Struct opendal::Writer

pub struct Writer { /* private fields */ }

Writer is designed to write data into given path in an asynchronous manner.

Notes

Please make sure either close or abort has been called before dropping the writer otherwise the data could be lost.

Usage

Write Multiple Chunks

Some services support to write multiple chunks of data into given path. Services that doesn’t support write multiple chunks will return ErrorKind::Unsupported error when calling write at the second time.

let mut w = op.writer("path/to/file").await?;
w.write(bs).await?;
w.write(bs).await?;
w.close().await?

Our writer also provides [Writer::sink] and [Writer::copy] support.

Besides, our writer implements [AsyncWrite] and [tokio::io::AsyncWrite].

Write with append enabled

Writer also supports to write with append enabled. This is useful when users want to append some data to the end of the file.

• If file doesn’t exist, it will be created and just like calling write.
• If file exists, data will be appended to the end of the file.

Possible Errors:

• Some services store normal file and appendable file in different way. Trying to append on non-appendable file could return ErrorKind::ConditionNotMatch error.
• Services that doesn’t support append will return ErrorKind::Unsupported error when creating writer with append enabled.

Implementations

impl Writer

pub async fn write(&mut self, bs: impl Into<Buffer>) -> Result<()>

Write Buffer into writer.

This operation will write all data in given buffer into writer.

Examples

use opendal::Operator;
use opendal::Result;
use bytes::Bytes;

async fn test(op: Operator) -> Result<()> {
    let mut w = op
        .writer("hello.txt")
        .await?;
    // Buffer can be created from continues bytes.
    w.write("hello, world").await?;
    // Buffer can also be created from non-continues bytes.
    w.write(vec![Bytes::from("hello,"), Bytes::from("world!")]).await?;

    // Make sure file has been written completely.
    w.close().await?;
    Ok(())
}

pub async fn write_from(&mut self, bs: impl Buf) -> Result<()>

Write [bytes::Buf] into inner writer.

This operation will write all data in given buffer into writer.

TODO

Optimize this function to avoid unnecessary copy.

pub async fn abort(&mut self) -> Result<()>

Abort the writer and clean up all written data.

Notes

Abort should only be called when the writer is not closed or aborted, otherwise an unexpected error could be returned.

pub async fn close(&mut self) -> Result<()>

Close the writer and make sure all data have been committed.

Notes

Close should only be called when the writer is not closed or aborted, otherwise an unexpected error could be returned.

pub fn into_futures_async_write(self) -> FuturesAsyncWriter

Convert writer into FuturesAsyncWriter which implements [futures::AsyncWrite],

Notes

FuturesAsyncWriter is not a zero-cost abstraction. The underlying writer requires an owned Buffer, which involves an extra copy operation.

FuturesAsyncWriters are automatically closed when they go out of scope. Errors detected on closing are ignored by the implementation of Drop. Use the method close if these errors must be manually handled.

Examples

Basic Usage

use std::io;

use futures::io::AsyncWriteExt;
use opendal::Operator;
use opendal::Result;

async fn test(op: Operator) -> io::Result<()> {
    let mut w = op
        .writer("hello.txt")
        .await?
        .into_futures_async_write();
    let bs = "Hello, World!".as_bytes();
    w.write_all(bs).await?;
    w.close().await?;

    Ok(())
}

Concurrent Write

use std::io;

use futures::io::AsyncWriteExt;
use opendal::Operator;
use opendal::Result;

async fn test(op: Operator) -> io::Result<()> {
    let mut w = op
        .writer_with("hello.txt").concurrent(8).chunk(256)
        .await?
        .into_futures_async_write();
    let bs = "Hello, World!".as_bytes();
    w.write_all(bs).await?;
    w.close().await?;

    Ok(())
}

pub fn into_bytes_sink(self) -> FuturesBytesSink

Convert writer into FuturesBytesSink which implements [futures::Sink<Bytes>].

Notes

FuturesBytesSink is a zero-cost abstraction. The underlying writer will reuse the Bytes and won’t perform any copy operation.

Examples

Basic Usage

use std::io;

use futures::SinkExt;
use opendal::Operator;
use opendal::Result;
use bytes::Bytes;

async fn test(op: Operator) -> io::Result<()> {
    let mut w = op
        .writer("hello.txt")
        .await?
        .into_bytes_sink();
    let bs = "Hello, World!".as_bytes();
    w.send(Bytes::from(bs)).await?;
    w.close().await?;

    Ok(())
}

Concurrent Write

use std::io;

use futures::SinkExt;
use opendal::Operator;
use opendal::Result;
use bytes::Bytes;

async fn test(op: Operator) -> io::Result<()> {
    let mut w = op
        .writer_with("hello.txt").concurrent(8).chunk(256)
        .await?
        .into_bytes_sink();
    let bs = "Hello, World!".as_bytes();
    w.send(Bytes::from(bs)).await?;
    w.close().await?;

    Ok(())
}