00001 /*---------------------------------------------------------------------------*\ 00002 $Id: poll.c 182810 2009-03-18 02:09:13Z 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 /* 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 { 00124 /* Skip any bad FDs in the array. */ 00125 00126 if (pCur->fd < 0) 00127 continue; 00128 00129 if (pCur->events & POLLIN) 00130 { 00131 /* "Input Ready" notification desired. */ 00132 FD_SET (pCur->fd, pReadSet); 00133 } 00134 00135 if (pCur->events & POLLOUT) 00136 { 00137 /* "Output Possible" notification desired. */ 00138 FD_SET (pCur->fd, pWriteSet); 00139 } 00140 00141 if (pCur->events & POLLPRI) 00142 { 00143 /* 00144 "Exception Occurred" notification desired. (Exceptions 00145 include out of band data. 00146 */ 00147 FD_SET (pCur->fd, pExceptSet); 00148 } 00149 00150 max_fd = MAX (max_fd, pCur->fd); 00151 } 00152 00153 return max_fd; 00154 } 00155 00156 static struct timeval *map_timeout 00157 #if __STDC__ > 0 00158 (int poll_timeout, struct timeval *pSelTimeout) 00159 #else 00160 (poll_timeout, pSelTimeout) 00161 int poll_timeout; 00162 struct timeval *pSelTimeout; 00163 #endif 00164 { 00165 struct timeval *pResult; 00166 00167 /* 00168 Map the poll() timeout value into a select() timeout. The possible 00169 values of the poll() timeout value, and their meanings, are: 00170 00171 VALUE MEANING 00172 00173 -1 wait indefinitely (until signal occurs) 00174 0 return immediately, don't block 00175 >0 wait specified number of milliseconds 00176 00177 select() uses a "struct timeval", which specifies the timeout in 00178 seconds and microseconds, so the milliseconds value has to be mapped 00179 accordingly. 00180 */ 00181 00182 assert (pSelTimeout != (struct timeval *) NULL); 00183 00184 switch (poll_timeout) 00185 { 00186 case -1: 00187 /* 00188 A NULL timeout structure tells select() to wait indefinitely. 00189 */ 00190 pResult = (struct timeval *) NULL; 00191 break; 00192 00193 case 0: 00194 /* 00195 "Return immediately" (test) is specified by all zeros in 00196 a timeval structure. 00197 */ 00198 pSelTimeout->tv_sec = 0; 00199 pSelTimeout->tv_usec = 0; 00200 pResult = pSelTimeout; 00201 break; 00202 00203 default: 00204 /* Wait the specified number of milliseconds. */ 00205 pSelTimeout->tv_sec = poll_timeout / 1000; /* get seconds */ 00206 poll_timeout %= 1000; /* remove seconds */ 00207 pSelTimeout->tv_usec = poll_timeout * 1000; /* get microseconds */ 00208 pResult = pSelTimeout; 00209 break; 00210 } 00211 00212 00213 return pResult; 00214 } 00215 00216 static void map_select_results 00217 #if __STDC__ > 0 00218 (struct pollfd *pArray, 00219 unsigned long n_fds, 00220 fd_set *pReadSet, 00221 fd_set *pWriteSet, 00222 fd_set *pExceptSet) 00223 #else 00224 (pArray, n_fds, pReadSet, pWriteSet, pExceptSet) 00225 struct pollfd *pArray; 00226 unsigned long n_fds; 00227 fd_set *pReadSet; 00228 fd_set *pWriteSet; 00229 fd_set *pExceptSet; 00230 #endif 00231 { 00232 register unsigned long i; /* loop control */ 00233 register struct pollfd *pCur; /* current array element */ 00234 00235 for (i = 0, pCur = pArray; i < n_fds; i++, pCur++) 00236 { 00237 /* Skip any bad FDs in the array. */ 00238 00239 if (pCur->fd < 0) 00240 continue; 00241 00242 /* Exception events take priority over input events. */ 00243 00244 pCur->revents = 0; 00245 if (FD_ISSET (pCur->fd, pExceptSet)) 00246 pCur->revents |= POLLPRI; 00247 00248 else if (FD_ISSET (pCur->fd, pReadSet)) 00249 pCur->revents |= POLLIN; 00250 00251 if (FD_ISSET (pCur->fd, pWriteSet)) 00252 pCur->revents |= POLLOUT; 00253 } 00254 00255 return; 00256 } 00257 00258 /*---------------------------------------------------------------------------*\ 00259 Public Functions 00260 \*---------------------------------------------------------------------------*/ 00261 00262 int ast_internal_poll(struct pollfd *pArray, unsigned long n_fds, int timeout) 00263 { 00264 fd_set read_descs; /* input file descs */ 00265 fd_set write_descs; /* output file descs */ 00266 fd_set except_descs; /* exception descs */ 00267 struct timeval stime; /* select() timeout value */ 00268 int ready_descriptors; /* function result */ 00269 int max_fd = 0; /* maximum fd value */ 00270 struct timeval *pTimeout; /* actually passed */ 00271 00272 FD_ZERO (&read_descs); 00273 FD_ZERO (&write_descs); 00274 FD_ZERO (&except_descs); 00275 00276 /* Map the poll() file descriptor list in the select() data structures. */ 00277 00278 if (pArray) { 00279 max_fd = map_poll_spec (pArray, n_fds, 00280 &read_descs, &write_descs, &except_descs); 00281 } 00282 00283 /* Map the poll() timeout value in the select() timeout structure. */ 00284 00285 pTimeout = map_timeout (timeout, &stime); 00286 00287 /* Make the select() call. */ 00288 00289 ready_descriptors = select (max_fd + 1, &read_descs, &write_descs, 00290 &except_descs, pTimeout); 00291 00292 if (ready_descriptors >= 0) 00293 { 00294 map_select_results (pArray, n_fds, 00295 &read_descs, &write_descs, &except_descs); 00296 } 00297 00298 return ready_descriptors; 00299 } 00300 00301 #endif /* AST_POLL_COMPAT */