1 /*
2 * Backchannel functions for CUPS.
3 *
4 * Copyright 2007-2014 by Apple Inc.
5 * Copyright 1997-2007 by Easy Software Products.
6 *
7 * Licensed under Apache License v2.0. See the file "LICENSE" for more information.
8 */
9
10 /*
11 * Include necessary headers...
12 */
13
14 #include "cups.h"
15 #include "sidechannel.h"
16 #include <errno.h>
17 #ifdef _WIN32
18 # include <io.h>
19 # include <fcntl.h>
20 #else
21 # include <sys/time.h>
22 #endif /* _WIN32 */
23
24
25 /*
26 * Local functions...
27 */
28
29 static void cups_setup(fd_set *set, struct timeval *tval,
30 double timeout);
31
32
33 /*
34 * 'cupsBackChannelRead()' - Read data from the backchannel.
35 *
36 * Reads up to "bytes" bytes from the backchannel/backend. The "timeout"
37 * parameter controls how many seconds to wait for the data - use 0.0 to
38 * return immediately if there is no data, -1.0 to wait for data indefinitely.
39 *
40 * @since CUPS 1.2/macOS 10.5@
41 */
42
43 ssize_t /* O - Bytes read or -1 on error */
cupsBackChannelRead(char * buffer,size_t bytes,double timeout)44 cupsBackChannelRead(char *buffer, /* I - Buffer to read into */
45 size_t bytes, /* I - Bytes to read */
46 double timeout) /* I - Timeout in seconds, typically 0.0 to poll */
47 {
48 fd_set input; /* Input set */
49 struct timeval tval; /* Timeout value */
50 int status; /* Select status */
51
52
53 /*
54 * Wait for input ready.
55 */
56
57 do
58 {
59 cups_setup(&input, &tval, timeout);
60
61 if (timeout < 0.0)
62 status = select(4, &input, NULL, NULL, NULL);
63 else
64 status = select(4, &input, NULL, NULL, &tval);
65 }
66 while (status < 0 && errno != EINTR && errno != EAGAIN);
67
68 if (status < 0)
69 return (-1); /* Timeout! */
70
71 /*
72 * Read bytes from the pipe...
73 */
74
75 #ifdef _WIN32
76 return ((ssize_t)_read(3, buffer, (unsigned)bytes));
77 #else
78 return (read(3, buffer, bytes));
79 #endif /* _WIN32 */
80 }
81
82
83 /*
84 * 'cupsBackChannelWrite()' - Write data to the backchannel.
85 *
86 * Writes "bytes" bytes to the backchannel/filter. The "timeout" parameter
87 * controls how many seconds to wait for the data to be written - use
88 * 0.0 to return immediately if the data cannot be written, -1.0 to wait
89 * indefinitely.
90 *
91 * @since CUPS 1.2/macOS 10.5@
92 */
93
94 ssize_t /* O - Bytes written or -1 on error */
cupsBackChannelWrite(const char * buffer,size_t bytes,double timeout)95 cupsBackChannelWrite(
96 const char *buffer, /* I - Buffer to write */
97 size_t bytes, /* I - Bytes to write */
98 double timeout) /* I - Timeout in seconds, typically 1.0 */
99 {
100 fd_set output; /* Output set */
101 struct timeval tval; /* Timeout value */
102 int status; /* Select status */
103 ssize_t count; /* Current bytes */
104 size_t total; /* Total bytes */
105
106
107 /*
108 * Write all bytes...
109 */
110
111 total = 0;
112
113 while (total < bytes)
114 {
115 /*
116 * Wait for write-ready...
117 */
118
119 do
120 {
121 cups_setup(&output, &tval, timeout);
122
123 if (timeout < 0.0)
124 status = select(4, NULL, &output, NULL, NULL);
125 else
126 status = select(4, NULL, &output, NULL, &tval);
127 }
128 while (status < 0 && errno != EINTR && errno != EAGAIN);
129
130 if (status <= 0)
131 return (-1); /* Timeout! */
132
133 /*
134 * Write bytes to the pipe...
135 */
136
137 #ifdef _WIN32
138 count = (ssize_t)_write(3, buffer, (unsigned)(bytes - total));
139 #else
140 count = write(3, buffer, bytes - total);
141 #endif /* _WIN32 */
142
143 if (count < 0)
144 {
145 /*
146 * Write error - abort on fatal errors...
147 */
148
149 if (errno != EINTR && errno != EAGAIN)
150 return (-1);
151 }
152 else
153 {
154 /*
155 * Write succeeded, update buffer pointer and total count...
156 */
157
158 buffer += count;
159 total += (size_t)count;
160 }
161 }
162
163 return ((ssize_t)bytes);
164 }
165
166
167 /*
168 * 'cups_setup()' - Setup select()
169 */
170
171 static void
cups_setup(fd_set * set,struct timeval * tval,double timeout)172 cups_setup(fd_set *set, /* I - Set for select() */
173 struct timeval *tval, /* I - Timer value */
174 double timeout) /* I - Timeout in seconds */
175 {
176 tval->tv_sec = (int)timeout;
177 tval->tv_usec = (int)(1000000.0 * (timeout - tval->tv_sec));
178
179 FD_ZERO(set);
180 FD_SET(3, set);
181 }
182