src/DescriptorSet.h

   1 /*
   2  * Copyright (C) 1996-2023 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 /* TODO: Should we use std::set<int> with its flexibility? Our implementation
  15     has constant overhead, which is smaller than log(n) of std::set.
  16 */
  17 /// An unordered collection of unique descriptors with O(1) add/del/has ops
  18 class DescriptorSet
  19 {
  20 public:
  21     // for STL compatibility, should we decide to switch to std::set or similar
  22     typedef const int *const_iterator;
  23
  24     DescriptorSet();
  25     ~DescriptorSet();
  26
  27     /// checks whether fd is in the set
  28     bool has(const int fd) const {
  29         return 0 <= fd && fd < capacity_ &&
  30                index_[fd] >= 0;
  31     }
  32
  33     bool add(int fd); ///< adds if unique; returns true if added
  34     bool del(int fd); ///< deletes if there; returns true if deleted
  35     int pop(); ///< deletes and returns one descriptor, in unspecified order
  36
  37     bool empty() const { return !size_; } ///< number of descriptors in the set
  38
  39     /// begin iterator a la STL; may become invalid if the object is modified
  40     const_iterator begin() const { return descriptors_; }
  41     /// end iterator a la STL; may become invalid if the object is modified
  42     const_iterator end() const { return begin() + size_; }
  43
  44     /// outputs debugging info about the set
  45     void print(std::ostream &os) const;
  46
  47 private:
  48     // these would be easy to support when needed; prohibit for now
  49     DescriptorSet(const DescriptorSet &s); // declared but undefined
  50     DescriptorSet &operator =(const DescriptorSet &s); // declared, undefined
  51
  52     int *descriptors_; ///< descriptor values in random order
  53     int *index_; ///< descriptor:position index into descriptors_
  54     int capacity_; ///< total number of descriptor slots
  55     int size_; ///< number of descriptors in the set
  56 };
  57
  58 /// convenience wrapper to be used in debugs() context
  59 inline std::ostream &
  60 operator <<(std::ostream &os, const DescriptorSet &ds)
  61 {
  62     ds.print(os);
  63     return os;
  64 }
  65
  66 #endif /* SQUID_DESCRIPTOR_SET_H */
  67