Struct MemfdOptions

Source

pub struct MemfdOptions { /* private fields */ }

Available on Android or Linux only.

Expand description

A Memfd builder, providing advanced options and flags for specifying its behavior.

Implementations§

Source §

impl MemfdOptions

Source

pub const fn new() -> Self

Default set of options for Memfd creation.

The default options are:

FileSeal::SealSeal (i.e. no further sealing);
close-on-exec is enabled;
hugetlb is disabled.

Source

pub const fn allow_sealing(self, value: bool) -> Self

Whether to allow adding seals to the created Memfd.

Examples found in repository ?

examples/sized.rs (line 14)

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}

Source

pub const fn close_on_exec(self, value: bool) -> Self

Whether to set the FD_CLOEXEC flag on the created Memfd.

Source

pub const fn hugetlb(self, size: Option<HugetlbSize>) -> Self

Optional hugetlb support and page size for the created Memfd.

Source

pub fn create<T: AsRef<str>>(&self, name: T) -> Result<Memfd, Error>

Create a Memfd according to configuration.

Examples found in repository ?

examples/sized.rs (line 15)

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}