1 /*
2 * Backchannel functions for CUPS.
3 *
4 * Copyright 2007-2014 by Apple Inc.
5 * Copyright 1997-2007 by Easy Software Products.
6 *
7 * These coded instructions, statements, and computer programs are the
8 * property of Apple Inc. and are protected by Federal copyright
9 * law. Distribution and use rights are outlined in the file "LICENSE.txt"
10 * which should have been included with this file. If this file is
11 * missing or damaged, see the license at "http://www.cups.org/".
12 *
13 * This file is subject to the Apple OS-Developed Software exception.
14 */
15
16 /*
17 * Include necessary headers...
18 */
19
20 #include "cups.h"
21 #include <errno.h>
22 #ifdef _WIN32
23 # include <io.h>
24 # include <fcntl.h>
25 #else
26 # include <sys/time.h>
27 #endif /* _WIN32 */
28
29
30 /*
31 * Local functions...
32 */
33
34 static void cups_setup(fd_set *set, struct timeval *tval,
35 double timeout);
36
37
38 /*
39 * 'cupsBackChannelRead()' - Read data from the backchannel.
40 *
41 * Reads up to "bytes" bytes from the backchannel/backend. The "timeout"
42 * parameter controls how many seconds to wait for the data - use 0.0 to
43 * return immediately if there is no data, -1.0 to wait for data indefinitely.
44 *
45 * @since CUPS 1.2/macOS 10.5@
46 */
47
48 ssize_t /* O - Bytes read or -1 on error */
cupsBackChannelRead(char * buffer,size_t bytes,double timeout)49 cupsBackChannelRead(char *buffer, /* I - Buffer to read into */
50 size_t bytes, /* I - Bytes to read */
51 double timeout) /* I - Timeout in seconds, typically 0.0 to poll */
52 {
53 fd_set input; /* Input set */
54 struct timeval tval; /* Timeout value */
55 int status; /* Select status */
56
57
58 /*
59 * Wait for input ready.
60 */
61
62 do
63 {
64 cups_setup(&input, &tval, timeout);
65
66 if (timeout < 0.0)
67 status = select(4, &input, NULL, NULL, NULL);
68 else
69 status = select(4, &input, NULL, NULL, &tval);
70 }
71 while (status < 0 && errno != EINTR && errno != EAGAIN);
72
73 if (status < 0)
74 return (-1); /* Timeout! */
75
76 /*
77 * Read bytes from the pipe...
78 */
79
80 #ifdef _WIN32
81 return ((ssize_t)_read(3, buffer, (unsigned)bytes));
82 #else
83 return (read(3, buffer, bytes));
84 #endif /* _WIN32 */
85 }
86
87
88 /*
89 * 'cupsBackChannelWrite()' - Write data to the backchannel.
90 *
91 * Writes "bytes" bytes to the backchannel/filter. The "timeout" parameter
92 * controls how many seconds to wait for the data to be written - use
93 * 0.0 to return immediately if the data cannot be written, -1.0 to wait
94 * indefinitely.
95 *
96 * @since CUPS 1.2/macOS 10.5@
97 */
98
99 ssize_t /* O - Bytes written or -1 on error */
cupsBackChannelWrite(const char * buffer,size_t bytes,double timeout)100 cupsBackChannelWrite(
101 const char *buffer, /* I - Buffer to write */
102 size_t bytes, /* I - Bytes to write */
103 double timeout) /* I - Timeout in seconds, typically 1.0 */
104 {
105 fd_set output; /* Output set */
106 struct timeval tval; /* Timeout value */
107 int status; /* Select status */
108 ssize_t count; /* Current bytes */
109 size_t total; /* Total bytes */
110
111
112 /*
113 * Write all bytes...
114 */
115
116 total = 0;
117
118 while (total < bytes)
119 {
120 /*
121 * Wait for write-ready...
122 */
123
124 do
125 {
126 cups_setup(&output, &tval, timeout);
127
128 if (timeout < 0.0)
129 status = select(4, NULL, &output, NULL, NULL);
130 else
131 status = select(4, NULL, &output, NULL, &tval);
132 }
133 while (status < 0 && errno != EINTR && errno != EAGAIN);
134
135 if (status <= 0)
136 return (-1); /* Timeout! */
137
138 /*
139 * Write bytes to the pipe...
140 */
141
142 #ifdef _WIN32
143 count = (ssize_t)_write(3, buffer, (unsigned)(bytes - total));
144 #else
145 count = write(3, buffer, bytes - total);
146 #endif /* _WIN32 */
147
148 if (count < 0)
149 {
150 /*
151 * Write error - abort on fatal errors...
152 */
153
154 if (errno != EINTR && errno != EAGAIN)
155 return (-1);
156 }
157 else
158 {
159 /*
160 * Write succeeded, update buffer pointer and total count...
161 */
162
163 buffer += count;
164 total += (size_t)count;
165 }
166 }
167
168 return ((ssize_t)bytes);
169 }
170
171
172 /*
173 * 'cups_setup()' - Setup select()
174 */
175
176 static void
cups_setup(fd_set * set,struct timeval * tval,double timeout)177 cups_setup(fd_set *set, /* I - Set for select() */
178 struct timeval *tval, /* I - Timer value */
179 double timeout) /* I - Timeout in seconds */
180 {
181 tval->tv_sec = (int)timeout;
182 tval->tv_usec = (int)(1000000.0 * (timeout - tval->tv_sec));
183
184 FD_ZERO(set);
185 FD_SET(3, set);
186 }
187