summaryrefslogtreecommitdiff
path: root/ext/io/nonblock/nonblock.c
blob: b54feba4ae28aed71c36db716feb8c00885814f9 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
/**********************************************************************

  io/nonblock.c -

  $Author$
  created at: Tue Jul 14 21:53:18 2009

  All the files in this distribution are covered under the Ruby's
  license (see the file COPYING).

**********************************************************************/

#include "ruby.h"
#include "ruby/io.h"
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#include <fcntl.h>

#ifdef F_GETFL
static int
io_nonblock_mode(int fd)
{
    int f = fcntl(fd, F_GETFL);
    if (f == -1) rb_sys_fail(0);
    return f;
}
#else
#define io_nonblock_mode(fd) ((void)(fd), 0)
#endif

#ifdef F_GETFL
/*
 * call-seq:
 *   io.nonblock? -> boolean
 *
 * Returns +true+ if an IO object is in non-blocking mode.
 */
static VALUE
rb_io_nonblock_p(VALUE io)
{
    rb_io_t *fptr;
    GetOpenFile(io, fptr);
    if (io_nonblock_mode(fptr->fd) & O_NONBLOCK)
	return Qtrue;
    return Qfalse;
}
#else
#define rb_io_nonblock_p rb_f_notimplement
#endif

#ifdef F_SETFL
static int
io_nonblock_set(int fd, int f, int nb)
{
    if (nb) {
	if ((f & O_NONBLOCK) != 0)
	    return 0;
	f |= O_NONBLOCK;
    }
    else {
	if ((f & O_NONBLOCK) == 0)
	    return 0;
	f &= ~O_NONBLOCK;
    }
    if (fcntl(fd, F_SETFL, f) == -1)
	rb_sys_fail(0);
    return 1;
}

/*
 * call-seq:
 *   io.nonblock = boolean -> boolean
 *
 * Enables non-blocking mode on a stream when set to
 * +true+, and blocking mode when set to +false+.
 *
 * This method set or clear O_NONBLOCK flag for the file descriptor
 * in <em>ios</em>.
 *
 * The behavior of most IO methods is not affected by this flag
 * because they retry system calls to complete their task
 * after EAGAIN and partial read/write.
 * (An exception is IO#syswrite which doesn't retry.)
 *
 * This method can be used to clear non-blocking mode of standard I/O.
 * Since nonblocking methods (read_nonblock, etc.) set non-blocking mode but
 * they doesn't clear it, this method is usable as follows.
 *
 *   END { STDOUT.nonblock = false }
 *   STDOUT.write_nonblock("foo")
 *
 * Since the flag is shared across processes and
 * many non-Ruby commands doesn't expect standard I/O with non-blocking mode,
 * it would be safe to clear the flag before Ruby program exits.
 *
 * For example following Ruby program leaves STDIN/STDOUT/STDER non-blocking mode.
 * (STDIN, STDOUT and STDERR are connected to a terminal.
 * So making one of them nonblocking-mode effects other two.)
 * Thus cat command try to read from standard input and
 * it causes "Resource temporarily unavailable" error (EAGAIN).
 *
 *   % ruby -e '
 *   STDOUT.write_nonblock("foo\n")'; cat
 *   foo
 *   cat: -: Resource temporarily unavailable
 *
 * Clearing the flag makes the behavior of cat command normal.
 * (cat command waits input from standard input.)
 *
 *   % ruby -rio/nonblock -e '
 *   END { STDOUT.nonblock = false }
 *   STDOUT.write_nonblock("foo")
 *   '; cat
 *   foo
 *
 */
static VALUE
rb_io_nonblock_set(VALUE io, VALUE nb)
{
    rb_io_t *fptr;
    GetOpenFile(io, fptr);
    if (RTEST(nb))
	rb_io_set_nonblock(fptr);
    else
	io_nonblock_set(fptr->fd, io_nonblock_mode(fptr->fd), RTEST(nb));
    return io;
}

static VALUE
io_nonblock_restore(VALUE arg)
{
    int *restore = (int *)arg;
    if (fcntl(restore[0], F_SETFL, restore[1]) == -1)
	rb_sys_fail(0);
    return Qnil;
}

/*
 * call-seq:
 *   io.nonblock {|io| } -> io
 *   io.nonblock(boolean) {|io| } -> io
 *
 * Yields +self+ in non-blocking mode.
 *
 * When +false+ is given as an argument, +self+ is yielded in blocking mode.
 * The original mode is restored after the block is executed.
 */
static VALUE
rb_io_nonblock_block(int argc, VALUE *argv, VALUE io)
{
    int nb = 1;
    rb_io_t *fptr;
    int f, restore[2];

    GetOpenFile(io, fptr);
    if (argc > 0) {
	VALUE v;
	rb_scan_args(argc, argv, "01", &v);
	nb = RTEST(v);
    }
    f = io_nonblock_mode(fptr->fd);
    restore[0] = fptr->fd;
    restore[1] = f;
    if (!io_nonblock_set(fptr->fd, f, nb))
	return rb_yield(io);
    return rb_ensure(rb_yield, io, io_nonblock_restore, (VALUE)restore);
}
#else
#define rb_io_nonblock_set rb_f_notimplement
#define rb_io_nonblock_block rb_f_notimplement
#endif

void
Init_nonblock(void)
{
    rb_define_method(rb_cIO, "nonblock?", rb_io_nonblock_p, 0);
    rb_define_method(rb_cIO, "nonblock=", rb_io_nonblock_set, 1);
    rb_define_method(rb_cIO, "nonblock", rb_io_nonblock_block, -1);
}