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[glibc.git] / stdio / fread.c
blobb0fe36bc28eac2da6fc0d78a98a2759770e50685
1 /* Copyright (C) 1991, 92, 95, 96, 97, 98 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 <errno.h>
20 #include <stdio.h>
21 #include <string.h>
24 #define default_func __default_room_functions.__input
26 /* Read NMEMB chunks of SIZE bytes each from STREAM into P. */
27 size_t
28 fread (p, size, nmemb, stream)
29 void *p;
30 size_t size;
31 size_t nmemb;
32 register FILE *stream;
34 register char *ptr = (char *) p;
35 register size_t to_read = size * nmemb;
36 size_t bytes = to_read;
38 if (!__validfp (stream) || !stream->__mode.__read)
40 __set_errno (EINVAL);
41 return 0;
43 if (feof (stream) || ferror (stream))
44 return 0;
45 if (p == NULL || to_read == 0)
46 return 0;
48 if (!stream->__seen || stream->__buffer == NULL || stream->__pushed_back)
50 /* This stream has never been seen before, or it has a character
51 pushed back. Call __fillbf to deal with those cases. Life will
52 be simpler after this call. */
53 int c = __fillbf (stream);
54 if (c == EOF)
55 return 0;
56 *ptr++ = c;
57 if (--to_read == 0)
58 return 1;
61 read_from_buffer:;
62 if (stream->__bufp < stream->__get_limit)
64 /* First off, empty out the buffer. */
65 register size_t copy = stream->__get_limit - stream->__bufp;
66 if (copy > to_read)
67 copy = to_read;
68 to_read -= copy;
69 if (copy > 20)
70 memcpy((void *) ptr, (void *) stream->__bufp, copy);
71 else
73 register size_t i;
74 for (i = 0; i < copy; ++i)
75 ptr[i] = stream->__bufp[i];
77 stream->__bufp += copy;
78 if (to_read == 0)
79 return nmemb;
80 ptr += copy;
83 /* Reading directly into the user's buffer doesn't help when
84 using a user-specified input buffer filling/expanding function,
85 so we don't do it in that case. */
86 if (to_read >= stream->__bufsize &&
87 stream->__room_funcs.__input == default_func &&
88 stream->__offset == stream->__target)
90 /* Read directly into the user's buffer. */
91 if (stream->__io_funcs.__read != NULL)
92 while (to_read > 0)
94 register int count;
95 count = (*stream->__io_funcs.__read) (stream->__cookie,
96 ptr, to_read);
97 if (count > 0)
99 to_read -= count;
100 if (stream->__offset != -1)
102 stream->__offset += count;
103 stream->__target += count;
105 ptr += count;
107 else if (count == 0)
109 stream->__eof = 1;
110 break;
112 else
114 stream->__error = 1;
115 break;
118 else
119 stream->__eof = 1;
121 else
123 int c = __fillbf (stream);
124 if (c == EOF)
125 return (bytes - to_read) / size;
126 *ptr++ = (char) c;
127 --to_read;
128 if (to_read > 0)
129 goto read_from_buffer;
132 return (bytes - to_read) / size;
135 weak_alias (fread, fread_unlocked)