Struct Reader 

pub struct Reader<R, D> {
    reader: R,
    operation: D,
    state: State,
    single_frame: bool,
    finished_frame: bool,
    started: bool,
}

Implements the Read API around an Operation.

This can be used to wrap a raw in-memory operation in a read-focused API.

It can wrap either a compression or decompression operation, and pulls input data from a wrapped Read.

Fields

reader: R

operation: D

state: State

single_frame: bool

finished_frame: bool

started: bool

Implementations

impl<R, D> Reader<R, D>

pub fn new(reader: R, operation: D) -> Self

Creates a new Reader.

reader will be used to pull input data for the given operation.

pub fn set_single_frame(&mut self)

Sets self to stop after the first decoded frame.

pub fn operation_mut(&mut self) -> &mut D

Returns a mutable reference to the underlying operation.

pub fn reader_mut(&mut self) -> &mut R

Returns a mutable reference to the underlying reader.

pub fn reader(&self) -> &R

Returns a reference to the underlying reader.

pub fn into_inner(self) -> R

Returns the inner reader.

pub fn flush(&mut self, output: &mut [u8]) -> Result<usize>

where D: Operation,

Flush any internal buffer.

For encoders, this ensures all input consumed so far is compressed.

impl<R, D> Reader<R, D>

where R: BufRead, D: Operation,

pub fn finish_frame(&mut self) -> Result<()>

Consume the rest of the current frame from the underlying reader.

Once all the decoded data has been read, zstd may still not have consumed the tail of the frame: it can produce the last of the output before reading the frame epilogue. The underlying reader is then left pointing somewhere inside the frame rather than just after it.

This feeds zstd the input it still needs, with no room for output, so the reader ends up positioned exactly at the end of the frame.

It stops there: it will not start decoding whatever follows, so a stream of concatenated frames keeps its remaining frames, and trailing non-zstd data is left untouched.

This is a no-op if the current frame is already complete, or if no frame has been started yet, so it will not read from the underlying reader in those cases.

Trait Implementations

impl<R, D> Read for Reader<R, D>

where R: BufRead, D: Operation,

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

Reads everything the operation produces into buf.

The default implementation has an awkward ending: when the output happens to fill the vector exactly, it doubles the capacity and reallocates - copying everything decoded so far - then reads zero bytes and truncates back. Probing with a small stack buffer first establishes there is nothing left without paying for that. Whether the saving shows up depends on the allocator: one that can grow a large block in place makes it cheap, one that has to copy does not.

This should be deleted once Read::read_buf is stable. std can then fill spare capacity without initializing it first, which removes both the reallocation and the zeroing this does by hand, and its version will be the better one.

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_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.