src/DescriptorSet.cc

   1 /*
   2  * Copyright (C) 1996-2015 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 /* DEBUG: section 05    Comm */
  10
  11 #include "squid.h"
  12 #include "DescriptorSet.h"
  13 #include "globals.h" /* for Squid_MaxFD */
  14
  15 // pre-allocates descriptor store and index for Squid_MaxFD descriptors
  16 DescriptorSet::DescriptorSet(): descriptors_(NULL), index_(NULL),
  17     capacity_(0), size_(0)
  18 {
  19     // we allocate once and never realloc, at least for now
  20     capacity_ = Squid_MaxFD;
  21     descriptors_ = new int[capacity_];
  22     index_ = new int[capacity_];
  23
  24     // fill index with -1s to be able to say whether a descriptor is present
  25     // it is not essential to fill the descriptors, but it enables more checks
  26     for (int i = 0; i < capacity_; ++i)
  27         index_[i] = descriptors_[i] = -1;
  28 }
  29
  30 DescriptorSet::~DescriptorSet()
  31 {
  32     delete[] descriptors_;
  33     delete[] index_;
  34 }
  35
  36 /// adds if unique; returns true if added
  37 bool
  38 DescriptorSet::add(int fd)
  39 {
  40     assert(0 <= fd && fd < capacity_); // \todo: replace with Must()
  41
  42     if (has(fd))
  43         return false; // already have it
  44
  45     assert(size_ < capacity_); // \todo: replace with Must()
  46     const int pos = size_;
  47     ++size_;
  48     index_[fd] = pos;
  49     descriptors_[pos] = fd;
  50     return true; // really added
  51 }
  52
  53 /// deletes if there; returns true if deleted
  54 bool
  55 DescriptorSet::del(int fd)
  56 {
  57     assert(0 <= fd && fd < capacity_); // \todo: here and below, use Must()
  58
  59     if (!has(fd))
  60         return false; // we do not have it
  61
  62     assert(!empty());
  63     const int delPos = index_[fd];
  64     assert(0 <= delPos && delPos < capacity_);
  65
  66     // move the last descriptor to the deleted fd position
  67     // to avoid skipping deleted descriptors in pop()
  68     const int lastPos = size_-1;
  69     const int lastFd = descriptors_[lastPos];
  70     assert(delPos <= lastPos); // may be the same
  71     descriptors_[delPos] = lastFd;
  72     index_[lastFd] = delPos;
  73
  74     descriptors_[lastPos] = -1;
  75     index_[fd] = -1;
  76     --size_;
  77
  78     return true; // really added
  79 }
  80
  81 /// ejects one descriptor in unspecified order
  82 int
  83 DescriptorSet::pop()
  84 {
  85     assert(!empty());
  86     const int lastPos =--size_;
  87     const int lastFd = descriptors_[lastPos];
  88     assert(0 <= lastFd && lastFd < capacity_);
  89
  90     // cleanup
  91     descriptors_[lastPos] = -1;
  92     index_[lastFd] = -1;
  93
  94     return lastFd;
  95 }
  96
  97 void
  98 DescriptorSet::print(std::ostream &os) const
  99 {
 100     // \todo add "name" if the set is used for more than just half-closed FDs
 101     os << size_ << " FDs";
 102 }
 103