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/**
 * Copyright 2014-2020 [fisco-dev]
 *
 * 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 org.fisco.bcos.sdk.utils;

import java.io.IOException;
import java.io.OutputStream;

/** A streaming Hex encoder. */
public class HexEncoder {
    protected final byte[] encodingTable = {
        (byte) '0', (byte) '1', (byte) '2', (byte) '3', (byte) '4', (byte) '5', (byte) '6',
                (byte) '7',
        (byte) '8', (byte) '9', (byte) 'a', (byte) 'b', (byte) 'c', (byte) 'd', (byte) 'e',
                (byte) 'f'
    };

    /*
     * set up the decoding table.
     */
    protected final byte[] decodingTable = new byte[128];

    protected void initialiseDecodingTable() {
        for (int i = 0; i < decodingTable.length; i++) {
            decodingTable[i] = (byte) 0xff;
        }

        for (int i = 0; i < encodingTable.length; i++) {
            decodingTable[encodingTable[i]] = (byte) i;
        }

        decodingTable['A'] = decodingTable['a'];
        decodingTable['B'] = decodingTable['b'];
        decodingTable['C'] = decodingTable['c'];
        decodingTable['D'] = decodingTable['d'];
        decodingTable['E'] = decodingTable['e'];
        decodingTable['F'] = decodingTable['f'];
    }

    public HexEncoder() {
        initialiseDecodingTable();
    }

    /**
     * encode the input data producing a Hex output stream.
     *
     * @param data the input byte array
     * @param off the offset of the data to be converted
     * @param length the length of the data to be converted
     * @param out the output stream
     * @throws IOException the I/O exception
     * @return the number of bytes produced.
     */
    public int encode(byte[] data, int off, int length, OutputStream out) throws IOException {
        for (int i = off; i < (off + length); i++) {
            int v = data[i] & 0xff;

            out.write(encodingTable[(v >>> 4)]);
            out.write(encodingTable[v & 0xf]);
        }

        return length * 2;
    }

    private static boolean ignore(char c) {
        return c == '\n' || c == '\r' || c == '\t' || c == ' ';
    }

    /**
     * decode the Hex encoded byte data writing it to the given output stream, whitespace characters
     * will be ignored.
     *
     * @param data the input byte array
     * @param off the offset of the data to be converted
     * @param length the length of the data to be converted
     * @param out the output stream
     * @throws IOException the I/O exception
     * @return the number of bytes produced.
     */
    public int decode(byte[] data, int off, int length, OutputStream out) throws IOException {
        byte field1, field2;
        int outLen = 0;

        int end = off + length;

        while (end > off) {
            if (!ignore((char) data[end - 1])) {
                break;
            }

            end--;
        }

        int i = off;
        while (i < end) {
            while (i < end && ignore((char) data[i])) {
                i++;
            }

            field1 = decodingTable[data[i++]];

            while (i < end && ignore((char) data[i])) {
                i++;
            }

            field2 = decodingTable[data[i++]];

            if ((field1 | field2) < 0) {
                throw new IOException("invalid characters encountered in Hex data");
            }

            out.write((field1 << 4) | (field2 & 0xff));

            outLen++;
        }

        return outLen;
    }

    /**
     * decode the Hex encoded String data writing it to the given output stream, whitespace
     * characters will be ignored.
     *
     * @param data the input byte array
     * @param out the output stream
     * @throws IOException the I/O exception
     * @return the number of bytes produced.
     */
    public int decode(String data, OutputStream out) throws IOException {
        byte b1, b2;
        int length = 0;

        int end = data.length();

        while (end > 0) {
            if (!ignore(data.charAt(end - 1))) {
                break;
            }

            end--;
        }

        int i = 0;
        while (i < end) {
            while (i < end && ignore(data.charAt(i))) {
                i++;
            }

            b1 = decodingTable[data.charAt(i++)];

            while (i < end && ignore(data.charAt(i))) {
                i++;
            }

            b2 = decodingTable[data.charAt(i++)];

            if ((b1 | b2) < 0) {
                throw new IOException("invalid characters encountered in Hex string");
            }

            out.write((b1 << 4) | (b2 & 0xff));

            length++;
        }

        return length;
    }
}