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use std::{
cmp::min,
collections::HashMap,
fs::OpenOptions,
future::Future,
io::{Cursor, Error, ErrorKind},
mem::MaybeUninit,
path::{Component, Path, PathBuf},
pin::Pin,
task::{Context, Poll},
time::SystemTime,
};
use futures_util::future::{ready, Ready};
use hyper::body::Bytes;
use tokio::{
fs::{self, File},
io::{AsyncRead, AsyncSeek, ReadBuf},
task::{spawn_blocking, JoinHandle},
};
#[cfg(windows)]
use std::os::windows::fs::OpenOptionsExt;
#[cfg(windows)]
use winapi::um::winbase::FILE_FLAG_BACKUP_SEMANTICS;
const TOKIO_READ_BUF_SIZE: usize = 8 * 1024;
/// Open file handle with metadata.
///
/// This struct exists because we want to abstract away tokio `File`, but need to use
/// `File`-specific operations to find the metadata and fill the additional fields here.
///
/// This struct is eventually converted to a `ResolvedFile`.
#[derive(Debug)]
pub struct FileWithMetadata<F = File> {
/// Open file handle.
pub handle: F,
/// Size in bytes.
pub size: u64,
/// Last modification time.
pub modified: Option<SystemTime>,
/// Whether this is a directory.
pub is_dir: bool,
}
/// Trait for a simple virtual filesystem layer.
///
/// There is only the `open` operation, hence the name `FileOpener`. In practice, `open` must also
/// collect some file metadata. (See the `FileWithMetadata` struct.)
pub trait FileOpener: Send + Sync + 'static {
/// File handle type.
type File: IntoFileAccess;
/// Future type that `open` returns.
type Future: Future<Output = Result<FileWithMetadata<Self::File>, Error>> + Send;
/// Open a file and return a `FileWithMetadata`.
///
/// It can be assumed the path is already sanitized at this point.
fn open(&self, path: &Path) -> Self::Future;
}
/// Trait that converts a file handle into something that implements `FileAccess`.
///
/// This trait is called when streaming starts, and exists as a separate step so that buffer
/// allocation doesn't have to happen until that point.
pub trait IntoFileAccess: Send + Unpin + 'static {
/// Target type that implements `FileAccess`.
type Output: FileAccess;
/// Convert into a type that implements `FileAccess`.
fn into_file_access(self) -> Self::Output;
}
/// Trait that implements all the necessary file access methods used for serving files.
///
/// This trait exists as an alternative to `AsyncRead` that returns a `Bytes` directly, potentially
/// eliminating a copy. Unlike `AsyncRead`, this does mean the implementation is responsible for
/// providing the read buffer.
pub trait FileAccess: AsyncSeek + Send + Unpin + 'static {
/// Attempts to read from the file.
///
/// If no data is available for reading, the method returns `Poll::Pending` and arranges for
/// the current task (via `cx.waker()`) to receive a notification when the object becomes
/// readable or is closed.
///
/// An empty `Bytes` return value indicates EOF.
fn poll_read(
self: Pin<&mut Self>,
cx: &mut Context<'_>,
len: usize,
) -> Poll<Result<Bytes, Error>>;
}
//
// Tokio File implementation
//
impl IntoFileAccess for File {
type Output = TokioFileAccess;
fn into_file_access(self) -> Self::Output {
TokioFileAccess::new(self)
}
}
/// Struct that wraps a tokio `File` to implement `FileAccess`.
pub struct TokioFileAccess {
file: File,
read_buf: Box<[MaybeUninit<u8>; TOKIO_READ_BUF_SIZE]>,
}
impl TokioFileAccess {
/// Create a new `TokioFileAccess` for a `File`.
pub fn new(file: File) -> Self {
TokioFileAccess {
file,
read_buf: Box::new([MaybeUninit::uninit(); TOKIO_READ_BUF_SIZE]),
}
}
}
impl AsyncSeek for TokioFileAccess {
fn start_seek(mut self: Pin<&mut Self>, position: std::io::SeekFrom) -> std::io::Result<()> {
Pin::new(&mut self.file).start_seek(position)
}
fn poll_complete(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<std::io::Result<u64>> {
Pin::new(&mut self.file).poll_complete(cx)
}
}
impl FileAccess for TokioFileAccess {
fn poll_read(
mut self: Pin<&mut Self>,
cx: &mut Context<'_>,
len: usize,
) -> Poll<Result<Bytes, Error>> {
let Self {
ref mut file,
ref mut read_buf,
} = *self;
let len = min(len, read_buf.len()) as usize;
let mut read_buf = ReadBuf::uninit(&mut read_buf[..len]);
match Pin::new(file).poll_read(cx, &mut read_buf) {
Poll::Ready(Ok(())) => {
let filled = read_buf.filled();
if filled.is_empty() {
Poll::Ready(Ok(Bytes::new()))
} else {
Poll::Ready(Ok(Bytes::copy_from_slice(filled)))
}
}
Poll::Ready(Err(e)) => Poll::Ready(Err(e)),
Poll::Pending => Poll::Pending,
}
}
}
/// Filesystem implementation that uses `tokio::fs`.
