Struct PrefetchReader 

pub struct PrefetchReader { /* private fields */ }

A Read adapter that performs asynchronous userspace prefetch on a dedicated background thread.

See the module docs for the rationale and lifecycle model.

Example

use std::io::{Cursor, Read};
use fgumi_lib::prefetch_reader::PrefetchReader;

let data: Vec<u8> = (0..1024).map(|i| (i % 256) as u8).collect();
let mut reader = PrefetchReader::new(Cursor::new(data.clone()));
let mut out = Vec::new();
reader.read_to_end(&mut out).unwrap();
assert_eq!(out, data);

Implementations

impl PrefetchReader

pub fn new<R: Read + Send + 'static>(inner: R) -> Self

Construct a PrefetchReader from an arbitrary reader with default chunk size and prefetch depth.

No posix_fadvise(WILLNEED) hints are issued because the inner reader may not be backed by a file descriptor. Use from_file when wrapping a File to get kernel page-cache warming for free.

pub fn with_config<R: Read + Send + 'static>( inner: R, chunk_size: usize, prefetch_depth: usize, ) -> Self

Construct a PrefetchReader from an arbitrary reader with explicit chunk_size and prefetch_depth.

Steady-state memory usage is bounded by chunk_size * prefetch_depth (plus one chunk being filled by the producer and one being consumed).

Panics

Panics if chunk_size == 0 or prefetch_depth == 0.

pub fn from_file(file: File) -> Self

Construct a PrefetchReader from a File with default chunk size and prefetch depth.

On Linux the producer thread will call posix_fadvise(POSIX_FADV_WILLNEED) after each chunk fill to proactively page in the next [WILLNEED_LOOKAHEAD] bytes, making the reader independent of the kernel’s default read-ahead window (read_ahead_kb). On non-Linux platforms this behaves identically to new.

The file should be positioned at offset 0 when passed in — the WILLNEED hints assume reading starts from the beginning of the file.

pub fn from_file_with_config( file: File, chunk_size: usize, prefetch_depth: usize, ) -> Self

Construct a PrefetchReader from a File with explicit chunk_size and prefetch_depth, plus kernel WILLNEED hints on Linux.

Panics

Panics if chunk_size == 0 or prefetch_depth == 0.

pub fn bytes_consumed(&self) -> u64

Total bytes served to callers of Read::read so far.

pub fn consumer_stalls(&self) -> u64

Number of times a read call had to block waiting for the producer to deliver the next chunk. Useful as a prototype-phase signal for whether DEFAULT_PREFETCH_DEPTH is large enough.

Trait Implementations

impl Debug for PrefetchReader

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

Formats the value using the given formatter.

impl Drop for PrefetchReader

fn drop(&mut self)

Executes the destructor for this type.

impl Read for PrefetchReader

fn read(&mut self, buf: &mut [u8]) -> Result<usize>

Pull some bytes from this source into the specified buffer, returning how many bytes were read.

fn read_vectored(&mut self, bufs: &mut [IoSliceMut<'_>]) -> Result<usize, Error>

Like read, except that it reads into a slice of buffers.

fn is_read_vectored(&self) -> bool

🔬This is a nightly-only experimental API. (can_vector)

Determines if this Reader has an efficient read_vectored implementation.

fn read_to_end(&mut self, buf: &mut Vec<u8>) -> Result<usize, Error>

Reads all bytes until EOF in this source, placing them into buf.

fn read_to_string(&mut self, buf: &mut String) -> Result<usize, Error>

Reads all bytes until EOF in this source, appending them to buf.

fn read_exact(&mut self, buf: &mut [u8]) -> Result<(), Error>

Reads the exact number of bytes required to fill buf.

fn read_buf(&mut self, buf: BorrowedCursor<'_>) -> Result<(), Error>

🔬This is a nightly-only experimental API. (read_buf)

Pull some bytes from this source into the specified buffer.

fn read_buf_exact(&mut self, cursor: BorrowedCursor<'_>) -> Result<(), Error>

🔬This is a nightly-only experimental API. (read_buf)

Reads the exact number of bytes required to fill cursor.

fn by_ref(&mut self) -> &mut Self

where Self: Sized,

Creates a “by reference” adapter for this instance of Read.

fn bytes(self) -> Bytes<Self>

where Self: Sized,

Transforms this Read instance to an Iterator over its bytes.

fn chain<R>(self, next: R) -> Chain<Self, R>

where R: Read, Self: Sized,

Creates an adapter which will chain this stream with another.

fn take(self, limit: u64) -> Take<Self>

where Self: Sized,

Creates an adapter which will read at most limit bytes from it.

fn read_array<const N: usize>(&mut self) -> Result<[u8; N], Error>

where Self: Sized,

🔬This is a nightly-only experimental API. (read_array)

Read and return a fixed array of bytes from this source.