Struct BufferedSourceBuilder 

pub struct BufferedSourceBuilder { /* private fields */ }

Builder for BufferedSource. Exposes every prefetch tunable for callers whose source has a non-default latency or transfer profile; callers that just want a sensible buffer can stay on BufferedSource::new.

Defaults match BufferedSource::new: 1 MiB capacity, DEFAULT_BLOCK block size, DEFAULT_PREFETCH_TIMEOUT reader timeout, and DEFAULT_LOOKBACK_NUM / DEFAULT_LOOKBACK_DEN lookback fraction.

All tunables are clamped on build so the worker is always able to make forward progress regardless of the values handed in:

• capacity is rounded up to at least 4 * block_size bytes so each block read fits in the ring with three more behind it.
• block_size is rounded up to 4 KiB if smaller (an inner read of a few bytes per syscall would dominate the worker’s wall time).
• lookback_num / lookback_den is clamped to the range [0, 1) — a denominator of zero is treated as “no lookback” and a numerator matching the denominator is dropped to “(den - 1) / den” so the reader always has at least one byte of forward window.
• prefetch_timeout is clamped to a minimum of 1 ms so a misconfigured Duration::ZERO does not flap reads through TimedOut immediately.

Implementations

impl BufferedSourceBuilder

pub fn new() -> Self

New builder with all knobs at their defaults.

pub fn capacity(self, bytes: usize) -> Self

Set the ring capacity in bytes. Will be clamped up to at least 4 * block_size on build so the ring always holds several worker blocks.

pub fn block_size(self, bytes: usize) -> Self

Maximum bytes the worker reads from the inner source per syscall. Clamped up to 4 KiB on build. Larger values reduce per-syscall overhead at the cost of coarser-grained ring fills.

pub fn prefetch_timeout(self, dt: Duration) -> Self

Maximum time a Read will block waiting for the worker to push fresh bytes. TimedOut is surfaced on expiry. Clamped up to 1 ms on build.

pub fn lookback_fraction(self, num: u32, den: u32) -> Self

Fraction of the ring kept behind the reader as lookback so short backward seeks hit the ring. Expressed as num/den to avoid a floating-point knob (the worker uses integer division internally). 0/N disables lookback entirely. N/N is clamped to (N-1)/N so the ring keeps a forward window.

pub fn build(self, inner: Box<dyn ReadSeek>) -> Result<BufferedSource>

Build a BufferedSource from this builder and an inner source. Spawns one worker thread that takes ownership of inner.

Trait Implementations

impl Clone for BufferedSourceBuilder

fn clone(&self) -> BufferedSourceBuilder

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for BufferedSourceBuilder

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

Formats the value using the given formatter.

impl Default for BufferedSourceBuilder

fn default() -> Self

Returns the “default value” for a type.