Struct bao::decode::SliceDecoder

pub struct SliceDecoder<T: Read> { /* private fields */ }

An incremental slice decoder. This reads and verifies the output of the SliceExtractor.

Note that there is no such thing as an “outboard slice”. All slices include the content bytes and tree nodes intermixed, as in the combined encoding mode.

Example

use std::io::prelude::*;

// Start by encoding some input.
let input = vec![0; 1_000_000];
let (encoded, hash) = bao::encode::encode(&input);

// Slice the encoding. These parameters are multiples of the chunk size, which avoids
// unnecessary overhead.
let slice_start = 65536;
let slice_len = 8192;
let encoded_cursor = std::io::Cursor::new(&encoded);
let mut extractor = bao::encode::SliceExtractor::new(encoded_cursor, slice_start, slice_len);
let mut slice = Vec::new();
extractor.read_to_end(&mut slice)?;

// Decode the slice. The result should be the same as the part of the input that the slice
// represents. Note that we're using the same hash that encoding produced, which is
// independent of the slice parameters. That's the whole point; if we just wanted to re-encode
// a portion of the input and wind up with a different hash, we wouldn't need slicing.
let mut decoded = Vec::new();
let mut decoder = bao::decode::SliceDecoder::new(&*slice, &hash, slice_start, slice_len);
decoder.read_to_end(&mut decoded)?;
assert_eq!(&input[slice_start as usize..][..slice_len as usize], &*decoded);

// Like regular decoding, slice decoding will fail if the hash doesn't match.
let mut bad_slice = slice.clone();
let last_index = bad_slice.len() - 1;
bad_slice[last_index] ^= 1;
let mut decoder = bao::decode::SliceDecoder::new(&*bad_slice, &hash, slice_start, slice_len);
let err = decoder.read_to_end(&mut Vec::new()).unwrap_err();
assert_eq!(std::io::ErrorKind::InvalidData, err.kind());

Implementations

impl<T: Read> SliceDecoder<T>

pub fn new(inner: T, hash: &Hash, slice_start: u64, slice_len: u64) -> Self

pub fn into_inner(self) -> T

Return the underlying reader.

Trait Implementations

impl<T: Read> Read for SliceDecoder<T>

fn read(&mut self, output: &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, Global>) -> Result<usize, Error>

Read all bytes until EOF in this source, placing them into buf.

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

Read all bytes until EOF in this source, appending them to buf.

fn read_exact(&mut self, buf: &mut [u8]) -> Result<(), Error>

Read the exact number of bytes required to fill buf.

fn read_buf(&mut self, buf: &mut ReadBuf<'_>) -> 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, buf: &mut ReadBuf<'_>) -> Result<(), Error>

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

Read the exact number of bytes required to fill buf.

fn by_ref(&mut self) -> &mut Self

Creates a “by reference” adaptor for this instance of Read.

fn bytes(self) -> Bytes<Self>

Transforms this Read instance to an Iterator over its bytes.

fn chain<R>(self, next: R) -> Chain<Self, R> where
    R: Read, 

Creates an adapter which will chain this stream with another.

fn take(self, limit: u64) -> Take<Self>

Creates an adapter which will read at most limit bytes from it.