Struct RangeReader 

pub struct RangeReader<F: RangeFetcher> { /* private fields */ }

Read + Seek over a RangeFetcher, with tail caching, read-ahead, and hard safety budgets.

See the module docs for the access-pattern and budget design.

Implementations

impl<F: RangeFetcher> RangeReader<F>

pub const fn new(fetcher: F) -> Self

Creates a reader with the default safety budgets (MAX_RANGE_REQUESTS, MAX_TRANSFER_BUDGET).

pub const fn with_limits( fetcher: F, max_requests: u32, max_transfer_bytes: u64, ) -> Self

Creates a reader with explicit safety budgets.

max_requests caps the number of range fetches; max_transfer_bytes caps the total content bytes fetched. Exceeding either fails the offending read with a std::io::Error naming the cap.

pub fn stats(&self) -> RangeStats

Transfer statistics so far (range fetches + transport probes).

pub fn total_size(&self) -> u64

Total size of the remote file in bytes.

pub const fn take_last_error(&mut self) -> Option<FetchError>

Takes the most recent typed transport error, if any.

Read flattens FetchError into std::io::Error strings; after a parse fails, callers use this to recover the typed error (e.g. to let the CLI upgrade an HTTP 403 into a gated-repo diagnosis).

impl RangeReader<HttpRangeFetcher>

pub async fn open( repo_id: &str, revision: Option<&str>, filename: &str, token: Option<&str>, ) -> Result<Self, FetchError>

Opens a range reader over filename in repo_id at revision (default main).

Performs the probe eagerly, so failures (missing file, gated repo, no Range support) surface here as typed errors rather than mid-parse io::Errors.

Must be called from within a tokio runtime; the returned reader is then handed to a blocking context (tokio::task::spawn_blocking), where its Read / Seek impls drive async requests via the captured runtime handle.

Errors

Returns FetchError::Http if the probe fails, the repository or file is inaccessible (including gated repos: returned status 401/403 errors, which the CLI upgrades into a gated-repo diagnosis), or the server does not support Range requests.

pub async fn open_with_limits( repo_id: &str, revision: Option<&str>, filename: &str, token: Option<&str>, max_requests: u32, max_transfer_bytes: u64, ) -> Result<Self, FetchError>

Opens a range reader with explicit safety budgets (see RangeReader::with_limits) instead of the MAX_RANGE_REQUESTS / MAX_TRANSFER_BUDGET defaults HttpRangeReader::open uses.

The defaults are tuned for archive-header parsing (inspect’s .safetensors / .gguf / .npz / .pth paths) — a handful of requests, well under 1 MiB. A caller with its own, larger, user-facing byte budget (hf-fm peek’s --max) needs its transport budget sized to match, or safety limits tuned for header parsing cut it off first with a misleading “pathological archive layout” error.

Same preconditions as HttpRangeReader::open (must be called from within a tokio runtime; the reader is then driven from a blocking context).

Errors

Same as HttpRangeReader::open.

pub fn probe_etag(&self) -> &str

The etag observed at probe time, before any range request.

Lets a caller key a cache entry (inspect --cache-headers) on the same etag hf-hub’s own blob layout uses, without an extra round trip beyond the probe HttpRangeReader::open already made.

Trait Implementations

impl<F: RangeFetcher> Read for RangeReader<F>

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<'_, u8>) -> 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<'_, u8>, ) -> 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.

fn read_le<T>(&mut self) -> Result<T, Error>

where T: FromEndianBytes, Self: Sized,

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

Read and return a type (e.g. an integer) in little-endian order.

fn read_be<T>(&mut self) -> Result<T, Error>

where T: FromEndianBytes, Self: Sized,

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

Read and return a type (e.g. an integer) in big-endian order.

impl<F: RangeFetcher> Seek for RangeReader<F>

fn seek(&mut self, pos: SeekFrom) -> Result<u64>

Seek to an offset, in bytes, in a stream.

fn rewind(&mut self) -> Result<(), Error>

Rewind to the beginning of a stream.

fn stream_len(&mut self) -> Result<u64, Error>

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

Returns the length of this stream (in bytes).

fn stream_position(&mut self) -> Result<u64, Error>

Returns the current seek position from the start of the stream.

fn seek_relative(&mut self, offset: i64) -> Result<(), Error>

Seeks relative to the current position.