1 files changed, 49 insertions, 0 deletions
diff --git a/R/pkg/src-native/string_hash_code.c b/R/pkg/src-native/string_hash_code.c
new file mode 100644
index 0000000000..e3274b9a0c
--- /dev/null
+++ b/R/pkg/src-native/string_hash_code.c
@@ -0,0 +1,49 @@
+/*
+ Licensed to the Apache Software Foundation (ASF) under one or more
+ contributor license agreements.  See the NOTICE file distributed with
+ this work for additional information regarding copyright ownership.
+ The ASF licenses this file to You under the Apache License, Version 2.0
+ (the "License"); you may not use this file except in compliance with
+ the License.  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+*/
+
+/*
+ * A C function for R extension which implements the Java String hash algorithm.
+ * Refer to http://en.wikipedia.org/wiki/Java_hashCode%28%29#The_java.lang.String_hash_function
+ *
+ */
+
+#include <R.h>
+#include <Rinternals.h>
+
+/* for compatibility with R before 3.1 */
+#ifndef IS_SCALAR
+#define IS_SCALAR(x, type) (TYPEOF(x) == (type) && XLENGTH(x) == 1)
+#endif
+
+SEXP stringHashCode(SEXP string) {
+  const char* str;
+  R_xlen_t len, i;
+  int hashCode = 0;
+  
+  if (!IS_SCALAR(string, STRSXP)) {
+    error("invalid input");
+  }
+  
+  str = CHAR(asChar(string));
+  len = XLENGTH(asChar(string));
+  
+  for (i = 0; i < len; i++) {
+    hashCode = (hashCode << 5) - hashCode + *str++;
+  }
+
+  return ScalarInteger(hashCode);
+}