com.google.security.wycheproof.JsonUtil.java Source code

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Here is the source code for com.google.security.wycheproof.JsonUtil.java

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/**
 * Licensed 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.
 */
package com.google.security.wycheproof;

import static java.nio.charset.StandardCharsets.UTF_8;

import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import com.google.gson.JsonParseException;
import com.google.gson.JsonParser;
import com.google.gson.stream.JsonReader;
import java.io.FileInputStream;
import java.io.InputStreamReader;
import java.io.IOException;
import java.math.BigInteger;

/** Utilities for reading test vectors in JSON format */
public class JsonUtil {

    /**
     * Reads a set of test vectors from a file.
     * @param filename the name of the file, local to the directory with the
     *        the test vectors.
     * @return a JsonObject with a test
     * @throws IOException if the test vectors could not be read.
     * @throws JsonParseException if the file is not valid JSON.
     */
    public static JsonObject getTestVectors(String filename) throws IOException {
        // The directory where the test vectors are.
        String testVectorsDir = "testvectors/";
        FileInputStream is = new FileInputStream(testVectorsDir + filename);
        JsonReader reader = new JsonReader(new InputStreamReader(is, UTF_8));
        JsonParser parser = new JsonParser();
        JsonElement elem = parser.parse(reader);
        return elem.getAsJsonObject();
    }

    /** 
     * Converts a JsonElement into a byte array.
     * @param element a JsonElement containing an encoded byte array. 
     *        Wycheproof represents byte arrays as hexadeciamal strings.
     * @throws ClassCastException if element is not a valid string value.
     * @throws IllegalStateException - if element contains an array.
     */
    public static byte[] asByteArray(JsonElement element) {
        String hex = element.getAsString();
        return TestUtil.hexToBytes(hex);
    }

    /**
     * Converts a JsonElement into a BigInteger.
     * @param element a JsonElement containing a BigInteger. 
     * Wycheproof represents BigIntegers as hexadecimal strings using
     * twos complement representation.
     * <p> E.g., 31 is represented as "1f", -1 is represented as "f", and
     * 255 is represented as "0ff".
     * @throws ClassCastException if element is not a valid string value.
     * @throws IllegalStateException if element contains an array.
     * @throws NumberFormatException if representation of the BigInteger is invalid.
     */
    public static BigInteger asBigInteger(JsonElement element) {
        String hex = element.getAsString();
        // TODO(bleichen): Consider to change the representation of BigIntegers in
        //   Wycheproof as hexadecimal string with a sign.
        if (hex.length() % 2 == 1) {
            if (hex.charAt(0) >= '0' && hex.charAt(0) <= '7') {
                hex = "0" + hex;
            } else {
                hex = "f" + hex;
            }
        }
        return new BigInteger(TestUtil.hexToBytes(hex));
    }
}