mmarinus

The mmarinus crate wraps the underlying system mmap() call in safe semantics.

For example:

use std::num::NonZeroUsize;
use mmarinus::{Kind, Builder, perms};

let mut zero = std::fs::File::open("/dev/zero").unwrap();

let map = Builder::map(4096)
    .near(128 * 1024 * 1024)
    .from(&mut zero, 0)
    .known::<perms::Read>(Kind::Private)
    .unwrap();

assert_eq!(&*map, &[0; 4096]);

You can also remap an existing mapping:

use std::num::NonZeroUsize;
use mmarinus::{Kind, Builder, perms};

let mut zero = std::fs::File::open("/dev/zero").unwrap();

let mut map = Builder::map(4096)
    .anywhere()
    .from(&mut zero, 0)
    .known::<perms::Read>(Kind::Private)
    .unwrap();

assert_eq!(&*map, &[0; 4096]);

let mut map = map.remap()
    .from(&mut zero, 0)
    .known::<perms::ReadWrite>(Kind::Private)
    .unwrap();

assert_eq!(&*map, &[0; 4096]);
for i in map.iter_mut() {
    *i = 255;
}
assert_eq!(&*map, &[255; 4096]);

Alternatively, you can just change the permissions:

use std::num::NonZeroUsize;
use mmarinus::{Kind, Builder, perms};

let mut zero = std::fs::File::open("/dev/zero").unwrap();

let mut map = Builder::map(4096)
    .at(128 * 1024 * 1024)
    .from(&mut zero, 0)
    .known::<perms::Read>(Kind::Private)
    .unwrap();

assert_eq!(&*map, &[0; 4096]);

let mut map = map.reprotect::<perms::ReadWrite>().unwrap();

assert_eq!(&*map, &[0; 4096]);
for i in map.iter_mut() {
    *i = 255;
}
assert_eq!(&*map, &[255; 4096]);

Mapping a whole file into memory is easy:

use std::num::NonZeroUsize;
use mmarinus::{Kind, Builder, perms};

let map = Kind::Private.load::<perms::Read, _>("/etc/os-release").unwrap();

License: Apache-2.0