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