1 files changed, 75 insertions, 0 deletions
diff --git a/extractor/suffix_array.h b/extractor/suffix_array.h
new file mode 100644
index 00000000..bf731d79
--- /dev/null
+++ b/extractor/suffix_array.h
@@ -0,0 +1,75 @@
+#ifndef _SUFFIX_ARRAY_H_
+#define _SUFFIX_ARRAY_H_
+
+#include <memory>
+#include <string>
+#include <vector>
+
+#include <boost/filesystem.hpp>
+
+namespace fs = boost::filesystem;
+using namespace std;
+
+namespace extractor {
+
+class DataArray;
+class PhraseLocation;
+
+class SuffixArray {
+ public:
+  // Creates a suffix array from a data array.
+  SuffixArray(shared_ptr<DataArray> data_array);
+
+  virtual ~SuffixArray();
+
+  // Returns the size of the suffix array.
+  virtual int GetSize() const;
+
+  // Returns the data array on top of which the suffix array is constructed.
+  virtual shared_ptr<DataArray> GetData() const;
+
+  // Constructs the longest-common-prefix array using the algorithm of Kasai et
+  // al. (2001).
+  virtual vector<int> BuildLCPArray() const;
+
+  // Returns the i-th suffix.
+  virtual int GetSuffix(int rank) const;
+
+  // Given the range in which a phrase is located and the next word, returns the
+  // range corresponding to the phrase extended with the next word.
+  virtual PhraseLocation Lookup(int low, int high, const string& word,
+                                int offset) const;
+
+  void WriteBinary(const fs::path& filepath) const;
+
+ protected:
+  SuffixArray();
+
+ private:
+  // Constructs the suffix array using the algorithm of Larsson and Sadakane
+  // (1999).
+  void BuildSuffixArray();
+
+  // Bucket sort on the data array (used for initializing the construction of
+  // the suffix array.)
+  void InitialBucketSort(vector<int>& groups);
+
+  void TernaryQuicksort(int left, int right, int step, vector<int>& groups);
+
+  // Constructs the suffix array in log(n) steps by doubling the length of the
+  // suffixes at each step.
+  void PrefixDoublingSort(vector<int>& groups);
+
+  // Given a [low, high) range in the suffix array in which all elements have
+  // the first offset-1 values the same, it returns the first position where the
+  // offset value is greater or equal to word_id.
+  int LookupRangeStart(int low, int high, int word_id, int offset) const;
+
+  shared_ptr<DataArray> data_array;
+  vector<int> suffix_array;
+  vector<int> word_start;
+};
+
+} // namespace extractor
+
+#endif