Struct Counter 

pub struct Counter<D> { /* private fields */ }

A wrapper that adds byte counting functionality to any reader, writer, or seeker.

Counter<D> tracks the total number of bytes read from and written to the underlying I/O object, providing methods to query these statistics at any time.

Type Parameter

• D - The underlying I/O object (reader, writer, or seeker)

Examples

Basic Usage with std::io

use std::io::{Read, Write};
use countio::Counter;

// Counting bytes read
let data = b"Hello, World!";
let mut reader = Counter::new(&data[..]);
let mut buffer = [0u8; 5];
reader.read(&mut buffer).unwrap();
assert_eq!(reader.reader_bytes(), 5);

// Counting bytes written
let mut writer = Counter::new(Vec::new());
writer.write_all(b"Hello").unwrap();
assert_eq!(writer.writer_bytes(), 5);

With Buffered I/O

use std::io::{BufRead, BufReader, BufWriter, Write};
use countio::Counter;

// Buffered reading
let data = "Line 1\nLine 2\nLine 3\n";
let reader = BufReader::new(data.as_bytes());
let mut counter = Counter::new(reader);
let mut line = String::new();
counter.read_line(&mut line).unwrap();
assert_eq!(counter.reader_bytes(), 7);

// Buffered writing
let writer = BufWriter::new(Vec::new());
let mut counter = Counter::new(writer);
counter.write_all(b"Hello, World!").unwrap();
counter.flush().unwrap();
assert_eq!(counter.writer_bytes(), 13);

Performance

The overhead of byte counting is minimal - just an integer addition per I/O operation. The wrapper implements all relevant traits (Read, Write, Seek, etc.) by delegating to the inner object while tracking byte counts.

Implementations

impl<D> Counter<D>

pub const fn new(inner: D) -> Self

Creates a new Counter<D> wrapping the given I/O object with zero read/written bytes.

Arguments

• inner - The I/O object to wrap (reader, writer, seeker, etc.)

Examples

use countio::Counter;
use std::io::Cursor;

let data = vec![1, 2, 3, 4, 5];
let cursor = Cursor::new(data);
let counter = Counter::new(cursor);

assert_eq!(counter.reader_bytes(), 0);
assert_eq!(counter.writer_bytes(), 0);

pub const fn with_bytes( inner: D, reader_bytes: usize, writer_bytes: usize, ) -> Self

Creates a new Counter<D> with pre-existing read/written byte counts.

This is useful when you want to continue counting from a previous session or when wrapping an I/O object that has already processed some data.

Arguments

• inner - The I/O object to wrap
• reader_bytes - Initial count of bytes read
• writer_bytes - Initial count of bytes written

Examples

use countio::Counter;
use std::io::Cursor;

let data = vec![1, 2, 3, 4, 5];
let cursor = Cursor::new(data);
let counter = Counter::with_bytes(cursor, 100, 50);

assert_eq!(counter.reader_bytes(), 100);
assert_eq!(counter.writer_bytes(), 50);

pub const fn reader_bytes(&self) -> usize

Returns the total number of bytes read from the underlying I/O object.

This count includes all bytes successfully read through any of the Read or BufRead trait methods.

Examples

use std::io::Read;
use countio::Counter;

let data = b"Hello, World!";
let mut reader = Counter::new(&data[..]);
let mut buffer = [0u8; 5];

reader.read_exact(&mut buffer).unwrap();
assert_eq!(reader.reader_bytes(), 5);
assert_eq!(reader.writer_bytes(), 0);

pub const fn writer_bytes(&self) -> usize

Returns the total number of bytes written to the underlying I/O object.

This count includes all bytes successfully written through any of the Write trait methods.

Examples

use std::io::Write;
use countio::Counter;

let mut writer = Counter::new(Vec::new());
writer.write_all(b"Hello").unwrap();
writer.write_all(b", World!").unwrap();

assert_eq!(writer.writer_bytes(), 13);
assert_eq!(writer.reader_bytes(), 0);

pub const fn total_bytes(&self) -> u128

Returns the total number of bytes processed (read + written) as a u128.

This is the sum of all bytes that have been read from or written to the underlying I/O object since the Counter was created. Using u128 prevents overflow issues that could occur with large byte counts.

