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#![forbid(missing_docs)]
#![cfg_attr(test, deny(warnings))]
#![doc(test(attr(deny(warnings))))]
//! # Continuously read and write to disk, using random offsets and lengths
//! [RandomAccessDisk] is a complete implementation of [random-access-storage](https://docs.rs/random-access-storage)
//! for in-memory storage.
//!
//! See also [random-access-memory](https://docs.rs/random-access-memory) for in-memory storage
//! that can be swapped with this.
//!
//! ## Features
//!
//! ### `sparse` (default)
//!
//! Deleting may create sparse files, on by default. Creation of sparse files is tested on OSX, linux and Windows.
//!
//! **NB**: If this is on, `unsafe` code is used to make direct platform-specific calls!
//!
//! ### `async-std` (default)
//!
//! Use the async-std runtime, on by default. Either this or `tokio` is mandatory.
//!
//! ### `tokio`
//!
//! Use the tokio runtime. Either this or `async_std` is mandatory.
//!
//! ## Examples
//!
//! Reading, writing, deleting and truncating:
//!
//! ```
//! # #[cfg(feature = "tokio")]
//! # tokio_test::block_on(async {
//! # example().await;
//! # });
//! # #[cfg(feature = "async-std")]
//! # async_std::task::block_on(async {
//! # example().await;
//! # });
//! # async fn example() {
//! use random_access_storage::RandomAccess;
//! use random_access_disk::RandomAccessDisk;
//!
//! let path = tempfile::Builder::new().prefix("basic").tempfile().unwrap().into_temp_path();
//! let mut storage = RandomAccessDisk::open(path.to_path_buf()).await.unwrap();
//! storage.write(0, b"hello").await.unwrap();
//! storage.write(5, b" world").await.unwrap();
//! assert_eq!(storage.read(0, 11).await.unwrap(), b"hello world");
//! assert_eq!(storage.len().await.unwrap(), 11);
//! storage.del(5, 2).await.unwrap();
//! assert_eq!(storage.read(5, 2).await.unwrap(), [0, 0]);
//! assert_eq!(storage.len().await.unwrap(), 11);
//! storage.truncate(2).await.unwrap();
//! assert_eq!(storage.len().await.unwrap(), 2);
//! storage.truncate(5).await.unwrap();
//! assert_eq!(storage.len().await.unwrap(), 5);
//! assert_eq!(storage.read(0, 5).await.unwrap(), [b'h', b'e', 0, 0, 0]);
//! # }
//! ```
//!
//! In order to get benefits from the swappable interface, you will
//! in most cases want to use generic functions for storage manipulation:
//!
//! ```
//! # #[cfg(feature = "tokio")]
//! # tokio_test::block_on(async {
//! # example().await;
//! # });
//! # #[cfg(feature = "async-std")]
//! # async_std::task::block_on(async {
//! # example().await;
//! # });
//! # async fn example() {
//! use random_access_storage::RandomAccess;
//! use random_access_disk::RandomAccessDisk;
//! use std::fmt::Debug;
//!
//! let path = tempfile::Builder::new().prefix("swappable").tempfile().unwrap().into_temp_path();
//! let mut storage = RandomAccessDisk::open(path.to_path_buf()).await.unwrap();
//! write_hello_world(&mut storage).await;
//! assert_eq!(read_hello_world(&mut storage).await, b"hello world");
//!
//! /// Write with swappable storage
//! async fn write_hello_world<T>(storage: &mut T)
//! where T: RandomAccess + Debug + Send,
//! {
//! storage.write(0, b"hello").await.unwrap();
//! storage.write(5, b" world").await.unwrap();
//! }
//!
//! /// Read with swappable storage
//! async fn read_hello_world<T>(storage: &mut T) -> Vec<u8>
//! where T: RandomAccess + Debug + Send,
//! {
//! storage.read(0, 11).await.unwrap()
//! }
//! # }
#[cfg(not(any(feature = "async-std", feature = "tokio")))]
compile_error!(
"Either feature `random-access-disk/async-std` or `random-access-disk/tokio` must be enabled."
