Struct blake3::OutputReader

source ·
pub struct OutputReader { /* private fields */ }
Expand description

An incremental reader for extended output, returned by Hasher::finalize_xof.

Shorter BLAKE3 outputs are prefixes of longer ones, and explicitly requesting a short output is equivalent to truncating the default-length output. Note that this is a difference between BLAKE2 and BLAKE3.

§Security notes

Outputs shorter than the default length of 32 bytes (256 bits) provide less security. An N-bit BLAKE3 output is intended to provide N bits of first and second preimage resistance and N/2 bits of collision resistance, for any N up to 256. Longer outputs don’t provide any additional security.

Avoid relying on the secrecy of the output offset, that is, the number of output bytes read or the arguments to seek or set_position. Block-Cipher-Based Tree Hashing by Aldo Gunsing shows that an attacker who knows both the message and the key (if any) can easily determine the offset of an extended output. For comparison, AES-CTR has a similar property: if you know the key, you can decrypt a block from an unknown position in the output stream to recover its block index. Callers with strong secret keys aren’t affected in practice, but secret offsets are a design smell in any case.

Implementations§

source§

impl OutputReader

source

pub fn fill(&mut self, buf: &mut [u8])

Fill a buffer with output bytes and advance the position of the OutputReader. This is equivalent to Read::read, except that it doesn’t return a Result. Both methods always fill the entire buffer.

Note that OutputReader doesn’t buffer output bytes internally, so calling fill repeatedly with a short-length or odd-length slice will end up performing the same compression multiple times. If you’re reading output in a loop, prefer a slice length that’s a multiple of 64.

The maximum output size of BLAKE3 is 264-1 bytes. If you try to extract more than that, for example by seeking near the end and reading further, the behavior is unspecified.

source

pub fn position(&self) -> u64

Return the current read position in the output stream. This is equivalent to Seek::stream_position, except that it doesn’t return a Result. The position of a new OutputReader starts at 0, and each call to fill or Read::read moves the position forward by the number of bytes read.

source

pub fn set_position(&mut self, position: u64)

Seek to a new read position in the output stream. This is equivalent to calling Seek::seek with SeekFrom::Start, except that it doesn’t return a Result.

Trait Implementations§

source§

impl Clone for OutputReader

source§

fn clone(&self) -> OutputReader

Returns a copy of the value. Read more
1.0.0 · source§

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more
source§

impl Debug for OutputReader

source§

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more
source§

impl Read for OutputReader

source§

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. Read more
1.36.0 · source§

fn read_vectored(&mut self, bufs: &mut [IoSliceMut<'_>]) -> Result<usize, Error>

Like read, except that it reads into a slice of buffers. Read more
source§

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. Read more
1.0.0 · source§

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. Read more
1.0.0 · source§

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

Reads all bytes until EOF in this source, appending them to buf. Read more
1.6.0 · source§

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

Reads the exact number of bytes required to fill buf. Read more
source§

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. Read more
source§

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. Read more
1.0.0 · source§

fn by_ref(&mut self) -> &mut Self
where Self: Sized,

Creates a “by reference” adaptor for this instance of Read. Read more
1.0.0 · source§

fn bytes(self) -> Bytes<Self>
where Self: Sized,

Transforms this Read instance to an Iterator over its bytes. Read more
1.0.0 · source§

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

Creates an adapter which will chain this stream with another. Read more
1.0.0 · source§

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

Creates an adapter which will read at most limit bytes from it. Read more
source§

impl Seek for OutputReader

source§

fn seek(&mut self, pos: SeekFrom) -> Result<u64>

Seek to an offset, in bytes, in a stream. Read more
1.55.0 · source§

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

Rewind to the beginning of a stream. Read more
source§

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). Read more
1.51.0 · source§

fn stream_position(&mut self) -> Result<u64, Error>

Returns the current seek position from the start of the stream. Read more
1.80.0 · source§

fn seek_relative(&mut self, offset: i64) -> Result<(), Error>

Seeks relative to the current position. Read more
source§

impl XofReader for OutputReader

source§

fn read(&mut self, buffer: &mut [u8])

Read output into the buffer. Can be called an unlimited number of times.
source§

fn read_boxed(&mut self, n: usize) -> Box<[u8]>

Read output into a boxed slice of the specified size. Read more

Auto Trait Implementations§

Blanket Implementations§

source§

impl<T> Any for T
where T: 'static + ?Sized,

source§

fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
source§

impl<T> Borrow<T> for T
where T: ?Sized,

source§

fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
source§

impl<T> BorrowMut<T> for T
where T: ?Sized,

source§

fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
source§

impl<T> CloneToUninit for T
where T: Clone,

source§

unsafe fn clone_to_uninit(&self, dst: *mut T)

🔬This is a nightly-only experimental API. (clone_to_uninit)
Performs copy-assignment from self to dst. Read more
source§

impl<T> From<T> for T

source§

fn from(t: T) -> T

Returns the argument unchanged.

source§

impl<T, U> Into<U> for T
where U: From<T>,

source§

fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

source§

impl<T> Pointable for T

source§

const ALIGN: usize = _

The alignment of pointer.
source§

type Init = T

The type for initializers.
source§

unsafe fn init(init: <T as Pointable>::Init) -> usize

Initializes a with the given initializer. Read more
source§

unsafe fn deref<'a>(ptr: usize) -> &'a T

Dereferences the given pointer. Read more
source§

unsafe fn deref_mut<'a>(ptr: usize) -> &'a mut T

Mutably dereferences the given pointer. Read more
source§

unsafe fn drop(ptr: usize)

Drops the object pointed to by the given pointer. Read more
source§

impl<T> Same for T

source§

type Output = T

Should always be Self
source§

impl<T> ToOwned for T
where T: Clone,

source§

type Owned = T

The resulting type after obtaining ownership.
source§

fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
source§

fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
source§

impl<T, U> TryFrom<U> for T
where U: Into<T>,

source§

type Error = Infallible

The type returned in the event of a conversion error.
source§

fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
source§

impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

source§

type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
source§

fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.