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