sized/
sized.rs

1//! A simple example showing how to crate size-sealed memfd.
2//!
3//! It creates a new memfd and seals to on a fixed 1K size.
4//!
5//! This is an example ONLY: do NOT panic/unwrap/assert
6//! in production code!
7
8extern crate memfd;
9
10use std::io::{Seek, SeekFrom, Write};
11
12fn main() {
13    // Create a sealable memfd.
14    let opts = memfd::MemfdOptions::default().allow_sealing(true);
15    let mfd = opts.create("sized-1K").unwrap();
16
17    // Resize to 1024B.
18    mfd.as_file().set_len(1024).unwrap();
19
20    // Add seals to prevent further resizing.
21    mfd.add_seals(&[
22        memfd::FileSeal::SealShrink,
23        memfd::FileSeal::SealGrow
24    ]).unwrap();
25
26    // Prevent further sealing changes.
27    mfd.add_seal(memfd::FileSeal::SealSeal).unwrap();
28
29    // Write 1K of data, allowed by size seals.
30    let data_1k = vec![0x00; 1024];
31    let r = mfd.as_file().write_all(&data_1k);
32    assert!(r.is_ok());
33    mfd.as_file().seek(SeekFrom::Start(0)).unwrap();
34
35    // Write 2K of data, now allowed by size seals.
36    let data_2k = vec![0x11; 2048];
37    let r = mfd.as_file().write_all(&data_2k);
38    assert!(r.is_err());
39    mfd.as_file().seek(SeekFrom::Start(0)).unwrap();
40
41    // Try to resize to 2048B, not allowed by size seals.
42    let r = mfd.as_file().set_len(2048);
43    assert!(r.is_err());
44
45    // Overwrite 1K of data, allowed by size seals.
46    let data_1k = vec![0x22; 1024];
47    let r = mfd.as_file().write_all(&data_1k);
48    assert!(r.is_ok());
49}
sized/sized.rs

sized/
sized.rs
