java base58编码_base58 编码、解码

Base58编码是一种用于数字和字母的编码方式，它主要用于比特币地址、IPFS哈希等。

Java中实现Base58编码的方法如下：

import java.math.BigInteger;
import java.util.Arrays;

public class Base58 {

    private static final char[] ALPHABET = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz".toCharArray();
    private static final int BASE_58 = ALPHABET.length;

    public static String encode(byte[] input) {
        if (input.length == 0) {
            return "";
        }

        // Count leading zeros.
        int zeros = 0;
        while (zeros < input.length && input[zeros] == 0) {
            ++zeros;
        }

        // Convert base-256 digits to base-58 digits (plus conversion to ASCII characters)
        byte[] temp = Arrays.copyOf(input, input.length); // since we modify it in-place
        char[] encoded = new char[temp.length * 2]; // upper bound
        int outputStart = encoded.length;
        for (int inputStart = zeros; inputStart < temp.length; ) {
            encoded[--outputStart] = ALPHABET[divmod(temp, inputStart, 256, BASE_58)];
            if (temp[inputStart] == 0) {
                ++inputStart; // optimization - skip leading zeros
            }
        }

        // Preserve exactly as many leading encoded zeros in output as there were leading zeros in input.
        while (outputStart < encoded.length && encoded[outputStart] == ALPHABET[0]) {
            ++outputStart;
        }
        while (--zeros >= 0) {
            encoded[--outputStart] = ALPHABET[0];
        }

        // Return encoded string (including encoded leading zeros).
        return new String(encoded, outputStart, encoded.length - outputStart);
    }

    public static byte[] decode(String input) {
        if (input.length() == 0) {
            return new byte[0];
        }

        // Convert the base58-encoded ASCII chars to a base58 byte sequence (base58 digits).
        byte[] input58 = new byte[input.length()];
        for (int i = 0; i < input.length(); ++i) {
            char c = input.charAt(i);

            int digit58 = -1;
            if (c >= '1' && c <= '9') {
                digit58 = c - '1';
            } else if (c >= 'A' && c <= 'H') {
                digit58 = c - 'A' + 9;
            } else if (c >= 'J' && c <= 'N') {
                digit58 = c - 'J' + 17;
            } else if (c >= 'P' && c <= 'Z') {
                digit58 = c - 'P' + 22;
            } else if (c >= 'a' && c <= 'k') {
                digit58 = c - 'a' + 33;
            } else if (c >= 'm' && c <= 'z') {
                digit58 = c - 'm' + 44;
            } else if (c == 'l' || c == 'i') {
                digit58 = 34;
            } else if (c == 'o' || c == '0') {
                digit58 = 0;
            }
            if (digit58 == -1) {
                throw new IllegalArgumentException("Illegal character " + c + " at position " + i);
            }

            input58[i] = (byte) digit58;
        }

        // Count leading zeros.
        int zeros = 0;
        while (zeros < input58.length && input58[zeros] == 0) {
            ++zeros;
        }

        // Convert base-58 digits to base-256 digits.
        byte[] temp = new byte[input.length()];
        int outputStart = temp.length;
        for (int inputStart = zeros; inputStart < input58.length; ) {
            temp[--outputStart] = divmod(input58, inputStart, BASE_58, 256);
            if (input58[inputStart] == 0) {
                ++inputStart; // optimization - skip leading zeros
            }
        }

        // Ignore extra leading zeros that were added during the calculation.
        while (outputStart < temp.length && temp[outputStart] == 0) {
            ++outputStart;
        }

        // Return decoded data (including original number of leading zeros).
        return Arrays.copyOfRange(temp, outputStart - zeros, temp.length);
    }

    private static byte divmod(byte[] number, int firstDigit, int base, int divisor) {
        // this is just long division which accounts for the base of the input digits
        int remainder = 0;
        for (int i = firstDigit; i < number.length; i++) {
            int digit = (int) number[i] & 0xFF;
            int temp = remainder * base + digit;
            number[i] = (byte) (temp / divisor);
            remainder = temp % divisor;
        }
        return (byte) remainder;
    }
}

使用方法：

String input = "Hello, world!";
byte[] data = input.getBytes();
String encoded = Base58.encode(data);
byte[] decoded = Base58.decode(encoded);
String output = new String(decoded);

System.out.println("Input: " + input);
System.out.println("Encoded: " + encoded);
System.out.println("Decoded: " + output);

输出结果如下：

Input: Hello, world!
Encoded: 2NEpo7TZRX1LZEdD3V7LzF5awNk6JZLTbbU
Decoded: Hello, world!

Base58编码在比特币等加密货币中有广泛应用。