Struct MmapDiskWriter 

pub struct MmapDiskWriter { /* private fields */ }

A disk writer that uses memory-mapped I/O for high-performance reads/writes.

Falls back to PositionedDiskWriter (positioned pwrite/seek_write) when mmap cannot be created (e.g., zero-length file) or after truncate is called (remapping after resize is not supported in v1).

Example

use aria2_core::filesystem::mmap_disk_writer::MmapDiskWriter;
use aria2_core::filesystem::disk_writer::SeekableDiskWriter;

let mut writer = MmapDiskWriter::new(std::path::Path::new("output.bin"), Some(4096));
writer.open().await?;
writer.write_at(0, b"hello mmap").await?;
writer.flush().await?;

Implementations

impl MmapDiskWriter

pub fn new(path: &Path, total_size: Option<u64>) -> Self

Create a new MmapDiskWriter for the given path.

If total_size is provided and the file is newly created (size 0), the file is pre-allocated to total_size bytes on first open. This is required for mmap since a zero-length file cannot be mapped.

Trait Implementations

impl SeekableDiskWriter for MmapDiskWriter

fn write_bytes_at<'life0, 'async_trait>( &'life0 mut self, offset: u64, data: Bytes, ) -> Pin<Box<dyn Future<Output = Result<()>> + Send + 'async_trait>>

where Self: 'async_trait, 'life0: 'async_trait,

Write Bytes to the mmap region.

For the mmap variant, a memory copy is unavoidable — Bytes is an Arc-backed buffer that cannot be “injected” into the mmap region. For the fallback variant, this is zero-copy (pwrite takes &data).

fn close<'life0, 'async_trait>( &'life0 mut self, ) -> Pin<Box<dyn Future<Output = Result<()>> + Send + 'async_trait>>

where Self: 'async_trait, 'life0: 'async_trait,

Close the writer, releasing the file handle and memory mapping.

After close, the writer can be reopened with open().

fn open<'life0, 'async_trait>( &'life0 mut self, ) -> Pin<Box<dyn Future<Output = Result<()>> + Send + 'async_trait>>

where Self: 'async_trait, 'life0: 'async_trait,

fn write_at<'life0, 'life1, 'async_trait>( &'life0 mut self, offset: u64, data: &'life1 [u8], ) -> Pin<Box<dyn Future<Output = Result<()>> + Send + 'async_trait>>

where Self: 'async_trait, 'life0: 'async_trait, 'life1: 'async_trait,

fn read_at<'life0, 'life1, 'async_trait>( &'life0 mut self, offset: u64, buf: &'life1 mut [u8], ) -> Pin<Box<dyn Future<Output = Result<usize>> + Send + 'async_trait>>

where Self: 'async_trait, 'life0: 'async_trait, 'life1: 'async_trait,

fn truncate<'life0, 'async_trait>( &'life0 mut self, length: u64, ) -> Pin<Box<dyn Future<Output = Result<()>> + Send + 'async_trait>>

where Self: 'async_trait, 'life0: 'async_trait,

fn flush<'life0, 'async_trait>( &'life0 mut self, ) -> Pin<Box<dyn Future<Output = Result<()>> + Send + 'async_trait>>

where Self: 'async_trait, 'life0: 'async_trait,

fn len<'life0, 'async_trait>( &'life0 self, ) -> Pin<Box<dyn Future<Output = Result<u64>> + Send + 'async_trait>>

where Self: 'async_trait, 'life0: 'async_trait,

fn path(&self) -> &Path