Struct CountWrite

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pub struct CountWrite<W> { /* private fields */ }
Expand description

A wrapper for std::io::Write (and other optional Write implementations) that counts the total number of bytes written successfully.

use std::io::{BufWriter, Write};

use count_write::CountWrite;

let vec = vec![]; // note that Vec<u8> : Write
let cw = CountWrite::from(vec);
let mut bw = BufWriter::new(cw);
write!(bw, "abc")?;
assert_eq!(bw.into_inner()?.count(), 3);

If the inner writer does not successfully write all bytes, only the successfully written bytes are counted. (This does not affect users who always use write_all, write!, etc.)

use std::io::{Result, Write};

use count_write::CountWrite;;

/// A dummy struct that only accepts half of the input into a Vec.
struct OnlyHalf;

impl Write for OnlyHalf {
    fn write(&mut self, buf: &[u8]) -> Result<usize> {
    dbg!(buf);
        Ok((buf.len() + 1) / 2)
    }

    fn flush(&mut self) -> Result<()> { Ok(()) }
}

let mut cw = CountWrite::from(OnlyHalf);
write!(cw, "abc")?; // Here, we keep retrying writing into the writer
assert_eq!(cw.count(), 3);

let mut cw = CountWrite::from(OnlyHalf);
cw.write(b"abc")?; // Here, we only write to the writer once and do not retry
assert_eq!(cw.count(), 2);

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impl<W> CountWrite<W>

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pub fn count(&self) -> u64

Returns the number of bytes successfull written so far

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pub fn into_inner(self) -> W

Extracts the inner writer, discarding this wrapper

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

Wrapper for futures_io::AsyncWrite, used in the futures-preview family

Only available with the "futures" feature

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

Attempt to write bytes from buf into the object. Read more
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fn poll_flush( self: Pin<&mut Self>, ctx: &mut Context<'_>, ) -> Poll<Result<(), Error>>

Attempt to flush the object, ensuring that any buffered data reach their destination. Read more
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fn poll_close( self: Pin<&mut Self>, ctx: &mut Context<'_>, ) -> Poll<Result<(), Error>>

Attempt to close the object. Read more
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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. Read more
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impl<W: AsyncWrite> AsyncWrite for CountWrite<W>

Wrapper for tokio_io::AsyncWrite, used in the tokio family

Only available with the "tokio" feature

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

Attempt to write bytes from buf into the object. Read more
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fn poll_flush( self: Pin<&mut Self>, ctx: &mut Context<'_>, ) -> Poll<Result<(), Error>>

Attempt to flush the object, ensuring that any buffered data reach their destination. Read more
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fn poll_shutdown( self: Pin<&mut Self>, ctx: &mut Context<'_>, ) -> Poll<Result<(), Error>>

Initiates or attempts to shut down this writer, returning success when the I/O connection has completely shut down. Read more
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fn poll_write_buf<B>( self: Pin<&mut Self>, cx: &mut Context<'_>, buf: &mut B, ) -> Poll<Result<usize, Error>>
where B: Buf, Self: Sized,

Write a Buf into this value, returning how many bytes were written. Read more
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impl<W> From<W> for CountWrite<W>

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fn from(inner: W) -> Self

Converts to this type from the input type.
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impl<W: Write> Write for CountWrite<W>

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

Writes a buffer into this writer, returning how many bytes were written. Read more
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fn flush(&mut self) -> Result<(), Error>

Flushes this output stream, ensuring that all intermediately buffered contents reach their destination. Read more
1.36.0 · Source§

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

Like write, except that it writes from a slice of buffers. Read more
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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. Read more
1.0.0 · Source§

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

Attempts to write an entire buffer into this writer. Read more
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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. Read more
1.0.0 · Source§

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

Writes a formatted string into this writer, returning any error encountered. Read more
1.0.0 · Source§

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

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

Auto Trait Implementations§

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impl<W> Freeze for CountWrite<W>
where W: Freeze,

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impl<W> RefUnwindSafe for CountWrite<W>
where W: RefUnwindSafe,

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impl<W> Send for CountWrite<W>
where W: Send,

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impl<W> Sync for CountWrite<W>
where W: Sync,

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impl<W> Unpin for CountWrite<W>
where W: Unpin,

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impl<W> UnwindSafe for CountWrite<W>
where W: UnwindSafe,

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

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for T
where T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for T
where T: ?Sized,

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

Mutably borrows from an owned value. Read more
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impl<T> From<!> for T

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fn from(t: !) -> T

Converts to this type from the input type.
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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

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fn into(self) -> U

Calls U::from(self).