Examples

use std::io::{Read, Write};
use countio::Counter;

let mut counter = Counter::new(Vec::new());
counter.write_all(b"Hello").unwrap();

let data = b"World";
let mut reader = Counter::new(&data[..]);
let mut buf = [0u8; 5];
reader.read(&mut buf).unwrap();

assert_eq!(counter.total_bytes(), 5);
assert_eq!(reader.total_bytes(), 5);

pub fn into_inner(self) -> D

Consumes the Counter<D> and returns the underlying I/O object.

This is useful when you need to recover the original I/O object, perhaps to pass it to code that doesn’t know about the Counter wrapper.

Examples

use std::io::Write;
use countio::Counter;

let original_writer = Vec::new();
let mut counter = Counter::new(original_writer);
counter.write_all(b"Hello").unwrap();

let recovered_writer = counter.into_inner();
assert_eq!(recovered_writer, b"Hello");

pub const fn get_ref(&self) -> &D

Gets a reference to the underlying I/O object.

This allows you to access the wrapped object’s methods directly without consuming the Counter.

Examples

use countio::Counter;
use std::io::Cursor;

let data = vec![1, 2, 3, 4, 5];
let cursor = Cursor::new(data.clone());
let counter = Counter::new(cursor);

assert_eq!(counter.get_ref().position(), 0);

pub const fn get_mut(&mut self) -> &mut D

Gets a mutable reference to the underlying I/O object.

This allows you to modify the wrapped object directly. Note that any bytes read or written through the direct reference will not be counted by the Counter.

Examples

use countio::Counter;
use std::io::Cursor;

let data = vec![1, 2, 3, 4, 5];
let cursor = Cursor::new(data);
let mut counter = Counter::new(cursor);

counter.get_mut().set_position(2);
assert_eq!(counter.get_ref().position(), 2);

pub const fn reset(&mut self)

Resets the byte counters to zero without affecting the underlying I/O object.

This is useful when you want to start counting from a fresh state without recreating the wrapper or losing the underlying object’s state.

Examples

use std::io::{Read, Write};
use countio::Counter;

let mut counter = Counter::new(Vec::new());
counter.write_all(b"Hello").unwrap();
assert_eq!(counter.writer_bytes(), 5);

counter.reset();
assert_eq!(counter.writer_bytes(), 0);
assert_eq!(counter.reader_bytes(), 0);

// The underlying data is preserved
assert_eq!(counter.get_ref(), b"Hello");

Trait Implementations

impl<R: AsyncBufRead + Unpin> AsyncBufRead for Counter<R>

Available on crate feature futures only.

fn poll_fill_buf( self: Pin<&mut Self>, ctx: &mut Context<'_>, ) -> Poll<Result<&[u8]>>

Attempt to return the contents of the internal buffer, filling it with more data from the inner reader if it is empty.

fn consume(self: Pin<&mut Self>, amt: usize)

Tells this buffer that amt bytes have been consumed from the buffer, so they should no longer be returned in calls to poll_read.

impl<R: AsyncBufRead + Unpin> AsyncBufRead for Counter<R>

Available on crate feature tokio only.

fn poll_fill_buf( self: Pin<&mut Self>, ctx: &mut Context<'_>, ) -> Poll<Result<&[u8]>>

Attempts to return the contents of the internal buffer, filling it with more data from the inner reader if it is empty.

fn consume(self: Pin<&mut Self>, amt: usize)

Tells this buffer that amt bytes have been consumed from the buffer, so they should no longer be returned in calls to poll_read.

impl<R: AsyncRead + Unpin> AsyncRead for Counter<R>

Available on crate feature futures only.

fn poll_read( self: Pin<&mut Self>, ctx: &mut Context<'_>, buf: &mut [u8], ) -> Poll<Result<usize>>

Attempt to read from the AsyncRead into buf.

fn poll_read_vectored( self: Pin<&mut Self>, cx: &mut Context<'_>, bufs: &mut [IoSliceMut<'_>], ) -> Poll<Result<usize, Error>>

Attempt to read from the AsyncRead into bufs using vectored IO operations.

impl<R: AsyncRead + Unpin> AsyncRead for Counter<R>

Available on crate feature tokio only.

fn poll_read( self: Pin<&mut Self>, ctx: &mut Context<'_>, buf: &mut ReadBuf<'_>, ) -> Poll<Result<()>>

Attempts to read from the AsyncRead into buf.

impl<D: AsyncSeek + Unpin> AsyncSeek for Counter<D>

Available on crate feature futures only.

fn poll_seek( self: Pin<&mut Self>, ctx: &mut Context<'_>, pos: SeekFrom, ) -> Poll<Result<u64>>

