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, via Read methods, if empty.

fn consume(&mut self, amt: usize)

Marks the given amount of additional bytes from the internal buffer as having been read. Subsequent calls to read only return bytes that have not been marked as read.

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

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

Checks if there is 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.