Struct BufReader

pub struct BufReader<R, P = StdPolicy> { /* private fields */ }

A drop-in replacement for std::io::BufReader with more functionality.

Original method names/signatures and implemented traits are left untouched, making replacement as simple as swapping the import of the type.

By default this type implements the behavior of its std counterpart: it only reads into the buffer when it is empty.

To change this type’s behavior, change the policy with .set_policy() using a type from the policy module or your own implementation of ReaderPolicy.

Policies that perform alternating reads and consumes without completely emptying the buffer may benefit from using a ringbuffer via the new_ringbuf() and with_capacity_ringbuf() constructors. Ringbuffers are only available on supported platforms with the slice-deque feature and have some other caveats; see the crate root docs for more details.

Implementations

impl<R> BufReader<R>

pub fn new(inner: R) -> BufReader<R>

Create a new BufReader wrapping inner, utilizing a buffer of default capacity and the default ReaderPolicy.

pub fn with_capacity(cap: usize, inner: R) -> BufReader<R>

Create a new BufReader wrapping inner, utilizing a buffer with a capacity of at least cap bytes and the default ReaderPolicy.

The actual capacity of the buffer may vary based on implementation details of the global allocator.

pub fn with_buffer(buf: Buffer, inner: R) -> BufReader<R>

Wrap inner with an existing Buffer instance and the default ReaderPolicy.

Note

Does not clear the buffer first! If there is data already in the buffer then it will be returned in read() and fill_buf() ahead of any data from inner.

impl<R, P> BufReader<R, P>

pub fn set_policy<P_>(self, policy: P_) -> BufReader<R, P_>

where P_: ReaderPolicy,

Apply a new ReaderPolicy to this BufReader, returning the transformed type.

pub fn policy_mut(&mut self) -> &mut P

Mutate the current ReaderPolicy in-place.

If you want to change the type, use .set_policy().

pub fn policy(&self) -> &P

Inspect the current ReaderPolicy.

pub fn make_room(&mut self)

Move data to the start of the buffer, making room at the end for more reading.

This is a no-op with the *_ringbuf() constructors (requires slice-deque feature).

pub fn reserve(&mut self, additional: usize)

Ensure room in the buffer for at least additional bytes. May not be quite exact due to implementation details of the buffer’s allocator.

pub fn buffer(&self) -> &[u8]

Get the section of the buffer containing valid data; may be empty.

Call .consume() to remove bytes from the beginning of this section.

pub fn buf_len(&self) -> usize

Get the current number of bytes available in the buffer.

pub fn capacity(&self) -> usize

Get the total buffer capacity.

pub fn get_ref(&self) -> &R

Get an immutable reference to the underlying reader.

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

Get a mutable reference to the underlying reader.

Note

Reading directly from the underlying reader is not recommended, as some data has likely already been moved into the buffer.

pub fn into_inner(self) -> R

Consume self and return the inner reader only.

pub fn into_inner_with_buffer(self) -> (R, Buffer)

Consume self and return both the underlying reader and the buffer.

See also: BufReader::unbuffer()

pub fn unbuffer(self) -> Unbuffer<R>

Consume self and return an adapter which implements Read and will empty the buffer before reading directly from the underlying reader.

impl<R, P> BufReader<R, P>

where R: Read,

pub fn read_into_buf(&mut self) -> Result<usize, Error>

Unconditionally perform a read into the buffer.

Does not invoke ReaderPolicy methods.

If the read was successful, returns the number of bytes read.

pub fn boxed<'a>(self) -> BufReader<Box<dyn Read + 'a>, P>

where R: 'a,

Box the inner reader without losing data.

Trait Implementations

impl<R, P> BufRead for BufReader<R, P>

where R: Read, P: ReaderPolicy,

fn fill_buf(&mut self) -> Result<&[u8], Error>

Returns the contents of the internal buffer, filling it with more data from the inner reader if it is empty.

fn consume(&mut self, amt: usize)

Tells this buffer that amt bytes have been consumed from the buffer, so they should no longer be returned in calls to read.

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

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

Checks if the underlying Read has any data left to be read.

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

Reads all bytes into buf until the delimiter byte or EOF is reached.

fn skip_until(&mut self, byte: u8) -> Result<usize, Error>

Skips all bytes until the delimiter byte or EOF is reached.

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

Reads all bytes until a newline (the 0xA byte) is reached, and append them to the provided String buffer.

fn split(self, byte: u8) -> Split<Self>

where Self: Sized,

Returns an iterator over the contents of this reader split on the byte byte.

fn lines(self) -> Lines<Self>

where Self: Sized,

Returns an iterator over the lines of this reader.

impl<R, P> Debug for BufReader<R, P>

where R: Debug, P: Debug,

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

Formats the value using the given formatter.

impl<R, P> Read for BufReader<R, P>

where R: Read, P: ReaderPolicy,

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

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” adaptor 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.

impl<R, P> Seek for BufReader<R, P>

where R: Seek, P: ReaderPolicy,

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

Seek to an ofPet, in bytes, in the underlying reader.

The position used for seeking with SeekFrom::Current(_) is the position the underlying reader would be at if the BufReader had no internal buffer.

Seeking always discards the internal buffer, even if the seek position would otherwise fall within it. This guarantees that calling .unwrap() immediately after a seek yields the underlying reader at the same position.

See std::io::Seek for more details.

Note: In the edge case where you’re seeking with SeekFrom::Current(n) where n minus the internal buffer length underflows an i64, two seeks will be performed instead of one. If the second seek returns Err, the underlying reader will be left at the same position it would have if you seeked to SeekFrom::Current(0).

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.