* Most systems provide FILE as a struct and the necessary bitmask in
65      <stdio.h>, because they need it for implementing getc() and putc() as
66      fast macros.  */
67 # if defined _IO_EOF_SEEN || defined _IO_ftrylockfile || __GNU_LIBRARY__ == 1
68   /* GNU libc, BeOS, Haiku, Linux libc5 */
69   fp->_IO_read_end = fp->_IO_read_ptr;
70   fp->_IO_write_ptr = fp->_IO_write_base;
71   /* Avoid memory leak when there is an active ungetc buffer.  */
72   if (fp->_IO_save_base != NULL)
73     {
74       free (fp->_IO_save_base);
75       fp->_IO_save_base = NULL;
76     }
77   return 0;
78 # elif defined __sferror || defined __DragonFly__ || defined __ANDROID__
79   /* FreeBSD, NetBSD, OpenBSD, DragonFly, Mac OS X, Cygwin, Minix 3, Android */
80   fp_->_p = fp_->_bf._base;
81   fp_->_r = 0;
82   fp_->_w = ((fp_->_flags & (__SLBF | __SNBF | __SRD)) == 0 /* fully buffered and not currently reading? */
83              ? fp_->_bf._size
84              : 0);
85   /* Avoid memory leak when there is an active ungetc buffer.  */
86   if (fp_ub._base != NULL)
87     {
88       if (fp_ub._base != fp_->_ubuf)
89         free (fp_ub._base);
90       fp_ub._base = NULL;
91     }
92   return 0;
93 # elif defined __EMX__              /* emx+gcc */
94   fp->_ptr = fp->_buffer;
95   fp->_rcount = 0;
96   fp->_wcount = 0;
97   fp->_ungetc_count = 0;
98   return 0;
99 # elif defined __minix              /* Minix */
100   fp->_ptr = fp->_buf;
101   if (fp->_ptr != NULL)
102     fp->_count = 0;
103   return 0;
104 # elif defined _IOERR               /* AIX, HP-UX, IRIX, OSF/1, Solaris, OpenServer, UnixWare, mingw, MSVC, NonStop Kernel, OpenVMS */
105   fp_->_ptr = fp_->_base;
106   if (fp_->_ptr != NULL)
107     fp_->_cnt = 0;
108   return 0;
109 # elif defined __UCLIBC__           /* uClibc */
110 #  ifdef __STDIO_BUFFERS
111   if (fp->__modeflags & __FLAG_WRITING)
112     fp->__bufpos = fp->__bufstart;
113   else if (fp->__modeflags & (__FLAG_READONLY | __FLAG_READING))
114     fp->__bufpos = fp->__bufread;
115 #  endif
116   return 0;
117 # elif defined __QNX__              /* QNX */
118   fp->_Rback = fp->_Back + sizeof (fp->_Back);
119   fp->_Rsave = NULL;
120   if (fp->_Mode & 0x2000 /* _MWRITE */)
121     /* fp->_Buf <= fp->_Next <= fp->_Wend */
122     fp->_Next = fp->_Buf;
123   else
124     /* fp->_Buf <= fp->_Next <= fp->_Rend */
125     fp->_Rend = fp->_Next;
126   return 0;
127 # elif defined __MINT__             /* Atari FreeMiNT */
128   if (fp->__pushed_back)
129     {
130       fp->__bufp = fp->__pushback_bufp;
131       fp->__pushed_back = 0;
132     }
133   /* Preserve the current file position.  */
134   if (fp->__target != -1)
135     fp->__target += fp->__bufp - fp->__buffer;
136   fp->__bufp = fp->__buffer;
137   /* Nothing in the buffer, next getc is nontrivial.  */
138   fp->__get_limit = fp->__bufp;
139   /* Nothing in the buffer, next putc is nontrivial.  */
140   fp->__put_limit = fp->__buffer;
141   return 0;
142 # elif defined EPLAN9               /* Plan9 */
143   fp->rp = fp->wp = fp->lp = fp->buf;
144   return 0;
145 # else
146 #  error "Please port gnulib fpurge.c to your platform! Look at the definitions of fflush, setvbuf and ungetc on your system, then report this to bug-gnulib."
147 # endif
148 
149 #endif
150 }
151