# Tutorial - User Guide { #tutorial-user-guide }

This tutorial shows you how to use **FastAPI** with most of its features, step by step.

Each section gradually builds on the previous ones, but it's structured to separate topics, so that you can go directly to any specific one to solve your specific API needs.

It is also built to work as a future reference so you can come back and see exactly what you need.

## Run the code { #run-the-code }

    * Because pydantic data structures are just instances of classes you define; auto-completion, linting, mypy and your intuition should all work properly with your validated data.
* Validate **complex structures**:
    * Use of hierarchical Pydantic models, Python `typing`’s `List` and `Dict`, etc.

     */
    public void processChangeNotification(ChangeNotificationHandle handle, byte[] outputBuffer) {
        if (outputBuffer == null || outputBuffer.length == 0) {
            return;
        }

        int offset = 0;

        while (offset < outputBuffer.length) {
            // Parse FILE_NOTIFY_INFORMATION structure

- Nested archive extraction

#### Web and Markup
- HTML, XHTML with XPath support
- XML documents
- JSON and structured data

#### Media Files
- Audio formats (MP3, WAV, FLAC)
- Video formats (MP4, AVI, MOV)
- Metadata extraction from media files

## Architecture

### Multi-Module Structure

```
fess-crawler-parent/
├── fess-crawler/              # Core crawler framework

        assertEquals(0, bytesWritten);
    }

    @Test
    @DisplayName("Should handle error response structure size 9")
    void testReadBytesWireFormatErrorResponse() throws Exception {
        // Given
        byte[] buffer = new byte[256];
        int bufferIndex = 0;

        // Write structure size (9) - indicates error response
        SMBUtil.writeInt2(9, buffer, bufferIndex);

This way, its schema will show up in the API docs user interface:

<img src="/img/tutorial/dataclasses/image01.png">

## Dataclasses in Nested Data Structures { #dataclasses-in-nested-data-structures }

You can also combine `dataclasses` with other type annotations to make nested data structures.

        byte[] buffer = new byte[512];
        int offset = 0;

        // Set header start position for the response
        setHeaderStart(response, 64);

        // Write structure header (9 bytes)
        SMBUtil.writeInt2(9, buffer, offset); // Structure size
        SMBUtil.writeInt2(80 - 64, buffer, offset + 2); // Buffer offset (relative to header)
        SMBUtil.writeInt4(50, buffer, offset + 4); // Total length of notification data

 */
package jcifs.internal.smb2.rdma;

import jcifs.internal.util.SMBUtil;

/**
 * SMB2 RDMA Transform structure for READ/WRITE channel info.
 *
 * As per MS-SMB2 2.2.13.1.1 and 2.2.21.1.1
 */
public class Smb2RdmaTransform {

    // SMB_DIRECT_BUFFER_DESCRIPTOR_V1 structure
    private long offset; // 8 bytes: Offset within registered buffer
    private int token; // 4 bytes: RDMA provider token

import org.codelibs.fess.unit.UnitFessTestCase;

public class FessWebResourceRootTest extends UnitFessTestCase {

    public void test_classExists() {
        // Basic test to verify the class exists and has the correct structure
        assertNotNull("FessWebResourceRoot class should exist", FessWebResourceRoot.class);
    }

    public void test_inheritance() {
        // Verify that FessWebResourceRoot extends StandardRoot

    }

    /**
     * Creates a basic negotiate response buffer with minimum valid structure.
     */
    private byte[] createBasicNegotiateResponseBuffer() {
        byte[] buffer = new byte[300]; // Sufficient size for basic structure + offsets

        // Structure size (65)
        SMBUtil.writeInt2(65, buffer, 0);

        // Security mode