Struct ZranGenerator 

pub struct ZranGenerator<R> { /* private fields */ }

Struct to generate random access information for OCIv1 image tarballs.

ZranGenerator generates decompression context information to support random access to the tarball later. It only tracks information related to Tar file content, and ignores all other tar headers and zlib headers when possible. The work flow is:

1. create a ZranGenerator object zran.
2. create a tar::Archive object from zran.
3. walk all entries in the tarball, for each tar regular file: 3.1) get file size and split it into chunks, for each file data chunk 3.2) call zran.begin_data_chunk() 3.3) read file content from the tar Entry object 3.4) call zran.end_data_chunk() to get chunk decompression information
4. call zran.get_compression_info_array() to get all decompression context information for random access later

Implementations

impl<R: Read> ZranGenerator<R>

pub fn new(reader: ZranReader<R>) -> Self

Create a new instance of ZranGenerator from a reader.

pub fn begin_read(&mut self, chunk_size: u64) -> Result<u32>

Begin a transaction to read data from the zlib stream.

Arguments

• chunk_size: size of data to be read from the zlib stream.

pub fn end_read(&mut self) -> Result<ZranChunkInfo>

Mark end of a data read operation and returns information to decode data from the random access slice.

pub fn get_compression_ctx_array(&self) -> &[ZranContext]

Get an immutable reference to the random access context information array.

pub fn set_min_compressed_size(&mut self, sz: u64)

Set minimal compressed size to emit an random access slice.

Please ensure “min_compressed_size * 2 <= max_compressed_size”.

pub fn set_max_compressed_size(&mut self, sz: u64)

Set maximum compressed size to emit an random access slice.

Please ensure “min_compressed_size * 2 <= max_compressed_size”.

pub fn set_max_uncompressed_size(&mut self, sz: u64)

Set maximum uncompressed size to emit an random access slice.

Please ensure “min_compressed_size * 2 < max_compressed_size”.

Trait Implementations

impl<R: Read> Read for ZranGenerator<R>

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” 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.