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| 1 // Copyright 2015 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 COURGETTE_CONSECUTIVE_RANGE_VISITOR_H_ |
| 6 #define COURGETTE_CONSECUTIVE_RANGE_VISITOR_H_ |
| 7 |
| 8 #include <iterator> |
| 9 |
| 10 #include "base/macros.h" |
| 11 |
| 12 namespace courgette { |
| 13 |
| 14 // Usage note: First check whether std::unique() would suffice. |
| 15 // |
| 16 // ConsecutiveRangeVisitor is a visitor to read equal consecutive items |
| 17 // ("ranges") between two iterators. The base value of InputIterator must |
| 18 // implement the == operator. |
| 19 // |
| 20 // Example: "AAAAABZZZZOO" consists of ranges ["AAAAA", "B", "ZZZZ", "OO"]. The |
| 21 // visitor provides accessors to iterate through the ranges, and to access each |
| 22 // range's value and repeat, i.e., [('A', 5), ('B', 1), ('Z', 4), ('O', 2)]. |
| 23 template <class InputIterator> |
| 24 class ConsecutiveRangeVisitor { |
| 25 public: |
| 26 ConsecutiveRangeVisitor(InputIterator begin, InputIterator end) |
| 27 : head_(begin), end_(end) { |
| 28 advance(); |
| 29 } |
| 30 |
| 31 // Returns whether there are more ranges to traverse. |
| 32 bool has_more() const { return tail_ != end_; } |
| 33 |
| 34 // Returns an iterator to an element in the current range. |
| 35 InputIterator cur() const { return tail_; } |
| 36 |
| 37 // Returns the number of repeated elements in the current range. |
| 38 size_t repeat() const { return std::distance(tail_, head_); } |
| 39 |
| 40 // Advances to the next range. |
| 41 void advance() { |
| 42 tail_ = head_; |
| 43 if (head_ != end_) |
| 44 while (++head_ != end_ && *head_ == *tail_) {} |
| 45 } |
| 46 |
| 47 private: |
| 48 InputIterator tail_; // The trailing pionter of a range (inclusive). |
| 49 InputIterator head_; // The leading pointer of a range (exclusive). |
| 50 InputIterator end_; // Store the end pointer so we know when to stop. |
| 51 |
| 52 DISALLOW_COPY_AND_ASSIGN(ConsecutiveRangeVisitor); |
| 53 }; |
| 54 |
| 55 } // namespace courgette |
| 56 |
| 57 #endif // COURGETTE_CONSECUTIVE_RANGE_VISITOR_H_ |
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