/* * "$Id: backchannel.c 7616 2008-05-28 00:34:13Z mike $" * * Backchannel functions for CUPS. * * Copyright 2007-2012 by Apple Inc. * Copyright 1997-2007 by Easy Software Products. * * These coded instructions, statements, and computer programs are the * property of Apple Inc. and are protected by Federal copyright * law. Distribution and use rights are outlined in the file "LICENSE.txt" * which should have been included with this file. If this file is * file is missing or damaged, see the license at "http://www.cups.org/". * * This file is subject to the Apple OS-Developed Software exception. * * Contents: * * cupsBackChannelRead() - Read data from the backchannel. * cupsBackChannelWrite() - Write data to the backchannel. * cups_setup() - Setup select() */ /* * Include necessary headers... */ #include "cups.h" #include <errno.h> #ifdef WIN32 # include <io.h> # include <fcntl.h> #else # include <sys/time.h> #endif /* WIN32 */ /* * Local functions... */ static void cups_setup(fd_set *set, struct timeval *tval, double timeout); /* * 'cupsBackChannelRead()' - Read data from the backchannel. * * Reads up to "bytes" bytes from the backchannel/backend. The "timeout" * parameter controls how many seconds to wait for the data - use 0.0 to * return immediately if there is no data, -1.0 to wait for data indefinitely. * * @since CUPS 1.2/OS X 10.5@ */ ssize_t /* O - Bytes read or -1 on error */ cupsBackChannelRead(char *buffer, /* I - Buffer to read into */ size_t bytes, /* I - Bytes to read */ double timeout) /* I - Timeout in seconds, typically 0.0 to poll */ { fd_set input; /* Input set */ struct timeval tval; /* Timeout value */ int status; /* Select status */ /* * Wait for input ready. */ do { cups_setup(&input, &tval, timeout); if (timeout < 0.0) status = select(4, &input, NULL, NULL, NULL); else status = select(4, &input, NULL, NULL, &tval); } while (status < 0 && errno != EINTR && errno != EAGAIN); if (status < 0) return (-1); /* Timeout! */ /* * Read bytes from the pipe... */ #ifdef WIN32 return ((ssize_t)_read(3, buffer, (unsigned)bytes)); #else return (read(3, buffer, bytes)); #endif /* WIN32 */ } /* * 'cupsBackChannelWrite()' - Write data to the backchannel. * * Writes "bytes" bytes to the backchannel/filter. The "timeout" parameter * controls how many seconds to wait for the data to be written - use * 0.0 to return immediately if the data cannot be written, -1.0 to wait * indefinitely. * * @since CUPS 1.2/OS X 10.5@ */ ssize_t /* O - Bytes written or -1 on error */ cupsBackChannelWrite( const char *buffer, /* I - Buffer to write */ size_t bytes, /* I - Bytes to write */ double timeout) /* I - Timeout in seconds, typically 1.0 */ { fd_set output; /* Output set */ struct timeval tval; /* Timeout value */ int status; /* Select status */ ssize_t count; /* Current bytes */ size_t total; /* Total bytes */ /* * Write all bytes... */ total = 0; while (total < bytes) { /* * Wait for write-ready... */ do { cups_setup(&output, &tval, timeout); if (timeout < 0.0) status = select(4, NULL, &output, NULL, NULL); else status = select(4, NULL, &output, NULL, &tval); } while (status < 0 && errno != EINTR && errno != EAGAIN); if (status <= 0) return (-1); /* Timeout! */ /* * Write bytes to the pipe... */ #ifdef WIN32 count = (ssize_t)_write(3, buffer, (unsigned)(bytes - total)); #else count = write(3, buffer, bytes - total); #endif /* WIN32 */ if (count < 0) { /* * Write error - abort on fatal errors... */ if (errno != EINTR && errno != EAGAIN) return (-1); } else { /* * Write succeeded, update buffer pointer and total count... */ buffer += count; total += count; } } return ((ssize_t)bytes); } /* * 'cups_setup()' - Setup select() */ static void cups_setup(fd_set *set, /* I - Set for select() */ struct timeval *tval, /* I - Timer value */ double timeout) /* I - Timeout in seconds */ { tval->tv_sec = (int)timeout; tval->tv_usec = (int)(1000000.0 * (timeout - tval->tv_sec)); FD_ZERO(set); FD_SET(3, set); } /* * End of "$Id: backchannel.c 7616 2008-05-28 00:34:13Z mike $". */