00001 /*---------------------------------------------------------------------------*\ 00002 $Id: poll.c 182946 2009-03-18 14:32:47Z russell $ 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/poll-compat.h" /* this package */ 00083 00084 #ifdef AST_POLL_COMPAT 00085 00086 /*---------------------------------------------------------------------------*\ 00087 Macros 00088 \*---------------------------------------------------------------------------*/ 00089 00090 #ifndef MAX 00091 #define MAX(a,b) ((a) > (b) ? (a) : (b)) 00092 #endif 00093 00094 /*---------------------------------------------------------------------------*\ 00095 Private Functions 00096 \*---------------------------------------------------------------------------*/ 00097 00098 static int map_poll_spec 00099 #if __STDC__ > 0 00100 (struct pollfd *pArray, 00101 unsigned long n_fds, 00102 fd_set *pReadSet, 00103 fd_set *pWriteSet, 00104 fd_set *pExceptSet) 00105 #else 00106 (pArray, n_fds, pReadSet, pWriteSet, pExceptSet) 00107 struct pollfd *pArray; 00108 unsigned long n_fds; 00109 fd_set *pReadSet; 00110 fd_set *pWriteSet; 00111 fd_set *pExceptSet; 00112 #endif 00113 { 00114 register unsigned long i; /* loop control */ 00115 register struct pollfd *pCur; /* current array element */ 00116 register int max_fd = -1; /* return value */ 00117 00118 /*!\note 00119 * Map the poll() structures into the file descriptor sets required 00120 * by select(). 00121 */ 00122 for (i = 0, pCur = pArray; i < n_fds; i++, pCur++) { 00123 /* Skip any bad FDs in the array. */ 00124 00125 if (pCur->fd < 0) 00126 continue; 00127 00128 if (pCur->events & POLLIN) { 00129 /* "Input Ready" notification desired. */ 00130 FD_SET(pCur->fd, pReadSet); 00131 } 00132 00133 if (pCur->events & POLLOUT) { 00134 /* "Output Possible" notification desired. */ 00135 FD_SET(pCur->fd, pWriteSet); 00136 } 00137 00138 if (pCur->events & POLLPRI) { 00139 /*!\note 00140 * "Exception Occurred" notification desired. (Exceptions 00141 * include out of band data.) 00142 */ 00143 FD_SET(pCur->fd, pExceptSet); 00144 } 00145 00146 max_fd = MAX(max_fd, pCur->fd); 00147 } 00148 00149 return max_fd; 00150 } 00151 00152 static struct timeval *map_timeout 00153 #if __STDC__ > 0 00154 (int poll_timeout, struct timeval *pSelTimeout) 00155 #else 00156 (poll_timeout, pSelTimeout) 00157 int poll_timeout; 00158 struct timeval *pSelTimeout; 00159 #endif 00160 { 00161 struct timeval *pResult; 00162 00163 /*!\note 00164 * Map the poll() timeout value into a select() timeout. The possible 00165 * values of the poll() timeout value, and their meanings, are: 00166 * 00167 * VALUE MEANING 00168 * 00169 * -1 wait indefinitely (until signal occurs) 00170 * 0 return immediately, don't block 00171 * >0 wait specified number of milliseconds 00172 * 00173 * select() uses a "struct timeval", which specifies the timeout in 00174 * seconds and microseconds, so the milliseconds value has to be mapped 00175 * accordingly. 00176 */ 00177 00178 assert(pSelTimeout != (struct timeval *) NULL); 00179 00180 switch (poll_timeout) { 00181 case -1: 00182 /* 00183 * A NULL timeout structure tells select() to wait indefinitely. 00184 */ 00185 pResult = (struct timeval *) NULL; 00186 break; 00187 00188 case 0: 00189 /* 00190 * "Return immediately" (test) is specified by all zeros in 00191 * a timeval structure. 00192 */ 00193 pSelTimeout->tv_sec = 0; 00194 pSelTimeout->tv_usec = 0; 00195 pResult = pSelTimeout; 00196 break; 00197 00198 default: 00199 /* Wait the specified number of milliseconds. */ 00200 pSelTimeout->tv_sec = poll_timeout / 1000; /* get seconds */ 00201 poll_timeout %= 1000; /* remove seconds */ 00202 pSelTimeout->tv_usec = poll_timeout * 1000; /* get microseconds */ 00203 pResult = pSelTimeout; 00204 break; 00205 } 00206 00207 return pResult; 00208 } 00209 00210 static void map_select_results 00211 #if __STDC__ > 0 00212 (struct pollfd *pArray, 00213 unsigned long n_fds, 00214 fd_set *pReadSet, 00215 fd_set *pWriteSet, 00216 fd_set *pExceptSet) 00217 #else 00218 (pArray, n_fds, pReadSet, pWriteSet, pExceptSet) 00219 struct pollfd *pArray; 00220 unsigned long n_fds; 00221 fd_set *pReadSet; 00222 fd_set *pWriteSet; 00223 fd_set *pExceptSet; 00224 #endif 00225 { 00226 register unsigned long i; /* loop control */ 00227 register struct pollfd *pCur; /* current array element */ 00228 00229 for (i = 0, pCur = pArray; i < n_fds; i++, pCur++) { 00230 /* Skip any bad FDs in the array. */ 00231 00232 if (pCur->fd < 0) { 00233 continue; 00234 } 00235 00236 /* Exception events take priority over input events. */ 00237 00238 pCur->revents = 0; 00239 if (FD_ISSET (pCur->fd, pExceptSet)) { 00240 pCur->revents |= POLLPRI; 00241 } else if (FD_ISSET (pCur->fd, pReadSet)) { 00242 pCur->revents |= POLLIN; 00243 } 00244 00245 if (FD_ISSET (pCur->fd, pWriteSet)) { 00246 pCur->revents |= POLLOUT; 00247 } 00248 } 00249 00250 return; 00251 } 00252 00253 /*---------------------------------------------------------------------------*\ 00254 Public Functions 00255 \*---------------------------------------------------------------------------*/ 00256 00257 int ast_internal_poll(struct pollfd *pArray, unsigned long n_fds, int timeout) 00258 { 00259 fd_set read_descs; /* input file descs */ 00260 fd_set write_descs; /* output file descs */ 00261 fd_set except_descs; /* exception descs */ 00262 struct timeval stime; /* select() timeout value */ 00263 int ready_descriptors; /* function result */ 00264 int max_fd = 0; /* maximum fd value */ 00265 struct timeval *pTimeout; /* actually passed */ 00266 00267 FD_ZERO (&read_descs); 00268 FD_ZERO (&write_descs); 00269 FD_ZERO (&except_descs); 00270 00271 /* Map the poll() file descriptor list in the select() data structures. */ 00272 00273 if (pArray) { 00274 max_fd = map_poll_spec (pArray, n_fds, 00275 &read_descs, &write_descs, &except_descs); 00276 } 00277 00278 /* Map the poll() timeout value in the select() timeout structure. */ 00279 pTimeout = map_timeout(timeout, &stime); 00280 00281 /* Make the select() call. */ 00282 ready_descriptors = select(max_fd + 1, &read_descs, &write_descs, 00283 &except_descs, pTimeout); 00284 00285 if (ready_descriptors >= 0) { 00286 map_select_results(pArray, n_fds, &read_descs, &write_descs, &except_descs); 00287 } 00288 00289 return ready_descriptors; 00290 } 00291 00292 #endif /* AST_POLL_COMPAT */