Attempt to seek to an offset, in bytes, in a stream.

impl<D: AsyncSeek + Unpin> AsyncSeek for Counter<D>

Available on crate feature tokio only.

fn start_seek(self: Pin<&mut Self>, position: SeekFrom) -> Result<()>

Attempts to seek to an offset, in bytes, in a stream.

fn poll_complete( self: Pin<&mut Self>, ctx: &mut Context<'_>, ) -> Poll<Result<u64>>

Waits for a seek operation to complete.

impl<W: AsyncWrite + Unpin> AsyncWrite for Counter<W>

Available on crate feature futures only.

fn poll_write( self: Pin<&mut Self>, ctx: &mut Context<'_>, buf: &[u8], ) -> Poll<Result<usize>>

Attempt to write bytes from buf into the object.

fn poll_flush(self: Pin<&mut Self>, ctx: &mut Context<'_>) -> Poll<Result<()>>

Attempt to flush the object, ensuring that any buffered data reach their destination.

fn poll_close(self: Pin<&mut Self>, ctx: &mut Context<'_>) -> Poll<Result<()>>

Attempt to close the object.

fn poll_write_vectored( self: Pin<&mut Self>, cx: &mut Context<'_>, bufs: &[IoSlice<'_>], ) -> Poll<Result<usize, Error>>

Attempt to write bytes from bufs into the object using vectored IO operations.

impl<W: AsyncWrite + Unpin> AsyncWrite for Counter<W>

Available on crate feature tokio only.

fn poll_write( self: Pin<&mut Self>, ctx: &mut Context<'_>, buf: &[u8], ) -> Poll<Result<usize>>

Attempt to write bytes from buf into the object.

fn poll_flush(self: Pin<&mut Self>, ctx: &mut Context<'_>) -> Poll<Result<()>>

Attempts to flush the object, ensuring that any buffered data reach their destination.

fn poll_shutdown( self: Pin<&mut Self>, ctx: &mut Context<'_>, ) -> Poll<Result<()>>

Initiates or attempts to shut down this writer, returning success when the I/O connection has completely shut down.

fn poll_write_vectored( self: Pin<&mut Self>, cx: &mut Context<'_>, bufs: &[IoSlice<'_>], ) -> Poll<Result<usize, Error>>

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

fn is_write_vectored(&self) -> bool

Determines if this writer has an efficient poll_write_vectored implementation.

impl<R: BufRead> BufRead for Counter<R>

Available on crate feature std only.

fn fill_buf(&mut self) -> Result<&[u8]>

Returns the contents of the internal buffer, filling it with more data, via Read methods, if empty.

fn consume(&mut self, amt: usize)

Marks the given amount of additional bytes from the internal buffer as having been read. Subsequent calls to read only return bytes that have not been marked as read.

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

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

Checks if there is any data left to be read.

fn read_until(&mut self, byte: u8, buf: &mut Vec<u8>) -> Result<usize, Error>

Reads all bytes into buf until the delimiter byte or EOF is reached.

fn skip_until(&mut self, byte: u8) -> Result<usize, Error>

Skips all bytes until the delimiter byte or EOF is reached.

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

Reads all bytes until a newline (the 0xA byte) is reached, and append them to the provided String buffer.

fn split(self, byte: u8) -> Split<Self>

where Self: Sized,

Returns an iterator over the contents of this reader split on the byte byte.

fn lines(self) -> Lines<Self>

where Self: Sized,

Returns an iterator over the lines of this reader.

impl<D: Clone> Clone for Counter<D>

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<D: Debug> Debug for Counter<D>

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

Formats the value using the given formatter.

impl<D: Default> Default for Counter<D>

fn default() -> Self

Returns the “default value” for a type.

impl<D> From<Counter<D>> for Progress<D>

fn from(counter: Counter<D>) -> Self

Converts to this type from the input type.

impl<D> From<D> for Counter<D>

fn from(inner: D) -> Self

Converts to this type from the input type.

impl<R: Read> Read for Counter<R>

Available on crate feature std only.

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.

fn read_array<const N: usize>(&mut self) -> Result<[u8; N], Error>

where Self: Sized,

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

Read and return a fixed array of bytes from this source.

impl<D: Seek> Seek for Counter<D>

Available on crate feature std only.

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

Seek to an offset, in bytes, in a stream.

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: Write> Write for Counter<W>

Available on crate feature std only.

fn write(&mut self, buf: &[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.