## Version 5.0.0-alpha.4

_2022-02-01_

**This release introduces fast fallback to better support mixed IPv4+IPv6 networks.** Fast fallback
is what we're calling our implementation of Happy Eyeballs, [RFC 8305][rfc_8305]. With this
feature OkHttp will attempt both IPv6 and IPv4 connections concurrently, keeping whichever connects
first. Fast fallback gives IPv6 connections a 250 ms head start so IPv6 is preferred on networks

import okio.BufferedSource

/**
 * [HTTP/2][Protocol.HTTP_2] only. Processes server-initiated HTTP requests on the client.
 * Implementations must quickly dispatch callbacks to avoid creating a bottleneck.
 *
 * While [onReset] may occur at any time, the following callbacks are expected in order,
 * correlated by stream ID.
 *
 *  * [onRequest]
 *  * [onHeaders] (unless canceled)
 *  * [onData] (optional sequence of data frames)
 *

        nestedMap.put("outer", Maps.map("inner", "value").$());
        assertEquals(183L, MemoryUtil.sizeOf(nestedMap));
    }

    public void test_sizeOf_customObjects() {
        // Test fallback case for custom objects (should return 16L)
        assertEquals(16L, MemoryUtil.sizeOf(new Object()));
        assertEquals(16L, MemoryUtil.sizeOf(new CustomTestObject()));

        assertNotNull(firstName, "First called name should not be null");
    }

    @Test
    @DisplayName("nextCalledName should return valid name for fallback attempts")
    void testNextCalledNameContract() {
        // Given
        String expectedNextName = "SERVER15";
        when(mockAddress.nextCalledName(mockContext)).thenReturn(expectedNextName);

        // When

        assertEquals("share/", b.getName());

        // host when no path/share
        SmbResourceLocatorImpl c = locator("smb://server/");
        assertEquals("server/", c.getName());

        // root fallback
        SmbResourceLocatorImpl d = locator("smb:///");
        assertEquals("smb://", d.getName());
    }

    @Test
    @DisplayName("Parent URL is computed correctly")
    void testGetParent() {

        // Test cleanup
        region.close();
        assertFalse(region.isValid(), "Region should be invalid after close");
    }

    @Test
    public void testGetProviderName() {
        assertEquals("TCP Fallback", provider.getProviderName());
    }

    @Test
    public void testGetMaxMessageSize() {
        assertEquals(65536, provider.getMaxMessageSize(), "TCP provider should have 64KB limit");
    }

    @Test

    )

  println("TLS1.3+TLS1.2")
  testClient(urls, buildClient(ConnectionSpec.RESTRICTED_TLS))

  println("\nTLS1.3 only")
  testClient(urls, buildClient(TLS_13))

  println("\nTLS1.3 then fallback")
  testClient(urls, buildClient(TLS_13, TLS_12))

     *
     * Use this API to attach timing, debugging, or other application data to a request so that
     * you may read it in interceptors, event listeners, or callbacks.
     */
    @JvmName("reifiedTag")
    inline fun <reified T : Any> tag(tag: T?): Builder = tag(T::class, tag)

    /**

        // Try providers in order of preference
        List<RdmaProvider> providers = Arrays.asList(new DisniRdmaProvider(), // InfiniBand/RoCE - highest performance
                new TcpRdmaProvider() // TCP fallback - always available
        );

        for (RdmaProvider provider : providers) {
            if (provider.isAvailable()) {
                log.info("Selected RDMA provider: {}", provider.getProviderName());

            // we called sizeIfKnown and when we started reading the file (or I guess if
            // maxCharsPerByte is wrong)
            // Fallback to an incremental approach
            StringBuilder builder = new StringBuilder(bufIndex + 32);
            builder.append(buffer, 0, bufIndex);
            buffer = null; // release for gc