Struct Memfd

Source

pub struct Memfd { /* private fields */ }

Available on Android or Linux only.

Expand description

An anonymous volatile file, with sealing capabilities.

Implementations§

Source §

impl Memfd

Source

pub fn try_from_fd<F>(fd: F) -> Result<Self, F>
where F: AsRawFd + IntoRawFd,

Try to convert an object that owns a file descriptor into a Memfd.

This function consumes the ownership of the specified object. If the underlying file-descriptor is compatible with memfd/sealing, a Memfd object is returned. Otherwise the supplied object is returned as error.

Source

pub fn try_from_file(file: File) -> Result<Self, File>

Try to convert a File object into a Memfd.

This function consumes the ownership of the specified File. If the underlying file-descriptor is compatible with memfd/sealing, a Memfd object is returned. Otherwise the supplied File is returned for further usage.

Source

pub const fn as_file(&self) -> &File

Return a reference to the backing File.

Examples found in repository ?

examples/sized.rs (line 18)

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 fn into_file(self) -> File

Convert Memfd to the backing File.

Source

pub fn seals(&self) -> Result<SealsHashSet, Error>

Obtain the current set of seals for the Memfd.

Source

pub fn add_seal(&self, seal: FileSeal) -> Result<(), Error>

Add a seal to the existing set of seals.

Examples found in repository ?

examples/sized.rs (line 27)

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 fn add_seals<'a>( &self, seals: impl IntoIterator<Item = &'a FileSeal>, ) -> Result<(), Error>

Add some seals to the existing set of seals.

Examples found in repository ?

examples/sized.rs (lines 21-24)

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}