Struct Lengths 

pub struct Lengths { /* private fields */ }

Piece and chunk arithmetic for BitTorrent downloads.

Manages the mapping between:

• Pieces: fixed-size blocks verified by SHA1 (except possibly the last piece)
• Chunks: sub-piece blocks requested from peers (typically 16 KiB)
• Files: the actual files on disk that pieces map across

Implementations

impl Lengths

pub fn new(total_length: u64, piece_length: u64, chunk_size: u32) -> Self

Create a new Lengths calculator.

Panics

Panics if piece_length or chunk_size is 0.

pub fn total_length(&self) -> u64

Total size of all content.

pub fn piece_length(&self) -> u64

Standard piece length.

pub fn chunk_size(&self) -> u32

Chunk/block size.

pub fn num_pieces(&self) -> u32

Total number of pieces.

pub fn piece_size(&self, piece_index: u32) -> u32

Actual length of a specific piece (last piece may be shorter).

pub fn chunks_in_piece(&self, piece_index: u32) -> u32

Number of chunks in a specific piece.

pub fn chunk_info( &self, piece_index: u32, chunk_index: u32, ) -> Option<(u32, u32)>

Offset and length of a specific chunk within a piece.

Returns (offset_within_piece, chunk_length).

pub fn piece_offset(&self, piece_index: u32) -> u64

Absolute byte offset for the start of a piece.

pub fn piece_index_for_byte(&self, byte_offset: u64) -> Option<u32>

Map an absolute byte offset to a piece index.

Returns None when byte_offset >= total_length.

Prefer this over the ad-hoc (byte / piece_length) as u32 form: M132’s in-flight underflow is the cautionary precedent for narrowing casts on hot paths. Routing all byte→piece conversions through one bounded function keeps that bug class in one place.

pub fn byte_to_piece_with_offset(&self, byte_offset: u64) -> Option<(u32, u32)>

Map an absolute byte offset to (piece_index, offset_within_piece).

Sibling of Self::piece_index_for_byte for callers that also need the offset within the piece (e.g. disk reads at a sub-piece position). Returns None when byte_offset >= total_length.

pub fn file_pieces( &self, file_offset: u64, file_length: u64, ) -> Option<(u32, u32)>

Given file boundaries, determine which pieces a file spans. Returns (first_piece, last_piece) inclusive.

Trait Implementations

impl Clone for Lengths

fn clone(&self) -> Lengths

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Lengths

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

Formats the value using the given formatter.

impl PartialEq for Lengths

fn eq(&self, other: &Lengths) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Eq for Lengths

impl StructuralPartialEq for Lengths