00001 /*---------------------------------------------------------------------------*\ 00002 $Id: poll.c 239676 2010-01-13 11:19:17Z oej $ 00003 00004 NAME 00005 00006 poll - select(2)-based poll() emulation function for BSD systems. 00007 00008 SYNOPSIS 00009 #include "poll.h" 00010 00011 struct pollfd 00012 { 00013 int fd; 00014 short events; 00015 short revents; 00016 } 00017 00018 int poll (struct pollfd *pArray, unsigned long n_fds, int timeout) 00019 00020 DESCRIPTION 00021 00022 This file, and the accompanying "poll.h", implement the System V 00023 poll(2) system call for BSD systems (which typically do not provide 00024 poll()). Poll() provides a method for multiplexing input and output 00025 on multiple open file descriptors; in traditional BSD systems, that 00026 capability is provided by select(). While the semantics of select() 00027 differ from those of poll(), poll() can be readily emulated in terms 00028 of select() -- which is how this function is implemented. 00029 00030 REFERENCES 00031 Stevens, W. Richard. Unix Network Programming. Prentice-Hall, 1990. 00032 00033 NOTES 00034 1. This software requires an ANSI C compiler. 00035 00036 LICENSE 00037 00038 This software is released under the following license: 00039 00040 Copyright (c) 1995-2002 Brian M. Clapper 00041 All rights reserved. 00042 00043 Redistribution and use in source and binary forms are 00044 permitted provided that: (1) source distributions retain 00045 this entire copyright notice and comment; (2) modifications 00046 made to the software are prominently mentioned, and a copy 00047 of the original software (or a pointer to its location) are 00048 included; and (3) distributions including binaries display 00049 the following acknowledgement: "This product includes 00050 software developed by Brian M. Clapper <bmc@clapper.org>" 00051 in the documentation or other materials provided with the 00052 distribution. The name of the author may not be used to 00053 endorse or promote products derived from this software 00054 without specific prior written permission. 00055 00056 THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS 00057 OR IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE 00058 IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A 00059 PARTICULAR PURPOSE. 00060 00061 Effectively, this means you can do what you want with the software 00062 except remove this notice or take advantage of the author's name. 00063 If you modify the software and redistribute your modified version, 00064 you must indicate that your version is a modification of the 00065 original, and you must provide either a pointer to or a copy of the 00066 original. 00067 \*---------------------------------------------------------------------------*/ 00068 00069 00070 /*---------------------------------------------------------------------------*\ 00071 Includes 00072 \*---------------------------------------------------------------------------*/ 00073 00074 #include "asterisk.h" 00075 00076 #include <unistd.h> /* standard Unix definitions */ 00077 #include <sys/types.h> /* system types */ 00078 #include <sys/time.h> /* time definitions */ 00079 #include <assert.h> /* assertion macros */ 00080 #include <string.h> /* string functions */ 00081 00082 #include "asterisk/utils.h" /* this package */ 00083 #include "asterisk/poll-compat.h" /* this package */ 00084 00085 #ifdef AST_POLL_COMPAT 00086 00087 /*---------------------------------------------------------------------------*\ 00088 Private Functions 00089 \*---------------------------------------------------------------------------*/ 00090 00091 static int map_poll_spec 00092 #if __STDC__ > 0 00093 (struct pollfd *pArray, 00094 unsigned long n_fds, 00095 fd_set *pReadSet, 00096 fd_set *pWriteSet, 00097 fd_set *pExceptSet) 00098 #else 00099 (pArray, n_fds, pReadSet, pWriteSet, pExceptSet) 00100 struct pollfd *pArray; 00101 unsigned long n_fds; 00102 fd_set *pReadSet; 00103 fd_set *pWriteSet; 00104 fd_set *pExceptSet; 00105 #endif 00106 { 00107 register unsigned long i; /* loop control */ 00108 register struct pollfd *pCur; /* current array element */ 00109 register int max_fd = -1; /* return value */ 00110 00111 /*!\note 00112 * Map the poll() structures into the file descriptor sets required 00113 * by select(). 00114 */ 00115 for (i = 0, pCur = pArray; i < n_fds; i++, pCur++) { 00116 /* Skip any bad FDs in the array. */ 00117 00118 if (pCur->fd < 0) 00119 continue; 00120 00121 if (pCur->events & POLLIN) { 00122 /* "Input Ready" notification desired. */ 00123 FD_SET(pCur->fd, pReadSet); 00124 } 00125 00126 if (pCur->events & POLLOUT) { 00127 /* "Output Possible" notification desired. */ 00128 FD_SET(pCur->fd, pWriteSet); 00129 } 00130 00131 if (pCur->events & POLLPRI) { 00132 /*!