);
#[cfg(all(feature = "async-std", feature = "tokio"))]
compile_error!("features `random-access-disk/async-std` and `random-access-disk/tokio` are mutually exclusive");
#[cfg(feature = "async-std")]
use async_std::{
fs::{self, OpenOptions},
io::prelude::{SeekExt, WriteExt},
io::{ReadExt, SeekFrom},
};
use random_access_storage::{RandomAccess, RandomAccessError};
use std::ops::Drop;
use std::path;
#[cfg(feature = "tokio")]
use std::io::SeekFrom;
#[cfg(feature = "tokio")]
use tokio::{
fs::{self, OpenOptions},
io::{AsyncReadExt, AsyncSeekExt, AsyncWriteExt},
};
#[cfg(all(
feature = "sparse",
any(
target_os = "linux",
target_os = "android",
target_os = "freebsd",
target_os = "macos",
)
))]
mod unix;
#[cfg(all(
feature = "sparse",
any(
target_os = "linux",
target_os = "android",
target_os = "freebsd",
target_os = "macos",
)
))]
use unix::{get_length_and_block_size, set_sparse, trim};
#[cfg(all(feature = "sparse", windows))]
mod windows;
#[cfg(all(feature = "sparse", windows))]
use windows::{get_length_and_block_size, set_sparse, trim};
#[cfg(not(all(
feature = "sparse",
any(
target_os = "linux",
target_os = "android",
target_os = "freebsd",
target_os = "macos",
windows,
)
)))]
mod default;
#[cfg(not(all(
feature = "sparse",
any(
target_os = "linux",
target_os = "android",
target_os = "freebsd",
target_os = "macos",
windows,
)
)))]
use default::{get_length_and_block_size, set_sparse, trim};
/// Main constructor.
#[derive(Debug)]
pub struct RandomAccessDisk {
#[allow(dead_code)]
filename: path::PathBuf,
file: Option<fs::File>,
length: u64,
block_size: u64,
auto_sync: bool,
}
impl RandomAccessDisk {
/// Create a new (auto-sync) instance to storage at `filename`.
#[allow(clippy::new_ret_no_self)]
pub async fn open(
filename: impl AsRef<path::Path>,
) -> Result<RandomAccessDisk, RandomAccessError> {
Self::builder(filename).build().await
}
/// Initialize a builder with storage at `filename`.
pub fn builder(filename: impl AsRef<path::Path>) -> Builder {
Builder::new(filename)
}
}
#[async_trait::async_trait]
impl RandomAccess for RandomAccessDisk {
async fn write(
&mut self,
offset: u64,
data: &[u8],
) -> Result<(), RandomAccessError> {
let file = self.file.as_mut().expect("self.file was None.");
file.seek(SeekFrom::Start(offset)).await?;
file.write_all(data).await?;
if self.auto_sync {
file.sync_all().await?;
}
// We've changed the length of our file.
let new_len = offset + (data.len() as u64);
if new_len > self.length {
self.length = new_len;
}
Ok(())
}
// NOTE(yw): disabling clippy here because we files on disk might be sparse,
// and sometimes you might want to read a bit of memory to check if it's
// formatted or not. Returning zero'd out memory seems like an OK thing to do.
// We should probably come back to this at a future point, and determine
// whether it's okay to return a fully zero'd out slice. It's a bit weird,
// because we're replacing empty data with actual zeroes - which does not
// reflect the state of the world.
