mmarinus

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

For example:

use mmarinus::{Map, perms};
use std::io::Read;

let mut hosts = std::fs::File::open("/etc/hosts").unwrap();

let mut chunk = [0u8; 32];
hosts.read_exact(&mut chunk).unwrap();

let map = Map::bytes(32)
    .near(128 * 1024 * 1024)
    .from(&mut hosts, 0)
    .with(perms::Read)
    .unwrap();

assert_eq!(&*map, &chunk);

You can also remap an existing mapping:

use mmarinus::{Map, perms};
use std::io::Read;

let mut hosts = std::fs::File::open("/etc/hosts").unwrap();

let mut chunk = [0u8; 32];
hosts.read_exact(&mut chunk).unwrap();

let mut map = Map::bytes(32)
    .anywhere()
    .from(&mut hosts, 0)
    .with(perms::Read)
    .unwrap();

assert_eq!(&*map, &chunk);

let mut map = map.remap()
    .from(&mut hosts, 0)
    .with(perms::ReadWrite)
    .unwrap();

assert_eq!(&*map, &chunk);

for i in map.iter_mut() {
    *i = 255;
}
assert_eq!(&*map, &[255; 32]);

Alternatively, you can just change the permissions:

use mmarinus::{Map, perms};
use std::io::Read;

let mut hosts = std::fs::File::open("/etc/hosts").unwrap();

let mut chunk = [0u8; 32];
hosts.read_exact(&mut chunk).unwrap();

let map = Map::bytes(32)
    .near(128 * 1024 * 1024)
    .from(&mut hosts, 0)
    .with(perms::Read)
    .unwrap();

assert_eq!(&*map, &chunk);

let mut map = map.reprotect(perms::ReadWrite).unwrap();
assert_eq!(&*map, &chunk);

for i in map.iter_mut() {
    *i = 255;
}
assert_eq!(&*map, &[255; 32]);

Mapping a whole file into memory is easy:

use mmarinus::{Map, Private, perms};

let map = Map::load("/etc/hosts", Private, perms::Read).unwrap();

License: Apache-2.0