Struct bao::decode::SliceReader

pub struct SliceReader<T: Read> { /* fields omitted */ }

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

Note that there is no such thing as an "outboard slice". All slices include the content chunks and intermediate hashes intermixed, as in the combined encoding mode.

This reader doesn't implement Seek, regardless of the underlying reader. In theory seeking inside a slice is possible, but in practice if you only want part of a slice, you should request a different slice with the parameters you actually want.

This implementation is single-threaded.

Example

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

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

Methods

impl<T: Read> SliceReader<T>

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

Trait Implementations

impl<T: Read> Read for SliceReader<T>

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.

unsafe fn initializer(&self) -> Initializer

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

Determines if this Reader can work with buffers of uninitialized memory.

fn read_to_end(&mut self, buf: &mut Vec<u8>) -> 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 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 chars(self) -> Chars<Self>

Deprecated since 1.27.0

: Use str::from_utf8 instead: https://doc.rust-lang.org/nightly/std/str/struct.Utf8Error.html#examples

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

the semantics of a partial read/write of where errors happen is currently unclear and may change

Transforms this Read instance to an [Iterator] over [char]s.

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

Creates an adaptor which will chain this stream with another.

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

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