Hi folks,
I could really use some help here and feel like I must be missing something crucial.
I'm trying to create a dyn AsyncWrite + Send + Unpin from a GzEncoder for a given File.
First approach
Consider the following code:
use std::path::PathBuf;
use tokio::fs::create_dir_all;
use tokio::{
fs::OpenOptions,
io::{stderr, stdout, AsyncWrite, BufWriter},
};
use flate2::write::GzEncoder;
use flate2::Compression;
use std::io::Result;
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
enum SupportedCompression {
Uncompressed,
Gzip,
}
async fn create_writer(
path: &Option<PathBuf>,
append: bool,
compression: SupportedCompression,
use_stdout: bool,
) -> Result<(Box<dyn AsyncWrite + Unpin + Send>, bool)> {
if let Some(path) = path {
let parent = path.parent();
if let Some(parent) = parent {
// make sure parent dir structure exists
create_dir_all(parent).await?;
}
let mut file = OpenOptions::new()
.write(true)
.create(true)
.append(append)
.open(path)
.await?;
match compression {
SupportedCompression::Uncompressed => {
let writer = BufWriter::with_capacity(128 * 1024, file);
Ok((Box::new(writer), true))
}
SupportedCompression::Gzip => {
//let file = file.into_std().await;
let writer = GzEncoder::new(file, Compression::default());
Ok((Box::new(writer), true))
}
}
} else {
if use_stdout {
Ok((Box::new(stdout()), false))
} else {
Ok((Box::new(stderr()), false))
}
}
}
Errors
This does not compile and causes the following errors:
error[E0277]: the trait bound `tokio::fs::File: std::io::Write` is not satisfied
--> src/lib.rs:43:30
|
43 | let writer = GzEncoder::new(file, Compression::default());
| ^^^^^^^^^^^^^^ the trait `std::io::Write` is not implemented for `tokio::fs::File`
|
= note: required by `flate2::write::GzEncoder::<W>::new`
error[E0277]: the trait bound `tokio::fs::File: std::io::Write` is not satisfied
--> src/lib.rs:43:30
|
43 | let writer = GzEncoder::new(file, Compression::default());
| ^^^^^^^^^ the trait `std::io::Write` is not implemented for `tokio::fs::File`
|
::: /playground/.cargo/registry/src/github.com-1ecc6299db9ec823/flate2-1.0.20/src/gz/write.rs:39:25
|
39 | pub struct GzEncoder<W: Write> {
| ----- required by this bound in `flate2::write::GzEncoder`
error[E0277]: the trait bound `tokio::fs::File: std::io::Write` is not satisfied
--> src/lib.rs:43:30
|
43 | let writer = GzEncoder::new(file, Compression::default());
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `std::io::Write` is not implemented for `tokio::fs::File`
|
::: /playground/.cargo/registry/src/github.com-1ecc6299db9ec823/flate2-1.0.20/src/gz/write.rs:39:25
|
39 | pub struct GzEncoder<W: Write> {
| ----- required by this bound in `flate2::write::GzEncoder`
error[E0277]: the trait bound `tokio::fs::File: std::io::Write` is not satisfied
--> src/lib.rs:44:30
|
44 | Ok((Box::new(writer), true))
| ^^^^^^ the trait `std::io::Write` is not implemented for `tokio::fs::File`
|
::: /playground/.cargo/registry/src/github.com-1ecc6299db9ec823/flate2-1.0.20/src/gz/write.rs:39:25
|
39 | pub struct GzEncoder<W: Write> {
| ----- required by this bound in `flate2::write::GzEncoder`
error[E0277]: the trait bound `flate2::write::GzEncoder<tokio::fs::File>: AsyncWrite` is not satisfied
--> src/lib.rs:44:21
|
44 | Ok((Box::new(writer), true))
| ^^^^^^^^^^^^^^^^ the trait `AsyncWrite` is not implemented for `flate2::write::GzEncoder<tokio::fs::File>`
|
= note: required for the cast to the object type `dyn AsyncWrite + Send + Unpin`
error[E0277]: the trait bound `tokio::fs::File: std::io::Write` is not satisfied
--> src/lib.rs:44:21
|
44 | Ok((Box::new(writer), true))
| ^^^^^^^^^^^^^^^^ the trait `std::io::Write` is not implemented for `tokio::fs::File`
|
::: /playground/.cargo/registry/src/github.com-1ecc6299db9ec823/flate2-1.0.20/src/gz/write.rs:39:25
|
39 | pub struct GzEncoder<W: Write> {
| ----- required by this bound in `flate2::write::GzEncoder`
Alternative approach
If I uncomment the let file = file.into_std().await; line, it fails with this error instead:
Error
error[E0277]: the trait bound `flate2::write::GzEncoder<std::fs::File>: AsyncWrite` is not satisfied
--> src/lib.rs:44:21
|
44 | Ok((Box::new(writer), true))
| ^^^^^^^^^^^^^^^^ the trait `AsyncWrite` is not implemented for `flate2::write::GzEncoder<std::fs::File>`
|
= note: required for the cast to the object type `dyn AsyncWrite + Send + Unpin`
Help! I'm really stuck!
The errors for both approaches make sense and I understand what they are saying...
I just fail to see how I can actually create a dyn AsyncWrite + Send + Unpin from a GzEncoder for a given file.
I'm trying to find a solution to this problem for quite a while now and suspect that I'm simply unaware of a very simple way out of this mess.
Any help would be appreciated!