Struct ZstdReader

pub struct ZstdReader<'dict, R> { /* private fields */ }

A reader that decompresses a zstd stream from an underlying reader.

The underyling reader R should implement the following traits:

• std::io::BufRead (required for std::io::Read and std::io::BufRead impls)
• (Optional) std::io::Seek (required for std::io::Seek impl)

For async support, see crate::AsyncZstdReader.

Construction

Create a builder using either ZstdReader::builder (recommended) or ZstdReader::builder_buffered (to use a custom buffer). See ZstdReaderBuilder for build options. Call ZstdReaderBuilder::build to build the ZstdReader instance.

let reader = zstd_framed::ZstdReader::builder(compressed_file)
    // .with_seek_table(table) // Provide a seek table if available
    .build()?;

Buffering

The decompressed zstd output is always buffered internally. Since the reader must also implement std::io::BufRead, the compressed input must also be buffered.

ZstdReader::builder will wrap any reader implmenting std::io::Read with a recommended buffer size for the input stream. For more control over how the input gets buffered, you can instead use ZstdReader::builder_buffered.

Seeking

ZstdReader implements std::io::Seek as long as the underlying reader implements std::io::Seek. By default, seeking within the stream will linearly decompress until reaching the target!

Seeking can do a lot better when the underlying stream is broken up into multiple frames, such as a stream that uses the zstd seekable format. You can create such a stream using ZstdWriterBuilder::with_seek_table.

There are two situations where seeking can take advantage of a seek table:

1. When a seek table is provided up-front using ZstdReaderBuilder::with_seek_table. See crate::table::read_seek_table for reading a seek table from a reader.
2. When rewinding to a previously-decompressed frame. Frame offsets are automatically recorded during decompression.

Even if a seek table is used, seeking will still need to rewind to the start of a frame, then decompress until reaching the target offset.

Implementations

impl<R> ZstdReader<'_, BufReader<R>>

pub fn builder(reader: R) -> ZstdReaderBuilder<BufReader<R>>

where R: Read,

Create a new zstd reader that decompresses the zstd stream from the underlying reader. The provided reader will be wrapped with an appropriately-sized buffer.

pub fn builder_buffered(reader: R) -> ZstdReaderBuilder<R>

Create a new zstd reader that decompresses the zstd stream from the underlying reader. The underlying reader must implement std::io::BufRead, and its buffer will be used directly. When in doubt, use ZstdReader::builder, which uses an appropriate buffer size for decompressing a zstd stream.

Trait Implementations

impl<R> BufRead for ZstdReader<'_, R>

where R: BufRead,

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

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> Read for ZstdReader<'_, R>

where R: BufRead,

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<'_>) -> 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> Seek for ZstdReader<'_, R>

where R: BufRead + Seek,

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.