Struct ChecksumWriter 

pub struct ChecksumWriter<W, H> { /* private fields */ }

Writer wrapper that updates a checksum hasher with bytes written.

The wrapped hasher is updated only after the inner writer accepts bytes. Failed writes do not update the hasher.

The checksum value is whatever the supplied Hasher reports. The Rust standard-library hashers are not specified as stable file formats and are not cryptographic digests; use this wrapper for stream instrumentation unless the chosen hasher explicitly documents stronger guarantees.

Seeking changes only the wrapped writer position. It does not rewind, subtract from, or otherwise adjust the hasher state.

Examples

use std::collections::hash_map::DefaultHasher;
use std::hash::Hasher;
use std::io::Write;

use qubit_io::ChecksumWriter;

let mut expected = DefaultHasher::new();
expected.write(b"payload");

let mut writer = ChecksumWriter::new(Vec::new(), DefaultHasher::new());
writer.write_all(b"payload")?;

assert_eq!(expected.finish(), writer.checksum());
assert_eq!(b"payload", writer.get_ref().as_slice());

Implementations

impl<W, H> ChecksumWriter<W, H>

where H: Hasher,

pub fn new(inner: W, hasher: H) -> Self

Creates a checksum writer.

Parameters

• inner: Writer to wrap.
• hasher: Hasher updated with successfully written bytes.

Returns

A new checksum writer.

pub fn checksum(&self) -> u64

Returns the current checksum value.

Returns

The value reported by Hasher::finish.

pub fn get_ref(&self) -> &W

Returns an immutable reference to the wrapped writer.

Returns

The wrapped writer reference.

pub fn get_mut(&mut self) -> &mut W

Returns a mutable reference to the wrapped writer.

Returns

The wrapped writer reference.

pub fn hasher_ref(&self) -> &H

Returns an immutable reference to the wrapped hasher.

Returns

The wrapped hasher reference.

pub fn hasher_mut(&mut self) -> &mut H

Returns a mutable reference to the wrapped hasher.

Returns

The wrapped hasher reference.

pub fn into_inner(self) -> (W, H)

Consumes this wrapper and returns the wrapped writer and hasher.

Returns

A tuple containing the wrapped writer and hasher.

Trait Implementations

impl<W, H> Seek for ChecksumWriter<W, H>

where W: Seek, H: Hasher,

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

Seeks the wrapped writer without changing the hasher state.

Parameters

• position: Target writer position.

Returns

The new writer position.

Errors

Returns the seek error reported by the wrapped writer.

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.

impl<W, H> Write for ChecksumWriter<W, H>

where W: Write, H: Hasher,

fn write(&mut self, buffer: &[u8]) -> Result<usize>

Writes a buffer into this writer, returning how many bytes were written.

fn flush(&mut self) -> Result<()>

Flushes this output stream, ensuring that all intermediately buffered contents reach their destination.

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

Like write, except that it writes from a slice of buffers.

fn is_write_vectored(&self) -> bool

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

Determines if this Writer has an efficient write_vectored implementation.

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

Attempts to write an entire buffer into this writer.

fn write_all_vectored(&mut self, bufs: &mut [IoSlice<'_>]) -> Result<(), Error>

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

Attempts to write multiple buffers into this writer.

fn write_fmt(&mut self, args: Arguments<'_>) -> Result<(), Error>

Writes a formatted string into this writer, returning any error encountered.

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

where Self: Sized,

Creates a “by reference” adapter for this instance of Write.