fs-err 2.2.0

/*!

fs-err is a drop-in replacement for [`std::fs`][std::fs] that provides more
helpful messages on errors. Extra information includes which operations was
attmpted and any involved paths.

# Error Messages

Using [`std::fs`][std::fs], if this code fails:

```no_run
# use std::fs::File;
let file = File::open("does not exist.txt")?;
# Ok::<(), std::io::Error>(())
```

The error message that Rust gives you isn't very useful:

```txt
The system cannot find the file specified. (os error 2)
```

...but if we use fs-err instead, our error contains more actionable information:

```txt
failed to open file `does not exist.txt`
    caused by: The system cannot find the file specified. (os error 2)
```

# Usage

fs-err's API is the same as [`std::fs`][std::fs], so migrating code to use it is easy.

```no_run
// use std::fs;
use fs_err as fs;

let contents = fs::read_to_string("foo.txt")?;

println!("Read foo.txt: {}", contents);

# Ok::<(), std::io::Error>(())
```

fs-err uses [`std::io::Error`][std::io::Error] for all errors. This helps fs-err
compose well with traits from the standard library like
[`std::io::Read`][std::io::Read] and crates that use them like
[`serde_json`][serde_json]:

```no_run
use fs_err::File;

let file = File::open("my-config.json")?;

// If an I/O error occurs inside serde_json, the error will include a file path
// as well as what operation was being performed.
let decoded: Vec<String> = serde_json::from_reader(file)?;

println!("Program config: {:?}", decoded);

# Ok::<(), Box<dyn std::error::Error>>(())
```

[std::fs]: https://doc.rust-lang.org/stable/std/fs/
[std::io::Error]: https://doc.rust-lang.org/stable/std/io/struct.Error.html
[std::io::Read]: https://doc.rust-lang.org/stable/std/io/trait.Read.html
[serde_json]: https://crates.io/crates/serde_json
*/

#![doc(html_root_url = "https://docs.rs/fs-err/2.2.0")]
#![deny(missing_debug_implementations, missing_docs)]

mod dir;
mod errors;
mod file;

use std::fs;
use std::io::{self, Read, Write};
use std::path::{Path, PathBuf};

use errors::{CopyError, Error, ErrorKind};

pub use dir::*;
pub use file::*;

/// Wrapper for [`fs::read`](https://doc.rust-lang.org/stable/std/fs/fn.read.html).
pub fn read<P: AsRef<Path> + Into<PathBuf>>(path: P) -> io::Result<Vec<u8>> {
    let mut file = File::open(path)?;
    let mut bytes = Vec::with_capacity(initial_buffer_size(&file));
    file.read_to_end(&mut bytes)?;
    Ok(bytes)
}

/// Wrapper for [`fs::read_to_string`](https://doc.rust-lang.org/stable/std/fs/fn.read_to_string.html).
pub fn read_to_string<P: AsRef<Path> + Into<PathBuf>>(path: P) -> io::Result<String> {
    let mut file = File::open(path)?;
    let mut string = String::with_capacity(initial_buffer_size(&file));
    file.read_to_string(&mut string)?;
    Ok(string)
}

/// Wrapper for [`fs::write`](https://doc.rust-lang.org/stable/std/fs/fn.write.html).
pub fn write<P: AsRef<Path> + Into<PathBuf>, C: AsRef<[u8]>>(
    path: P,
    contents: C,
) -> io::Result<()> {
    File::create(path)?.write_all(contents.as_ref())
}

/// Wrapper for [`fs::copy`](https://doc.rust-lang.org/stable/std/fs/fn.copy.html).
pub fn copy<P, Q>(from: P, to: Q) -> io::Result<u64>
where
    P: AsRef<Path> + Into<PathBuf>,
    Q: AsRef<Path> + Into<PathBuf>,
{
    fs::copy(from.as_ref(), to.as_ref()).map_err(|source| CopyError::new(source, from, to))
}

/// Wrapper for [`fs::metadata`](https://doc.rust-lang.org/stable/std/fs/fn.metadata.html).
pub fn metadata<P: AsRef<Path> + Into<PathBuf>>(path: P) -> io::Result<fs::Metadata> {
    fs::metadata(path.as_ref()).map_err(|source| Error::new(source, ErrorKind::Metadata, path))
}

fn initial_buffer_size(file: &File) -> usize {
    file.file()
        .metadata()
        .map(|m| m.len() as usize + 1)
        .unwrap_or(0)
}