Add get_word_id(char* word) method to library

Change-Id: Idf0701248ccdf0ecc1c2265d215fbe582510ea96
diff --git a/src/collocatordb.cc b/src/collocatordb.cc
index 691f820..352efd3 100644
--- a/src/collocatordb.cc
+++ b/src/collocatordb.cc
@@ -327,6 +327,8 @@
                                             void readVocab(string fname);
                                             string getWord(uint32_t w1);
 
+                                            uint64_t getWordId(const char *word) const;
+
                                             CollocatorDB(const char *db_name, bool read_only);
 
                                             // public interface of CollocatorDB.
@@ -794,6 +796,14 @@
   return _vocab[w1].word;
 }
 
+uint64_t rocksdb::CollocatorDB::getWordId(const char *word) const {
+  for (uint64_t i = 0; i < _vocab.size(); i++) {
+    if (strcmp(_vocab[i].word.c_str(), word) == 0)
+      return i;
+  }
+  return 0;
+}
+
 string rocksdb::CollocatorDB::collocators2json(uint32_t w1, vector<Collocator> collocators) {
   ostringstream s;
   int i = 0;
@@ -883,6 +893,10 @@
     return strdup(db->getWord(w).c_str());
   }
 
+  DLL_EXPORT uint64_t get_word_id(COLLOCATORS *db, char *word) {
+    return db->getWordId(word);
+  }
+
   DLL_EXPORT void read_vocab(COLLOCATORS *db, char *fname) {
     std::string fName(fname);
     db->readVocab(fName);