tools/gn/deps_iterator.h

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef TOOLS_GN_DEPS_ITERATOR_H_
   6 #define TOOLS_GN_DEPS_ITERATOR_H_
   7
   8 #include "tools/gn/label_ptr.h"
   9
  10 class Target;
  11
  12 // Provides an iterator for iterating over multiple LabelTargetVectors to
  13 // make it convenient to iterate over all deps of a target.
  14 //
  15 // This works by maintaining a simple stack of vectors (since we have a fixed
  16 // number of deps types). When the stack is empty, we've reached the end. This
  17 // means that the default-constructed iterator == end() for any sequence.
  18 class DepsIterator {
  19  public:
  20   // Creates an empty iterator.
  21   DepsIterator();
  22
  23   // Iterate over the deps in the given vectors. If passing less than three,
  24   // pad with nulls.
  25   DepsIterator(const LabelTargetVector* a,
  26                const LabelTargetVector* b,
  27                const LabelTargetVector* c);
  28
  29   // Prefix increment operator. This assumes there are more items (i.e.
  30   // *this != DepsIterator()).
  31   //
  32   // For internal use, this function tolerates an initial index equal to the
  33   // length of the current vector. In this case, it will advance to the next
  34   // one.
  35   DepsIterator& operator++();
  36
  37   // Comparison for STL-based loops.
  38   bool operator!=(const DepsIterator& other) {
  39     return current_index_ != other.current_index_ ||
  40         vect_stack_[0] != other.vect_stack_[0] ||
  41         vect_stack_[1] != other.vect_stack_[1] ||
  42         vect_stack_[2] != other.vect_stack_[2];
  43   }
  44
  45   // Dereference operator for STL-compatible iterators.
  46   const LabelTargetPair& operator*() const {
  47     DCHECK_LT(current_index_, vect_stack_[0]->size());
  48     return (*vect_stack_[0])[current_index_];
  49   }
  50
  51  private:
  52   const LabelTargetVector* vect_stack_[3];
  53
  54   size_t current_index_;
  55 };
  56
  57 // Provides a virtual container implementing begin() and end() for a
  58 // sequence of deps. This can then be used in range-based for loops.
  59 class DepsIteratorRange {
  60  public:
  61   explicit DepsIteratorRange(const DepsIterator& b);
  62   ~DepsIteratorRange();
  63
  64   const DepsIterator& begin() const { return begin_; }
  65   const DepsIterator& end() const { return end_; }
  66
  67  private:
  68   DepsIterator begin_;
  69   DepsIterator end_;
  70 };
  71
  72 #endif  // TOOLS_GN_DEPS_ITERATOR_H_