import (
	"crypto/md5"
	"encoding/hex"

	"github.com/minio/minio/internal/hash/sha256"
)

// getSHA256Hash returns SHA-256 hash in hex encoding of given data.
func getSHA256Hash(data []byte) string {
	return hex.EncodeToString(getSHA256Sum(data))
}

// getSHA256Hash returns SHA-256 sum of given data.
func getSHA256Sum(data []byte) []byte {
	hash := sha256.New()
	hash.Write(data)
	return hash.Sum(nil)
}

                        while (buffer[bufferIndex + len] != (byte) 0x00 || buffer[bufferIndex + len + 1] != (byte) 0x00) {
                            len += 2;
                            if (len > 256) {
                                throw new RuntimeException("zero termination not found");
                            }
                        }

        assertEquals(2048, result.length()); // 1024 bytes * 2 chars

        // Test partial conversion
        String partial = Hexdump.toHexString(data, 512, 256);
        assertEquals(512, partial.length()); // 256 bytes * 2 chars
        assertTrue(partial.startsWith("00010203")); // 512 % 256 = 0, so starts at 0
    }

    fun X509Certificate.sha256Hash(): ByteString = publicKey.encoded.toByteString().sha256()

    /**
     * Returns the SHA-256 of `certificate`'s public key.
     *
     * In OkHttp 3.1.2 and earlier, this returned a SHA-1 hash of the public key. Both types are
     * supported, but SHA-256 is preferred.
     */
    @JvmStatic
    fun pin(certificate: Certificate): String {

This is based on RFC 4253, section 6.4, but with hmac-md5 variants removed because they have 
reached the end of their useful life.

Valid values: 

```
hmac-sha2-256******@****.***
******@****.***
hmac-sha2-256
hmac-sha2-512
hmac-sha1
hmac-sha1-96
```

### Certificate-based authentication

  private static final int CRC32C_GENERATOR_FLIPPED = Integer.reverse(CRC32C_GENERATOR);

  public void testCrc32cByteTable() {
    // See Hacker's Delight 2nd Edition, Figure 14-7.
    int[] expected = new int[256];
    for (int i = 0; i < expected.length; i++) {
      int crc = i;
      for (int j = 7; j >= 0; j--) {
        int mask = -(crc & 1);
        crc = (crc >>> 1) ^ (CRC32C_GENERATOR_FLIPPED & mask);
      }

    }

    @Test
    void testReadLength_LongForm() throws IOException {
        // Definite-length long form (length 256)
        InputStream s = new ByteArrayInputStream(new byte[] { (byte) 0x82, 0x01, 0x00 });
        int length = ASN1Util.readLength(s, 500, false);
        assertEquals(256, length);
    }

    @Test
    void testReadLength_Indefinite() throws IOException {
        // Indefinite-length

    assertEquals(8581389452482819506L, fingerprint("test".getBytes(UTF_8)));
    // 32 characters long
    assertEquals(-4196240717365766262L, fingerprint(Strings.repeat("test", 8).getBytes(UTF_8)));
    // 256 characters long
    assertEquals(3500507768004279527L, fingerprint(Strings.repeat("test", 64).getBytes(UTF_8)));
  }

  public void testStringsConsistency() {

/**
 * Benchmarks for comparing instance creation of {@link MessageDigest}s.
 *
 * @author Kurt Alfred Kluever
 */
@NullUnmarked
public class MessageDigestCreationBenchmark {

  @Param({"MD5", "SHA-1", "SHA-256", "SHA-384", "SHA-512"})
  private String algorithm;

  private MessageDigest md;

  @BeforeExperiment
  void setUp() throws Exception {
    md = MessageDigest.getInstance(algorithm);
  }

  @Benchmark

        assertEquals("31f30ddbcb1bf8446576f0e64aa4c88a9f055e3c", MessageDigestUtil.digest("SHA-1", text));
        assertEquals("ecb666d778725ec97307044d642bf4d160aabb76f56c0069c71ea25b1e926825", MessageDigestUtil.digest("SHA-256", text));

        try {
            MessageDigestUtil.digest(null, text);
            assertTrue(false);
        } catch (final EmptyArgumentException e) {
            assertTrue(true);
        }
        try {