compress data using win32 api in rust

To compress data using the Win32 API in Rust, we can use the zlib library. This library provides functions for compressing and decompressing data using the zlib algorithm, which is commonly used for file compression.

To get started, we need to include the winapi and libc crates in our project:

main.rs
extern crate winapi;
extern crate libc;
40 chars
3 lines

We also need to link against the zlib1 library by adding the following lines to our Cargo.toml file:

main.rs
[dependencies]
libc = "0.2"
winapi = { version = "0.3", features = ["winuser"] }
81 chars
4 lines

With the dependencies set up, we can start writing code to compress data. Here's an example function that compresses a byte buffer using the zlib library:

main.rs
use winapi::um::{winnt, errhandlingapi};
use winapi::shared::{minwindef, windef};
use libc::c_void;

fn compress_data(input: &[u8]) -> Option<Vec<u8>> {
    // Set up input and output buffers
    let input_size = input.len();
    let mut output_size = input_size + input_size / 10 + 12;
    let mut output_buffer: Vec<u8> = vec![0; output_size];
    let mut input_buffer = input.clone();
    
    // Compress data using zlib
    let result = unsafe {
        winapi::um::winsock2::compress(
            output_buffer.as_mut_ptr() as *mut c_void,
            &mut output_size as *mut _ as *mut _,
            input_buffer.as_mut_ptr() as *mut c_void,
            input_size as minwindef::u_long,
            zlib_const::Z_BEST_COMPRESSION,
        )
    };
    
    if result == winnt::Z_OK {
        output_buffer.resize(output_size, 0);
        Some(output_buffer)
    } else {
        None
    }
}
900 chars
30 lines

We start by setting up input and output buffers. The output buffer is initialized with a size that is 10% larger than the input size plus 12 bytes, which is a common heuristic for estimating the size of the compressed output. We then call the compress function from the winsock2 module, which compresses the data in the input buffer and stores the compressed data in the output buffer.

The compress function returns Z_OK if the compression was successful. If so, we resize the output buffer to the actual compressed size and return it as a Vec<u8>. Otherwise, we return None.

Note that this is just a simple example of how to compress data using the Win32 API in Rust. We would likely want to handle errors more gracefully in a real-world scenario, and we might also want to use other compression algorithms or libraries depending on our specific use case.