src/DescriptorSet.cc

   1 /*
   2  * DEBUG: section 05    Comm
   3  */
   4 #include "squid.h"
   5 #include "globals.h" /* for Squid_MaxFD */
   6 #include "DescriptorSet.h"
   7
   8 // pre-allocates descriptor store and index for Squid_MaxFD descriptors
   9 DescriptorSet::DescriptorSet(): descriptors_(NULL), index_(NULL),
  10         capacity_(0), size_(0)
  11 {
  12     // we allocate once and never realloc, at least for now
  13     capacity_ = Squid_MaxFD;
  14     descriptors_ = new int[capacity_];
  15     index_ = new int[capacity_];
  16
  17     // fill index with -1s to be able to say whether a descriptor is present
  18     // it is not essential to fill the descriptors, but it enables more checks
  19     for (int i = 0; i < capacity_; ++i)
  20         index_[i] = descriptors_[i] = -1;
  21 }
  22
  23 DescriptorSet::~DescriptorSet()
  24 {
  25     delete[] descriptors_;
  26     delete[] index_;
  27 }
  28
  29 /// adds if unique; returns true if added
  30 bool
  31 DescriptorSet::add(int fd)
  32 {
  33     assert(0 <= fd && fd < capacity_); // \todo: replace with Must()
  34
  35     if (has(fd))
  36         return false; // already have it
  37
  38     assert(size_ < capacity_); // \todo: replace with Must()
  39     const int pos = size_;
  40     ++size_;
  41     index_[fd] = pos;
  42     descriptors_[pos] = fd;
  43     return true; // really added
  44 }
  45
  46 /// deletes if there; returns true if deleted
  47 bool
  48 DescriptorSet::del(int fd)
  49 {
  50     assert(0 <= fd && fd < capacity_); // \todo: here and below, use Must()
  51
  52     if (!has(fd))
  53         return false; // we do not have it
  54
  55     assert(!empty());
  56     const int delPos = index_[fd];
  57     assert(0 <= delPos && delPos < capacity_);
  58
  59     // move the last descriptor to the deleted fd position
  60     // to avoid skipping deleted descriptors in pop()
  61     const int lastPos = size_-1;
  62     const int lastFd = descriptors_[lastPos];
  63     assert(delPos <= lastPos); // may be the same
  64     descriptors_[delPos] = lastFd;
  65     index_[lastFd] = delPos;
  66
  67     descriptors_[lastPos] = -1;
  68     index_[fd] = -1;
  69     --size_;
  70
  71     return true; // really added
  72 }
  73
  74 /// ejects one descriptor in unspecified order
  75 int
  76 DescriptorSet::pop()
  77 {
  78     assert(!empty());
  79     const int lastPos =--size_;
  80     const int lastFd = descriptors_[lastPos];
  81     assert(0 <= lastFd && lastFd < capacity_);
  82
  83     // cleanup
  84     descriptors_[lastPos] = -1;
  85     index_[lastFd] = -1;
  86
  87     return lastFd;
  88 }
  89
  90 void
  91 DescriptorSet::print(std::ostream &os) const
  92 {
  93     // \todo add "name" if the set is used for more than just half-closed FDs
  94     os << size_ << " FDs";
  95 }