\note 00133 * "Exception Occurred" notification desired. (Exceptions 00134 * include out of band data.) 00135 */ 00136 FD_SET(pCur->fd, pExceptSet); 00137 } 00138 00139 max_fd = MAX(max_fd, pCur->fd); 00140 } 00141 00142 return max_fd; 00143 } 00144 00145 static struct timeval *map_timeout 00146 #if __STDC__ > 0 00147 (int poll_timeout, struct timeval *pSelTimeout) 00148 #else 00149 (poll_timeout, pSelTimeout) 00150 int poll_timeout; 00151 struct timeval *pSelTimeout; 00152 #endif 00153 { 00154 struct timeval *pResult; 00155 00156 /*!\note 00157 * Map the poll() timeout value into a select() timeout. The possible 00158 * values of the poll() timeout value, and their meanings, are: 00159 * 00160 * VALUE MEANING 00161 * 00162 * -1 wait indefinitely (until signal occurs) 00163 * 0 return immediately, don't block 00164 * >0 wait specified number of milliseconds 00165 * 00166 * select() uses a "struct timeval", which specifies the timeout in 00167 * seconds and microseconds, so the milliseconds value has to be mapped 00168 * accordingly. 00169 */ 00170 00171 assert(pSelTimeout != (struct timeval *) NULL); 00172 00173 switch (poll_timeout) { 00174 case -1: 00175 /* 00176 * A NULL timeout structure tells select() to wait indefinitely. 00177 */ 00178 pResult = (struct timeval *) NULL; 00179 break; 00180 00181 case 0: 00182 /* 00183 * "Return immediately" (test) is specified by all zeros in 00184 * a timeval structure. 00185 */ 00186 pSelTimeout->tv_sec = 0; 00187 pSelTimeout->tv_usec = 0; 00188 pResult = pSelTimeout; 00189 break; 00190 00191 default: 00192 /* Wait the specified number of milliseconds. */ 00193 pSelTimeout->tv_sec = poll_timeout / 1000; /* get seconds */ 00194 poll_timeout %= 1000; /* remove seconds */ 00195 pSelTimeout->tv_usec = poll_timeout * 1000; /* get microseconds */ 00196 pResult = pSelTimeout; 00197 break; 00198 } 00199 00200 return pResult; 00201 } 00202 00203 static void map_select_results 00204 #if __STDC__ > 0 00205 (struct pollfd *pArray, 00206 unsigned long n_fds, 00207 fd_set *pReadSet, 00208 fd_set *pWriteSet, 00209 fd_set *pExceptSet) 00210 #else 00211 (pArray, n_fds, pReadSet, pWriteSet, pExceptSet) 00212 struct pollfd *pArray; 00213 unsigned long n_fds; 00214 fd_set *pReadSet; 00215 fd_set *pWriteSet; 00216 fd_set *pExceptSet; 00217 #endif 00218 { 00219 register unsigned long i; /* loop control */ 00220 register struct pollfd *pCur; /* current array element */ 00221 00222 for (i = 0, pCur = pArray; i < n_fds; i++, pCur++) { 00223 /* Skip any bad FDs in the array. */ 00224 00225 if (pCur->fd < 0) { 00226 continue; 00227 } 00228 00229 /* Exception events take priority over input events. */ 00230 00231 pCur->revents = 0; 00232 if (FD_ISSET (pCur->fd, pExceptSet)) { 00233 pCur->revents |= POLLPRI; 00234 } else if (FD_ISSET (pCur->fd, pReadSet)) { 00235 pCur->revents |= POLLIN; 00236 } 00237 00238 if (FD_ISSET (pCur->fd, pWriteSet)) { 00239 pCur->revents |= POLLOUT; 00240 } 00241 } 00242 00243 return; 00244 } 00245 00246 /*---------------------------------------------------------------------------*\ 00247 Public Functions 00248 \*---------------------------------------------------------------------------*/ 00249 00250 int ast_internal_poll(struct pollfd *pArray, unsigned long n_fds, int timeout) 00251 { 00252 fd_set read_descs; /* input file descs */ 00253 fd_set write_descs; /* output file descs */ 00254 fd_set except_descs; /* exception descs */ 00255 struct timeval stime; /* select() timeout value */ 00256 int ready_descriptors; /* function result */ 00257 int max_fd = 0; /* maximum fd value */ 00258 struct timeval *pTimeout; /* actually passed */ 00259 00260 FD_ZERO (&read_descs); 00261 FD_ZERO (&write_descs); 00262 FD_ZERO (&except_descs); 00263 00264 /* Map the poll() file descriptor list in the select() data structures. */ 00265 00266 if (pArray) { 00267 max_fd = map_poll_spec (pArray, n_fds, 00268 &read_descs, &write_descs, &except_descs); 00269 } 00270 00271 /* Map the poll() timeout value in the select() timeout structure. */ 00272 pTimeout = map_timeout(timeout, &stime); 00273 00274 /* Make the select() call. */ 00275 ready_descriptors = select(max_fd + 1, &read_descs, &write_descs, 00276 &except_descs, pTimeout); 00277 00278 if (ready_descriptors >= 0) { 00279 map_select_results(pArray, n_fds, &read_descs, &write_descs, &except_descs); 00280 } 00281 00282 return ready_descriptors; 00283 } 00284 00285 #endif /* AST_POLL_COMPAT */