// #[cfg_attr(test, allow(unused_io_amount))]
async fn read(
&mut self,
offset: u64,
length: u64,
) -> Result<Vec<u8>, RandomAccessError> {
if offset + length > self.length {
return Err(RandomAccessError::OutOfBounds {
offset,
end: Some(offset + length),
length: self.length,
});
}
let file = self.file.as_mut().expect("self.file was None.");
let mut buffer = vec![0; length as usize];
file.seek(SeekFrom::Start(offset)).await?;
let _bytes_read = file.read(&mut buffer[..]).await?;
Ok(buffer)
}
async fn del(
&mut self,
offset: u64,
length: u64,
) -> Result<(), RandomAccessError> {
if offset > self.length {
return Err(RandomAccessError::OutOfBounds {
offset,
end: None,
length: self.length,
});
};
if length == 0 {
// No-op
return Ok(());
}
// Delete is truncate if up to the current length or more is deleted
if offset + length >= self.length {
return self.truncate(offset).await;
}
let file = self.file.as_mut().expect("self.file was None.");
trim(file, offset, length, self.block_size).await?;
if self.auto_sync {
file.sync_all().await?;
}
Ok(())
}
async fn truncate(&mut self, length: u64) -> Result<(), RandomAccessError> {
let file = self.file.as_ref().expect("self.file was None.");
self.length = length;
file.set_len(self.length).await?;
if self.auto_sync {
file.sync_all().await?;
}
Ok(())
}
async fn len(&mut self) -> Result<u64, RandomAccessError> {
Ok(self.length)
}
async fn is_empty(&mut self) -> Result<bool, RandomAccessError> {
Ok(self.length == 0)
}
async fn sync_all(&mut self) -> Result<(), RandomAccessError> {
if !self.auto_sync {
let file = self.file.as_ref().expect("self.file was None.");
file.sync_all().await?;
}
Ok(())
}
}
impl Drop for RandomAccessDisk {
fn drop(&mut self) {
// We need to flush the file on drop. Unfortunately, that is not possible to do in a
// non-blocking fashion, but our only other option here is losing data remaining in the
// write cache. Good task schedulers should be resilient to occasional blocking hiccups in
// file destructors so we don't expect this to be a common problem in practice.
// (from async_std::fs::File::drop)
#[cfg(feature = "async-std")]
if let Some(file) = &self.file {
let _ = async_std::task::block_on(file.sync_all());
}
// For tokio, the below errors with:
//
// "Cannot start a runtime from within a runtime. This happens because a function (like
// `block_on`) attempted to block the current thread while the thread is being used to
// drive asynchronous tasks."
//
// There doesn't seem to be an equivalent block_on version for tokio that actually works
// in a sync drop(), so for tokio, we'll need to wait for a real AsyncDrop to arrive.
//
// #[cfg(feature = "tokio")]
// if let Some(file) = &self.file {
// tokio::runtime::Handle::current()
// .block_on(file.sync_all())
// .expect("Could not sync file changes on drop.");
// }
}
}
/// Builder for [RandomAccessDisk]
pub struct Builder {
filename: path::PathBuf,
auto_sync: bool,
}
impl Builder {
/// Create new builder at `path` (with auto-sync true by default).
pub fn new(filename: impl AsRef<path::Path>) -> Self {
Self {
filename: filename.as_ref().into(),
auto_sync: true,
}
}
/// Set auto-sync
// NB: Because of no AsyncDrop, tokio can not ensure that changes are synced when dropped,
// see impl Drop above.
#[cfg(feature = "async-std")]
pub fn auto_sync(mut self, auto_sync: bool) -> Self {
self.auto_sync = auto_sync;
self
}
/// Build a [RandomAccessDisk] instance
pub async fn build(self) -> Result<RandomAccessDisk, RandomAccessError> {
if let Some(dirname) = self.filename.parent() {
mkdirp::mkdirp(dirname)?;
}
let mut file = OpenOptions::new()
.create(true)
.read(true)
.write(true)
.open(&self.filename)
.await?;
file.sync_all().await?;
set_sparse(&mut file).await?;
let (length, block_size) = get_length_and_block_size(&file).await?;
Ok(RandomAccessDisk {
filename: self.filename,
file: Some(file),
length,
auto_sync: self.auto_sync,
block_size,
})
}
}