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

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

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.
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impl<W> WriteBytesExt for W
where W: Write + ?Sized,

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fn write_u8(&mut self, n: u8) -> Result<(), Error>

Writes an unsigned 8 bit integer to the underlying writer. Read more
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fn write_i8(&mut self, n: i8) -> Result<(), Error>

Writes a signed 8 bit integer to the underlying writer. Read more
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fn write_u16<T>(&mut self, n: u16) -> Result<(), Error>
where T: ByteOrder,

Writes an unsigned 16 bit integer to the underlying writer. Read more
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fn write_i16<T>(&mut self, n: i16) -> Result<(), Error>
where T: ByteOrder,

Writes a signed 16 bit integer to the underlying writer. Read more
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fn write_u24<T>(&mut self, n: u32) -> Result<(), Error>
where T: ByteOrder,

Writes an unsigned 24 bit integer to the underlying writer. Read more
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fn write_i24<T>(&mut self, n: i32) -> Result<(), Error>
where T: ByteOrder,

Writes a signed 24 bit integer to the underlying writer. Read more
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fn write_u32<T>(&mut self, n: u32) -> Result<(), Error>
where T: ByteOrder,

Writes an unsigned 32 bit integer to the underlying writer. Read more
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fn write_i32<T>(&mut self, n: i32) -> Result<(), Error>
where T: ByteOrder,

Writes a signed 32 bit integer to the underlying writer. Read more
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fn write_u48<T>(&mut self, n: u64) -> Result<(), Error>
where T: ByteOrder,

Writes an unsigned 48 bit integer to the underlying writer. Read more
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fn write_i48<T>(&mut self, n: i64) -> Result<(), Error>
where T: ByteOrder,

Writes a signed 48 bit integer to the underlying writer. Read more
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fn write_u64<T>(&mut self, n: u64) -> Result<(), Error>
where T: ByteOrder,

Writes an unsigned 64 bit integer to the underlying writer. Read more
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fn write_i64<T>(&mut self, n: i64) -> Result<(), Error>
where T: ByteOrder,

Writes a signed 64 bit integer to the underlying writer. Read more
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fn write_u128<T>(&mut self, n: u128) -> Result<(), Error>
where T: ByteOrder,

Writes an unsigned 128 bit integer to the underlying writer.
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fn write_i128<T>(&mut self, n: i128) -> Result<(), Error>
where T: ByteOrder,

Writes a signed 128 bit integer to the underlying writer.
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fn write_uint<T>(&mut self, n: u64, nbytes: usize) -> Result<(), Error>
where T: ByteOrder,

Writes an unsigned n-bytes integer to the underlying writer. Read more
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fn write_int<T>(&mut self, n: i64, nbytes: usize) -> Result<(), Error>
where T: ByteOrder,

Writes a signed n-bytes integer to the underlying writer. Read more
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fn write_uint128<T>(&mut self, n: u128, nbytes: usize) -> Result<(), Error>
where T: ByteOrder,

Writes an unsigned n-bytes integer to the underlying writer. Read more
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fn write_int128<T>(&mut self, n: i128, nbytes: usize) -> Result<(), Error>
where T: ByteOrder,

Writes a signed n-bytes integer to the underlying writer. Read more
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fn write_f32<T>(&mut self, n: f32) -> Result<(), Error>
where T: ByteOrder,

Writes a IEEE754 single-precision (4 bytes) floating point number to the underlying writer. Read more
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fn write_f64<T>(&mut self, n: f64) -> Result<(), Error>
where T: ByteOrder,

Writes a IEEE754 double-precision (8 bytes) floating point number to the underlying writer. Read more