Security/libsecurity_utilities/lib/fdsel.h

   1 /*
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  10  * http://www.opensource.apple.com/apsl/ and read it before using this
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  23
  24
  25 //
  26 // fdsel - select-style file descriptor set management
  27 //
  28 #ifndef _H_FDSEL
  29 #define _H_FDSEL
  30
  31 #include <security_utilities/utilities.h>
  32 #include <sys/types.h>
  33 #include <security_utilities/debugging.h>
  34
  35
  36 namespace Security {
  37 namespace UnixPlusPlus {
  38
  39
  40 //
  41 // An FDSet object maintains a single select(2) compatible bitmap.
  42 // Size is implicitly kept by the caller (who needs to call grow() as
  43 // needed, starting at zero). As long as this is done correctly, we are
  44 // not bound by the FD_SETSIZE limit.
  45 // An FDSet can self-copy for select(2) use; after that, the [] operator
  46 // investigates the copy.
  47 //
  48 // Why are we using the FD_* macros even though we know these
  49 // are fd_mask arrays? Some implementations use optimized assembly
  50 // for these operations, and we want to pick those up.
  51 //
  52 // This whole mess is completely UNIX specific. If your system has
  53 // the poll(2) system call, ditch this and use it.
  54 //
  55 class FDSet {
  56 public:
  57     FDSet() : mBits(NULL), mUseBits(NULL) { }
  58     ~FDSet();
  59
  60     void grow(int oldWords, int newWords);
  61     void set(int fd, bool on);
  62
  63     fd_set *make(int words);
  64     bool operator [] (int fd) const     { return FD_ISSET(fd, (fd_set *)mUseBits); }
  65
  66     inline static int words(int fd)     { return (fd - 1) / NFDBITS + 1; }
  67
  68 private:
  69     fd_mask *mBits;                                     // base bits
  70     fd_mask *mUseBits;                          // mutable copy for select(2)
  71
  72     void grow(fd_mask * &bits, int oldWords, int newWords);
  73 };
  74
  75
  76 }       // end namespace UnixPlusPlus
  77 }       // end namespace Security
  78
  79
  80 #endif //_H_FDSEL