Struct MmapRegion 

pub struct MmapRegion { /* private fields */ }

File-backed memory-mapped region for cross-process shared memory.

shm[impl shm.file.mmap-posix]

Implementations

impl MmapRegion

pub fn create(path: &Path, size: usize, cleanup: FileCleanup) -> Result<Self>

Create a new file-backed region.

This creates the file, truncates it to the given size, and maps it into memory with MAP_SHARED. The file is created with permissions 0600.

shm[impl shm.file.create] shm[impl shm.file.permissions]

pub fn attach(path: &Path) -> Result<Self>

Attach to an existing file-backed region.

This opens the file and maps it into memory with MAP_SHARED. The file size determines the mapping size.

shm[impl shm.file.attach]

pub fn region(&self) -> Region

Get a Region view of this mmap.

pub fn len(&self) -> usize

Get the size of the region in bytes.

pub fn is_empty(&self) -> bool

Returns true if the region is empty (zero bytes).

pub fn path(&self) -> &Path

Get the path to the backing file.

pub fn take_ownership(&mut self)

Take ownership of the file for cleanup purposes.

After calling this, the file will be deleted when this region is dropped.

pub fn release_ownership(&mut self)

Release ownership of the file.

After calling this, the file will NOT be deleted when this region is dropped.

pub fn resize(&mut self, new_size: usize) -> Result<()>

Resize the region by growing the backing file and remapping.

This is typically a host-only operation. The base pointer may change, so callers must update any cached Region references after calling this.

Errors

Returns an error if the new size is smaller than current size (shrinking is not supported), or if the underlying file/mmap operations fail.

shm[impl shm.varslot.extents]

pub fn check_and_remap(&mut self) -> Result<bool>

Check if the backing file has grown and remap if needed.

This is useful for guests to detect when the host has grown the segment. Returns true if the region was remapped, false if no change.

Errors

Returns an error if file metadata cannot be read or remapping fails.

Trait Implementations

impl Drop for MmapRegion

fn drop(&mut self)

Executes the destructor for this type.

impl Send for MmapRegion

impl Sync for MmapRegion