net.sf.saxon.lib.DigestMaker Maven / Gradle / Ivy

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package net.sf.saxon.lib;

import net.sf.saxon.trans.UncheckedXPathException;

import java.math.BigInteger;
import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

/**
 * A wrapper around the Java cryptography classes to make a SHA-256 digest.
 * This exists so that a common API can be implemented in Java and C#.
 */
public class DigestMaker {
    private String hexDigest = null;
    private final MessageDigest digest;

    public DigestMaker() {
        try {
            digest = MessageDigest.getInstance("SHA-256");
        } catch (NoSuchAlgorithmException ex) {
            // never happens
            throw new UncheckedXPathException(ex);
        }
    }

    public void update(int value) {
        digest.update(String.valueOf(value).getBytes(StandardCharsets.UTF_8));
    }

    public void update(String value) {
        digest.update(value.getBytes(StandardCharsets.UTF_8));
    }

    public String getDigest() {
        // You can only call .digest() once
        if (hexDigest == null) {
            // Careful, don't drop leading 0's on the floor...
            hexDigest = String.format("%064x", new BigInteger(1, digest.digest()));
        }
        return hexDigest;
    }
}