Struct memmap::Mmap

pub struct Mmap { /* fields omitted */ }

An immutable memory mapped buffer.

A Mmap may be backed by a file, or it can be anonymous map, backed by volatile memory.

Use MmapOptions to configure and create a file-backed memory map. To create an immutable anonymous memory map, first create a mutable anonymous memory map using MmapOptions, and then make it immutable with MmapMut::make_read_only.

Example

use memmap::MmapOptions;
use std::io::Write;
use std::fs::File;

let file = File::open("README.md")?;
let mmap = unsafe { MmapOptions::new().map(&file)? };
assert_eq!(b"# memmap", &mmap[0..8]);

See MmapMut for the mutable version.

Implementations

impl Mmap

pub unsafe fn map(file: &File) -> Result<Mmap>

Creates a read-only memory map backed by a file.

This is equivalent to calling MmapOptions::new().map(file).

Errors

This method returns an error when the underlying system call fails, which can happen for a variety of reasons, such as when the file is not open with read permissions.

Example

use std::fs::File;
use std::io::Read;

use memmap::Mmap;

let mut file = File::open("README.md")?;

let mut contents = Vec::new();
file.read_to_end(&mut contents)?;

let mmap = unsafe { Mmap::map(&file)?  };

assert_eq!(&contents[..], &mmap[..]);

pub fn make_mut(self) -> Result<MmapMut>

Transition the memory map to be writable.

If the memory map is file-backed, the file must have been opened with write permissions.

Errors

This method returns an error when the underlying system call fails, which can happen for a variety of reasons, such as when the file is not open with writable permissions.

Example

use memmap::Mmap;
use std::ops::DerefMut;
use std::io::Write;

let file = /* file opened with write permissions */
let mmap = unsafe { Mmap::map(&file)? };
// ... use the read-only memory map ...
let mut mut_mmap = mmap.make_mut()?;
mut_mmap.deref_mut().write_all(b"hello, world!")?;

Trait Implementations

impl AsRef<[u8]> for Mmap

fn as_ref(&self) -> &[u8]

Performs the conversion.

impl Debug for Mmap

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

Formats the value using the given formatter.

impl Deref for Mmap

type Target = [u8]

The resulting type after dereferencing.

fn deref(&self) -> &[u8]

Dereferences the value.