Struct memfd::MemfdOptions

pub struct MemfdOptions { /* private fields */ }

Available on Android or Linux only.

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

Implementations

impl MemfdOptions

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.

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)

fn main() {
    // Create a sealable memfd.
    let opts = memfd::MemfdOptions::default().allow_sealing(true);
    let mfd = opts.create("sized-1K").unwrap();

    // Resize to 1024B.
    mfd.as_file().set_len(1024).unwrap();

    // Add seals to prevent further resizing.
    mfd.add_seals(&[
        memfd::FileSeal::SealShrink,
        memfd::FileSeal::SealGrow
    ]).unwrap();

    // Prevent further sealing changes.
    mfd.add_seal(memfd::FileSeal::SealSeal).unwrap();

    // Write 1K of data, allowed by size seals.
    let data_1k = vec![0x00; 1024];
    let r = mfd.as_file().write_all(&data_1k);
    assert!(r.is_ok());
    mfd.as_file().seek(SeekFrom::Start(0)).unwrap();

    // Write 2K of data, now allowed by size seals.
    let data_2k = vec![0x11; 2048];
    let r = mfd.as_file().write_all(&data_2k);
    assert!(r.is_err());
    mfd.as_file().seek(SeekFrom::Start(0)).unwrap();

    // Try to resize to 2048B, not allowed by size seals.
    let r = mfd.as_file().set_len(2048);
    assert!(r.is_err());

    // Overwrite 1K of data, allowed by size seals.
    let data_1k = vec![0x22; 1024];
    let r = mfd.as_file().write_all(&data_1k);
    assert!(r.is_ok());
}

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

Whether to set the FD_CLOEXEC flag on the created Memfd.

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

Optional hugetlb support and page size for the created Memfd.

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)

fn main() {
    // Create a sealable memfd.
    let opts = memfd::MemfdOptions::default().allow_sealing(true);
    let mfd = opts.create("sized-1K").unwrap();

    // Resize to 1024B.
    mfd.as_file().set_len(1024).unwrap();

    // Add seals to prevent further resizing.
    mfd.add_seals(&[
        memfd::FileSeal::SealShrink,
        memfd::FileSeal::SealGrow
    ]).unwrap();

    // Prevent further sealing changes.
    mfd.add_seal(memfd::FileSeal::SealSeal).unwrap();

    // Write 1K of data, allowed by size seals.
    let data_1k = vec![0x00; 1024];
    let r = mfd.as_file().write_all(&data_1k);
    assert!(r.is_ok());
    mfd.as_file().seek(SeekFrom::Start(0)).unwrap();

    // Write 2K of data, now allowed by size seals.
    let data_2k = vec![0x11; 2048];
    let r = mfd.as_file().write_all(&data_2k);
    assert!(r.is_err());
    mfd.as_file().seek(SeekFrom::Start(0)).unwrap();

    // Try to resize to 2048B, not allowed by size seals.
    let r = mfd.as_file().set_len(2048);
    assert!(r.is_err());

    // Overwrite 1K of data, allowed by size seals.
    let data_1k = vec![0x22; 1024];
    let r = mfd.as_file().write_all(&data_1k);
    assert!(r.is_ok());
}

Trait Implementations

impl Clone for MemfdOptions

fn clone(&self) -> MemfdOptions

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for MemfdOptions

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for MemfdOptions

fn default() -> Self

Returns the “default value” for a type.