* example this converts `☃.net` to `xn--n3h.net`, and `WwW.GoOgLe.cOm` to `www.google.com`.
 * `null` will be returned if the host cannot be ToASCII encoded or if the result contains
 * unsupported ASCII characters.
 */
internal fun String.toCanonicalHost(): String? {
  val host: String = this

  // If the input contains a :, it’s an IPv6 address.
  if (":" in host) {

 * limitations under the License.
 */
package okhttp3.internal.idn

import okio.Buffer
import okio.ByteString.Companion.encodeUtf8

/**
 * An [RFC 3492] punycode decoder for converting ASCII to Unicode domain name labels. This is
 * intended for use in Internationalized Domain Names (IDNs).
 *
 * This class contains a Kotlin implementation of the pseudocode specified by RFC 3492. It includes

        String result = DocumentUtil.encodeUrl("http://example.com/{id}");
        assertEquals("http://example.com/%7Bid%7D", result);
    }

    @Test
    public void test_encodeUrl_unicodeChars() {
        // Non-ASCII characters are percent-encoded; encoding depends on request context
        String result = DocumentUtil.encodeUrl("http://example.com/\u00D6sterreich");
        assertEquals("http://example.com/%D6sterreich", result);
    }

			// the parser is more liberal than what USTAR actually permits.
			notASCII := func(r rune) bool { return r >= 0x80 }
			if bytes.IndexFunc(tr.blk[:], notASCII) >= 0 {
				hdr.Format = FormatUnknown // Non-ASCII characters in block.
			}
			nul := func(b []byte) bool { return int(b[len(b)-1]) == 0 }
			if !(nul(v7.size()) && nul(v7.mode()) && nul(v7.uid()) && nul(v7.gid()) &&

    /** Arbitrary code point that's 4 bytes in UTF-8 and valid in IdnaMappingTable.txt. */
    private const val UNICODE_4 = 0x1d11e

    /**
     * Returns a new instance configured with a default encode set for the ASCII range. The specific
     * rules vary per-component: for example, '?' may be identity-encoded in a fragment, but must be
     * percent-encoded in a path.
     *
     * See https://url.spec.whatwg.org/#percent-encoded-bytes

                /* negotiation complete, remove the challenge object */
                ssn.removeAttribute("NtlmHttpChal");
            } else {
                final String auth = new String(Base64.decode(msg.substring(6)), "US-ASCII");
                int index = auth.indexOf(':');
                String user = index != -1 ? auth.substring(0, index) : auth;
                final String password = index != -1 ? auth.substring(index + 1) : "";

より完全な例です。

依存関係を使ってユーザー名とパスワードが正しいかを確認します。

これには、Python 標準モジュール [`secrets`](https://docs.python.org/3/library/secrets.html) を用いてユーザー名とパスワードを検証します。

`secrets.compare_digest()` は `bytes` か、ASCII 文字（英語の文字）のみを含む `str` を受け取る必要があります。つまり、`Sebastián` のように `á` を含む文字ではそのままでは動作しません。

これに対処するため、まず `username` と `password` を UTF-8 でエンコードして `bytes` に変換します。

        assertTrue(result.contains("totalAvailableEntries=5"));
        assertTrue(result.endsWith("]"));
    }

    @Test
    @DisplayName("Test readString with ASCII encoding")
    void testReadStringAscii() throws Exception {
        String testString = "TestString";
        byte[] buffer = new byte[128];
        byte[] stringBytes = testString.getBytes(StandardCharsets.US_ASCII);

        // Prepare test data with non-Unicode filename
        String expectedFilename = "asciifile.txt";
        byte[] buffer = createValidBufferNonUnicode(expectedFilename, "ASCII~1.TXT");

        // Decode
        fileBothDirectoryInfoNonUnicode.decode(buffer, 0, buffer.length);

        // Verify
        assertEquals(expectedFilename, fileBothDirectoryInfoNonUnicode.getFilename());

	x := make([]byte, 1<<20)
	// Input is ~10% space, rest ASCII non-space.
	r := rand.New(rand.NewSource(99))
	for i := range x {
		if r.Intn(10) == 0 {
			x[i] = ' '
		} else {
			x[i] = 'x'
		}
	}
	return x
}

var bytesdata = []struct {
	name string
	data []byte
}{
	{"ASCII", makeFieldsInputASCII()},
	{"Mixed", makeFieldsInput()},
}