cdsa/cdsa_utilities/selector.cpp

   1 /*
   2  * Copyright (c) 2000-2001 Apple Computer, Inc. All Rights Reserved.
   3  *
   4  * The contents of this file constitute Original Code as defined in and are
   5  * subject to the Apple Public Source License Version 1.2 (the 'License').
   6  * You may not use this file except in compliance with the License. Please obtain
   7  * a copy of the License at http://www.apple.com/publicsource and read it before
   8  * using this file.
   9  *
  10  * This Original Code and all software distributed under the License are
  11  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESS
  12  * OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, INCLUDING WITHOUT
  13  * LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
  14  * PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. Please see the License for the
  15  * specific language governing rights and limitations under the License.
  16  */
  17
  18
  19 //
  20 // selector - I/O stream multiplexing
  21 //
  22 #include "selector.h"
  23 #include <Security/debugging.h>
  24 #include <algorithm>    // min/max
  25
  26
  27 namespace Security {
  28 namespace UnixPlusPlus {
  29
  30
  31 //
  32 // construct a Selector object.
  33 //
  34 Selector::Selector() : fdMin(INT_MAX), fdMax(-1)
  35 {
  36     // initially allocate room for FD_SETSIZE file descriptors (usually good enough)
  37     fdSetSize = FD_SETSIZE / NFDBITS;
  38     inSet.grow(0, fdSetSize);
  39     outSet.grow(0, fdSetSize);
  40     errSet.grow(0, fdSetSize);
  41 }
  42
  43 Selector::~Selector()
  44 { }
  45
  46
  47 //
  48 // Add a Client to a Selector
  49 //
  50 void Selector::add(int fd, Client &client, Type type)
  51 {
  52     // plausibility checks
  53     assert(!client.isActive());         // one Selector per client, and no re-adding
  54     assert(fd >= 0);
  55
  56     secdebug("selector", "add client %p fd %d type=%d", &client, fd, type);
  57
  58     // grow FDSets if needed
  59     unsigned int pos = fd / NFDBITS;
  60     if (pos >= fdSetSize) {
  61         int newSize = (fd - 1) / NFDBITS + 2;   // as much as needed + 1 spare word
  62         inSet.grow(fdSetSize, newSize);
  63         outSet.grow(fdSetSize, newSize);
  64         errSet.grow(fdSetSize, newSize);
  65     }
  66
  67     // adjust boundaries
  68     if (fd < fdMin)
  69         fdMin = fd;
  70     if (fd > fdMax)
  71         fdMax = fd;
  72
  73     // add client
  74     Client * &slot = clientMap[fd];
  75     assert(!slot);
  76     slot = &client;
  77     client.mFd = fd;
  78     client.mSelector = this;
  79     client.mEvents = type;
  80     set(fd, type);
  81 }
  82
  83
  84 //
  85 // Remove a Client from a Selector
  86 //
  87 void Selector::remove(int fd)
  88 {
  89     // sanity checks
  90     assert(fd >= 0);
  91     ClientMap::iterator it = clientMap.find(fd);
  92     assert(it != clientMap.end());
  93     assert(it->second->mSelector == this);
  94
  95     secdebug("selector", "remove client %p fd %d", it->second, fd);
  96
  97     // remove from FDSets
  98     set(fd, none);
  99
 100     // remove client
 101     it->second->mSelector = NULL;
 102     clientMap.erase(it);
 103
 104     // recompute fdMin/fdMax if needed
 105     if (isEmpty()) {
 106         fdMin = INT_MAX;
 107         fdMax = -1;
 108     } else if (fd == fdMin) {
 109         fdMin = clientMap.begin()->first;
 110     } else if (fd == fdMax) {
 111         fdMax = clientMap.rbegin()->first;
 112     }
 113 }
 114
 115
 116 //
 117 // Adjust the FDSets for a single given Client according to a new event Type mask.
 118 //
 119 void Selector::set(int fd, Type type)
 120 {
 121     assert(fd >= 0);
 122     inSet.set(fd, type & input);
 123     outSet.set(fd, type & output);
 124     errSet.set(fd, type & critical);
 125     secdebug("selector", "fd %d notifications 0x%x", fd, type);
 126 }
 127
 128
 129 void Selector::operator () ()
 130 {
 131     if (!clientMap.empty())
 132         singleStep(0);
 133 }
 134
 135
 136 void Selector::operator () (Time::Absolute stopTime)
 137 {
 138     if (!clientMap.empty())
 139         singleStep(stopTime - Time::now());
 140 }
 141
 142
 143 //
 144 // Perform a single pass through the Selector and notify all clients
 145 // that have selected I/O pending at this time.
 146 // There is not time limit on how long this may take; if the clients
 147 // are well written, it won't be too long.
 148 //
 149 void Selector::singleStep(Time::Interval maxWait)
 150 {
 151     assert(!clientMap.empty());
 152     secdebug("selector", "select(%d) [%d-%d] for %ld clients",
 153         fdMax + 1, fdMin, fdMax, clientMap.size());
 154     for (;;) {  // pseudo-loop - only retries
 155         struct timeval duration = maxWait.timevalInterval();
 156 #if defined(__APPLE__)
 157         // ad-hoc fix: MacOS X's BSD rejects times of more than 100E6 seconds
 158         if (duration.tv_sec > 100000000)
 159             duration.tv_sec = 100000000;
 160 #endif
 161         const int size = FDSet::words(fdMax);           // number of active words in sets
 162         switch (int hits = ::select(fdMax + 1,
 163                 inSet.make(size), outSet.make(size), errSet.make(size),
 164                 &duration)) {
 165         case -1:                // error
 166             if (errno == EINTR)
 167                 continue;
 168             secdebug("selector", "select failed: errno=%d", errno);
 169             UnixError::throwMe();
 170         case 0:                 // no events
 171             secdebug("selector", "select returned nothing");
 172             return;
 173         default:                // some events
 174             secdebug("selector", "%d pending descriptors", hits);
 175             //@@@ This could be optimized as a word-merge scan.
 176             //@@@ The typical case doesn't benefit from this though, though browsers might
 177             //@@@ and integrated servers definitely would.
 178             for (int fd = fdMin; fd <= fdMax && hits > 0; fd++) {
 179                 int types = 0;
 180                 if (inSet[fd])  types |= input;
 181                 if (outSet[fd]) types |= output;
 182                 if (errSet[fd]) types |= critical;
 183                 if (types) {
 184                     secdebug("selector", "notify fd %d client %p type %d",
 185                         fd, clientMap[fd], types);
 186                     clientMap[fd]->notify(fd, types);
 187                     hits--;
 188                 }
 189             }
 190             return;
 191         }
 192     }
 193 }
 194
 195
 196 }       // end namespace IPPlusPlus
 197 }       // end namespace Security