src/DescriptorSet.h

   1 /*
   2  * Copyright (C) 1996-2018 The Squid Software Foundation and contributors
   3  *
   4  * Squid software is distributed under GPLv2+ license and includes
   5  * contributions from numerous individuals and organizations.
   6  * Please see the COPYING and CONTRIBUTORS files for details.
   7  */
   8
   9 #ifndef SQUID_DESCRIPTOR_SET_H
  10 #define SQUID_DESCRIPTOR_SET_H
  11
  12 #include <iosfwd>
  13
  14 /** \ingroup Comm
  15
  16     \todo: Should we use std::set<int> with its flexibility? Our implementation
  17     has constant overhead, which is smaller than log(n) of std::set.
  18
  19 an unordered collection of unique descriptors with O(1) add/del/has ops */
  20 class DescriptorSet
  21 {
  22 public:
  23     // for STL compatibility, should we decide to switch to std::set or similar
  24     typedef const int *const_iterator;
  25
  26     DescriptorSet();
  27     ~DescriptorSet();
  28
  29     /// checks whether fd is in the set
  30     bool has(const int fd) const {
  31         return 0 <= fd && fd < capacity_ &&
  32                index_[fd] >= 0;
  33     }
  34
  35     bool add(int fd); ///< adds if unique; returns true if added
  36     bool del(int fd); ///< deletes if there; returns true if deleted
  37     int pop(); ///< deletes and returns one descriptor, in unspecified order
  38
  39     bool empty() const { return !size_; } ///< number of descriptors in the set
  40
  41     /// begin iterator a la STL; may become invalid if the object is modified
  42     const_iterator begin() const { return descriptors_; }
  43     /// end iterator a la STL; may become invalid if the object is modified
  44     const_iterator end() const { return begin() + size_; }
  45
  46     /// outputs debugging info about the set
  47     void print(std::ostream &os) const;
  48
  49 private:
  50     // these would be easy to support when needed; prohibit for now
  51     DescriptorSet(const DescriptorSet &s); // declared but undefined
  52     DescriptorSet &operator =(const DescriptorSet &s); // declared, undefined
  53
  54     int *descriptors_; ///< descriptor values in random order
  55     int *index_; ///< descriptor:position index into descriptors_
  56     int capacity_; ///< total number of descriptor slots
  57     int size_; ///< number of descriptors in the set
  58 };
  59
  60 /// convenience wrapper to be used in debugs() context
  61 inline std::ostream &
  62 operator <<(std::ostream &os, const DescriptorSet &ds)
  63 {
  64     ds.print(os);
  65     return os;
  66 }
  67
  68 #endif /* SQUID_DESCRIPTOR_SET_H */
  69