You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: decompress.rs
    path of file: ./repos/remacs/rust_src/src
    
    the code of the file until where you have to start completion: //! Interface to zlib.
use std::cmp::min;
use std::io::prelude::Read;
use std::slice;

use flate2::read::{DeflateDecoder, GzDecoder, ZlibDecoder};
use remacs_macros::lisp_fn;

use crate::{
    buffers::validate_region_rust,
    lisp::LispObject,
    remacs_sys::{
        del_range_2, insert_from_gap, make_gap, maybe_quit, modify_text, move_gap_both,
        signal_after_change, update_compositions, CHECK_HEAD,
    },
    threads::ThreadState,
};

/// Return t if zlib decompression is available in this instance of Emacs.
#[lisp_fn]
pub fn zlib_available_p() -> bool {
    true
}

fn create_buffer_decoder<'a>(buffer: &'a [u8]) -> Box<dyn Read + 'a> {
    let magic_number = buffer[0];

    match magic_number {
        // Zlib
        0x78 => Box::new(ZlibDecoder::new(buffer)),
        // Gzlib
        0x1F => Box::new(GzDecoder::new(buffer)),
        // Assume the data is raw, if neither zlib nor gzib header can be found.
        _ => Box::new(DeflateDecoder::new(buffer)),
    }
}

/// Decompress a gzip- or zlib-compressed region.
/// Replace the text in the region by the decompressed data.
/// On failure, return nil and leave the data in place.
/// This function can be called only in unibyte buffers.
#[lisp_fn]
pub fn zlib_decompress_region(start: LispObject, end: LispObject) -> bool {
    let (start, end) = validate_region_rust(start, end);

    let mut current_buffer = ThreadState::current_buffer_unchecked();

    if current_buffer.multibyte_characters_enabled() {
        error!("This function can be called only in unibyte buffers");
    };

    // Empty region, decompress failed.
    if start == end {
        return false;
    }

    unsafe {
        // Do the following before manipulating the gap.
        modify_text(start, end);

        move_gap_both(end, end);
    }

    // Insert the decompressed data at the end of the compressed data.
    let charpos = end;
    let bytepos = current_buffer.charpos_to_bytepos(end);
    let old_pt = current_buffer.pt;
    current_buffer.set_pt_both(charpos, bytepos);

    let compressed_buffer = unsafe {
        slice::from_raw_parts(current_buffer.byte_pos_addr(start), (end - start) as usize)
    };

    // The decompressor
    let mut decoder = create_buffer_decoder(compressed_buffer);

    let mut decompressed_bytes: isize = 0;

    loop {
        let avail_out: isize = 16 * 1024;

        let old_gap_size = current_buffer.gap_size();

        if old_gap_size < avail_out {
            unsafe { make_gap(avail_out - old_gap_size) };
        }

        let new_gap_size = avail_out;

        let gap_writer = unsafe {
            slice::from_raw_parts_mut(current_buffer.gap_start_addr(), new_gap_size as usize)
        };

        match decoder.read(gap_writer) {
            // Decompress all data finished.
            Ok(0) => {
                // Delete the compressed data.
                unsafe {
                    del_range_2(
                        start, start, // byte, char offsets the same
                        end, end, false,
                    );
                    signal_after_change(start, end - start, decompressed_bytes);

                    update_compositions(start, start, CHECK_HEAD as i32);
                };
                return true;
            }

            // Decompress one batch data successfully.
            // Continue to decompress the remaining data.
            Ok(decompressed) => {
                let decompressed = decompressed as isize;
                unsafe { insert_from_gap(decompressed, decompressed, false) };

                decompressed_bytes += decompressed;

               
    
pub fn zlib_decompress_region(start: LispObject, end: LispObject) -> bool {
    let (start, end) = validate_region_rust(start, end);

    let mut current_buffer = ThreadState::current_buffer_unchecked();

    if current_buffer.multibyte_characters_enabled() {
        error!("This function can be called only in unibyte buffers");
    };

    // Empty region, decompress failed.
    if start == end {
        return false;
    }

    unsafe {
        // Do the following before manipulating the gap.
        modify_text(start, end);

        move_gap_both(end, end);
    }

    // Insert the decompressed data at the end of the compressed data.
    let charpos = end;
    let bytepos = current_buffer.charpos_to_bytepos(end);
    let old_pt = current_buffer.pt;
    current_buffer.set_pt_both(charpos, bytepos);

    let compressed_buffer = unsafe {
        slice::from_raw_parts(current_buffer.byte_pos_addr(start), (end - start) as usize)
    };

    // The decompressor
    let mut decoder = create_buffer_decoder(compressed_buffer);

    let mut decompressed_bytes: isize = 0;

    loop {
        let avail_out: isize = 16 * 1024;

        let old_gap_size = current_buffer.gap_size();

        if old_gap_size < avail_out {
            unsafe { make_gap(avail_out - old_gap_size) };
        }

        let new_gap_size = avail_out;

        let gap_writer = unsafe {
            slice::from_raw_parts_mut(current_buffer.gap_start_addr(), new_gap_size as usize)
        };

        match decoder.read(gap_writer) {
            // Decompress all data finished.
            Ok(0) => {
                // Delete the compressed data.
                unsafe {
                    del_range_2(
                        start, start, // byte, char offsets the same
                        end, end, false,
                    );
                    signal_after_change(start, end - start, decompressed_bytes);

                    update_compositions(start, start, CHECK_HEAD as i32);
                };
                return true;
            }

            // Decompress one batch data successfully.
            // Continue to decompress the remaining data.
            Ok(decompressed) => {
                let decompressed = decompressed as isize;
                unsafe { insert_from_gap(decompressed, decompressed, false) };

                decompressed_bytes += decompressed;

                unsafe { maybe_quit() };
            }

            // Decompress failed.
            _ => {
                // Delete any uncompressed data already inserted on error, but
                // without calling the change hooks.

                let data_orig = start;
                let data_start = end;
                let data_end = end + decompressed_bytes;

                unsafe {
                    del_range_2(
                        data_start, data_start, // byte, char offsets the same
                        data_end, data_end, false,
                    );
                    update_compositions(data_start, data_start, CHECK_HEAD as i32);
                    // "Balance" the before-change-functions call, which would
                    // otherwise be left "hanging".
                    signal_after_change(data_orig, data_start - data_orig, data_start - data_orig);
                };

                // Put point where it was, or if the buffer has shrunk because the
                // compressed data is bigger than the uncompressed, at
                // point-max.
                let charpos = min(old_pt, current_buffer.zv);
                let bytepos = current_buffer.charpos_to_bytepos(charpos);
                current_buffer.set_pt_both(charpos, bytepos);

                return false;
            }
        };
    }
}