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[glibc.git] / stdio / memstream.c
blobfe2ce0a5726dbe9dee799acf499eb2cb5e65f0d2
1 /* Copyright (C) 1991, 92, 94, 95, 96, 97 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Library General Public License as
6 published by the Free Software Foundation; either version 2 of the
7 License, or (at your option) any later version.
9 The GNU C Library 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 GNU
12 Library General Public License for more details.
14 You should have received a copy of the GNU Library General Public
15 License along with the GNU C Library; see the file COPYING.LIB. If not,
16 write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
17 Boston, MA 02111-1307, USA. */
19 #include <stdio.h>
20 #include <stdlib.h>
21 #include <string.h>
22 #include <errno.h>
24 struct memstream_info
26 char **buffer;
27 size_t *bufsize;
30 /* Enlarge STREAM's buffer. */
31 static void
32 enlarge_buffer (register FILE *stream, int c)
34 struct memstream_info *info = (struct memstream_info *) stream->__cookie;
35 size_t need;
37 if (stream->__put_limit != stream->__buffer)
38 /* Record how much has actually been written into the buffer. */
39 *info->bufsize = stream->__bufp - stream->__buffer;
41 if (stream->__target != -1
42 && (size_t) stream->__target > *info->bufsize)
43 /* Our target (where the buffer maps to) is always zero except when
44 the user just did a SEEK_END fseek. If he sought within the
45 buffer, we need do nothing and will zero the target below. If he
46 sought past the end of the object, grow and zero-fill the buffer
47 up to the target address. */
48 need = stream->__target;
49 else
50 need = *info->bufsize;
52 /* We always need an extra character in the buffer. Either we are
53 writing C, or we are flushing and need to write a NUL terminator. */
54 ++need;
56 if (stream->__bufsize < need)
58 /* Enlarge the buffer. */
59 char *newbuf;
60 size_t newsize;
61 if (stream->__bufsize * 2 < need)
62 newsize = need;
63 else
64 newsize = stream->__bufsize * 2;
65 newbuf = (char *) realloc ((void *) stream->__buffer, newsize);
66 if (newbuf == NULL)
68 stream->__error = 1;
69 return;
71 *info->buffer = stream->__buffer = newbuf;
72 stream->__bufsize = newsize;
75 stream->__target = stream->__offset = 0;
76 stream->__get_limit = stream->__bufp = stream->__buffer + *info->bufsize;
77 stream->__put_limit = stream->__buffer + stream->__bufsize;
79 need -= stream->__bufp - stream->__buffer + 1;
80 if (need > 0)
82 /* We are extending the buffer after an fseek; zero-fill new space. */
83 memset (stream->__bufp, '\0', need);
84 stream->__bufp += need;
87 if (c != EOF)
88 *stream->__bufp++ = (unsigned char) c;
89 else
90 *stream->__bufp = '\0';
93 /* Seek function for memstreams.
94 There is no external state to munge. */
96 static int
97 seek (void *cookie, fpos_t *pos, int whence)
99 switch (whence)
101 case SEEK_SET:
102 case SEEK_CUR:
103 return 0;
105 case SEEK_END:
106 /* Return the position relative to the end of the object.
107 fseek has just flushed us, so the info is consistent. */
108 *pos += *((struct memstream_info *) cookie)->bufsize;
109 return 0;
111 default:
112 __libc_fatal ("memstream::seek called with bogus WHENCE\n");
113 return -1;
117 static int
118 free_info (void *cookie)
120 #if 0
121 struct memstream_info *info = (struct memstream_info *) cookie;
122 char *buf;
124 buf = (char *) realloc ((PTR) *info->buffer, *info->bufsize);
125 if (buf != NULL)
126 *info->buffer = buf;
127 #endif
129 free (cookie);
131 return 0;
134 /* Open a stream that writes into a malloc'd buffer that is expanded as
135 necessary. *BUFLOC and *SIZELOC are updated with the buffer's location
136 and the number of characters written on fflush or fclose. */
137 FILE *
138 open_memstream (bufloc, sizeloc)
139 char **bufloc;
140 size_t *sizeloc;
142 FILE *stream;
143 struct memstream_info *info;
145 if (bufloc == NULL || sizeloc == NULL)
147 __set_errno (EINVAL);
148 return NULL;
151 stream = fmemopen ((char *) NULL, BUFSIZ, "w+");
152 if (stream == NULL)
153 return NULL;
155 info = (struct memstream_info *) malloc (sizeof (struct memstream_info));
156 if (info == NULL)
158 int save = errno;
159 (void) fclose (stream);
160 __set_errno (save);
161 return NULL;
164 stream->__room_funcs.__output = enlarge_buffer;
165 stream->__io_funcs.__seek = seek;
166 stream->__io_funcs.__close = free_info;
167 stream->__cookie = (void *) info;
168 stream->__userbuf = 1;
170 info->buffer = bufloc;
171 info->bufsize = sizeloc;
173 *bufloc = stream->__buffer;
175 return stream;