wist-shared 0.1.3

Shared runtime helpers for the wist ecosystem: filesystem, ids, paths, time, and primitives
Documentation 
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//! Shared filesystem helpers.

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

use serde::Serialize;
use serde::de::DeserializeOwned;

pub fn ensure_parent(path: &Path) -> io::Result<()> {
    if let Some(parent) = path.parent() {
        fs::create_dir_all(parent)?;
    }
    Ok(())
}

pub fn read_json<T>(path: &Path) -> io::Result<T>
where
    T: DeserializeOwned,
{
    let text = fs::read_to_string(path)?;
    serde_json::from_str(&text).map_err(io::Error::other)
}

pub fn write_json_atomic<T>(path: &Path, value: &T) -> io::Result<()>
where
    T: Serialize,
{
    let bytes = serde_json::to_vec_pretty(value).map_err(io::Error::other)?;
    write_bytes_atomic(path, &bytes)
}

pub fn write_json_private_atomic<T>(path: &Path, value: &T) -> io::Result<()>
where
    T: Serialize,
{
    let bytes = serde_json::to_vec_pretty(value).map_err(io::Error::other)?;
    write_bytes_private_atomic(path, &bytes)
}

pub fn write_json_compact_atomic<T>(path: &Path, value: &T) -> io::Result<()>
where
    T: Serialize,
{
    let bytes = serde_json::to_vec(value).map_err(io::Error::other)?;
    write_bytes_atomic(path, &bytes)
}

pub fn write_bytes_atomic(path: &Path, bytes: &[u8]) -> io::Result<()> {
    ensure_parent(path)?;

    let tmp_path = path.with_extension("tmp");
    let mut file = File::create(&tmp_path)?;
    file.write_all(bytes)?;
    file.write_all(b"\n")?;
    file.sync_all()?;
    drop(file);

    fs::rename(&tmp_path, path)?;
    sync_parent_dir(path)?;
    Ok(())
}

#[cfg(unix)]
pub fn write_bytes_private_atomic(path: &Path, bytes: &[u8]) -> io::Result<()> {
    use std::fs::OpenOptions;
    use std::os::unix::fs::{OpenOptionsExt, PermissionsExt};

    ensure_parent(path)?;
    if let Some(parent) = path.parent() {
        fs::set_permissions(parent, fs::Permissions::from_mode(0o700))?;
    }

    let tmp_path = path.with_extension("tmp");
    let mut file = OpenOptions::new()
        .create(true)
        .truncate(true)
        .write(true)
        .mode(0o600)
        .open(&tmp_path)?;
    file.write_all(bytes)?;
    file.write_all(b"\n")?;
    file.sync_all()?;
    drop(file);

    fs::rename(&tmp_path, path)?;
    fs::set_permissions(path, fs::Permissions::from_mode(0o600))?;
    sync_parent_dir(path)?;
    Ok(())
}

#[cfg(not(unix))]
pub fn write_bytes_private_atomic(path: &Path, bytes: &[u8]) -> io::Result<()> {
    write_bytes_atomic(path, bytes)
}

#[cfg(unix)]
fn sync_parent_dir(path: &Path) -> io::Result<()> {
    if let Some(parent) = path.parent() {
        File::open(parent)?.sync_all()?;
    }
    Ok(())
}

#[cfg(not(unix))]
fn sync_parent_dir(_path: &Path) -> io::Result<()> {
    Ok(())
}