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
34static 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
48ssize_t					/* O - Bytes read or -1 on error */
49cupsBackChannelRead(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
99ssize_t					/* O - Bytes written or -1 on error */
100cupsBackChannelWrite(
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
176static void
177cups_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