cdsa/cdsa_utilities/fdsel.h

   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 // fdsel - select-style file descriptor set management
  21 //
  22 #ifndef _H_FDSEL
  23 #define _H_FDSEL
  24
  25 #include <Security/utilities.h>
  26 #include <sys/types.h>
  27 #include <Security/debugging.h>
  28
  29
  30 namespace Security {
  31 namespace UnixPlusPlus {
  32
  33
  34 //
  35 // An FDSet object maintains a single select(2) compatible bitmap.
  36 // Size is implicitly kept by the caller (who needs to call grow() as
  37 // needed, starting at zero). As long as this is done correctly, we are
  38 // not bound by the FD_SETSIZE limit.
  39 // An FDSet can self-copy for select(2) use; after that, the [] operator
  40 // investigates the copy.
  41 //
  42 // Why are we using the FD_* macros even though we know these
  43 // are fd_mask arrays? Some implementations use optimized assembly
  44 // for these operations, and we want to pick those up.
  45 //
  46 // This whole mess is completely UNIX specific. If your system has
  47 // the poll(2) system call, ditch this and use it.
  48 //
  49 class FDSet {
  50 public:
  51     FDSet() : mBits(NULL), mUseBits(NULL) { }
  52     ~FDSet();
  53
  54     void grow(int oldWords, int newWords);
  55     void set(int fd, bool on);
  56
  57     fd_set *make(int words);
  58     bool operator [] (int fd) const     { return FD_ISSET(fd, (fd_set *)mUseBits); }
  59
  60     inline static int words(int fd)     { return (fd - 1) / NFDBITS + 1; }
  61
  62 private:
  63     fd_mask *mBits;                                     // base bits
  64     fd_mask *mUseBits;                          // mutable copy for select(2)
  65
  66     void grow(fd_mask * &bits, int oldWords, int newWords);
  67 };
  68
  69
  70 }       // end namespace UnixPlusPlus
  71 }       // end namespace Security
  72
  73
  74 #endif //_H_FDSEL