### Read and Write SquashFS Filesystem Example

Source: https://docs.rs/backhand/0.25.1/src/backhand/lib.rs.html

This example demonstrates reading an existing SquashFS image, converting it to a writer, adding new files, replacing an existing file, and writing the modified filesystem to a new file. Ensure you have a file named 'file.squashfs' and 'dune' to run this example.

```rust
# use std::fs::File;
# use std::io::{Cursor, BufReader};
# use backhand::{FilesystemReader, FilesystemWriter, NodeHeader};
// read
let file = BufReader::new(File::open("file.squashfs").unwrap());
let read_filesystem = FilesystemReader::from_reader(file).unwrap();

// convert to writer
let mut write_filesystem = FilesystemWriter::from_fs_reader(&read_filesystem).unwrap();

// add file with data from slice
let d = NodeHeader::default();
let bytes = Cursor::new(b"Fear is the mind-killer.");
write_filesystem.push_file(bytes, "a/d/e/new_file", d);

// add file with data from file
let new_file = File::open("dune").unwrap();
write_filesystem.push_file(new_file, "/root/dune", d);

// replace a existing file
let bytes = Cursor::new(b"The sleeper must awaken.\n");
write_filesystem
    .replace_file("/a/b/c/d/e/first_file", bytes)
    .unwrap();

// write into a new file
let mut output = File::create("modified.squashfs").unwrap();
write_filesystem.write(&mut output).unwrap();

```

--------------------------------

### FilesystemReader Usage Example

Source: https://docs.rs/backhand/0.25.1/backhand/v3/filesystem/reader/struct.FilesystemReader.html

Example demonstrating how to extract files using FilesystemReader.

```APIDOC
## Example Usage of FilesystemReader

### Description
This example shows how to iterate through files in a filesystem and extract them using `FilesystemReaderFile`.

### Method
N/A (Illustrative Example)

### Endpoint
N/A

### Parameters
N/A

### Request Example
```rust
// [snip: creating FilesystemReader]

for node in filesystem.files() {
    // extract
    match &node.inner {
        InnerNode::File(file) => {
            let mut reader = filesystem
                .file(&file)
                .reader();
            // Then, do something with the reader
        },
        _ => (),
    }
}
```

### Response
N/A
```