pub struct TokioFileOpener {
/// The virtual root directory to use when opening files.
///
/// The path may be absolute or relative.
pub root: PathBuf,
}
impl TokioFileOpener {
/// Create a new `TokioFileOpener` for the given root path.
///
/// The path may be absolute or relative.
pub fn new(root: impl Into<PathBuf>) -> Self {
Self { root: root.into() }
}
}
impl FileOpener for TokioFileOpener {
type File = File;
type Future = TokioFileFuture;
fn open(&self, path: &Path) -> Self::Future {
let mut full_path = self.root.clone();
full_path.extend(path);
// Small perf gain: we do open + metadata in one go. If we used the tokio async functions
// here, that'd amount to two `spawn_blocking` calls behind the scenes.
let inner = spawn_blocking(move || {
let mut opts = OpenOptions::new();
opts.read(true);
// On Windows, we need to set this flag to be able to open directories.
#[cfg(windows)]
opts.custom_flags(FILE_FLAG_BACKUP_SEMANTICS);
let handle = opts.open(full_path)?;
let metadata = handle.metadata()?;
Ok(FileWithMetadata {
handle: File::from_std(handle),
size: metadata.len(),
modified: metadata.modified().ok(),
is_dir: metadata.is_dir(),
})
});
TokioFileFuture { inner }
}
}
/// Future type produced by `TokioFileOpener`.
///
/// This type mostly exists just to prevent a `Box<dyn Future>`.
pub struct TokioFileFuture {
inner: JoinHandle<Result<FileWithMetadata<File>, Error>>,
}
impl Future for TokioFileFuture {
type Output = Result<FileWithMetadata<File>, Error>;
fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
// The task produces a result, but so does the `JoinHandle`, so this is a
// `Result<Result<..>>`. We map the `JoinHandle` error to an IO error, so that we can
// flatten the results. This is similar to what tokio does, but that just uses `Map` and
// async functions (with an anonymous future type).
match Pin::new(&mut self.inner).poll(cx) {
Poll::Ready(Ok(res)) => Poll::Ready(res),
Poll::Ready(Err(_)) => {
Poll::Ready(Err(Error::new(ErrorKind::Other, "background task failed")))
}
Poll::Pending => Poll::Pending,
}
}
}
//
// In-memory implementation
//
type MemoryFileMap = HashMap<PathBuf, FileWithMetadata<Bytes>>;
impl IntoFileAccess for Cursor<Bytes> {
type Output = Self;
fn into_file_access(self) -> Self::Output {
// No read buffer required. We can simply create subslices.
self
}
}
impl FileAccess for Cursor<Bytes> {
fn poll_read(
self: Pin<&mut Self>,
_cx: &mut Context<'_>,
len: usize,
) -> Poll<Result<Bytes, Error>> {
let pos = self.position();
let slice = (*self).get_ref();
// The position could technically be out of bounds, so don't panic...
if pos > slice.len() as u64 {
return Poll::Ready(Ok(Bytes::new()));
}
let start = pos as usize;
let amt = min(slice.len() - start, len);
// Add won't overflow because of pos check above.
let end = start + amt;
Poll::Ready(Ok(slice.slice(start..end)))
}
}
/// An in-memory virtual filesystem.
///
/// This type implements `FileOpener`, and can be directly used in `Static::with_opener`, for example.
pub struct MemoryFs {
files: MemoryFileMap,
}
impl Default for MemoryFs {
fn default() -> Self {
let mut files = MemoryFileMap::new();
// Create a top-level directory entry.
files.insert(
PathBuf::new(),
FileWithMetadata {
handle: Bytes::new(),
size: 0,
modified: None,
is_dir: true,
},
);
Self { files }
}
}
impl MemoryFs {
/// Initialize a `MemoryFs` from a directory.
///
/// This loads all files and their contents into memory. Symlinks are followed.
pub async fn from_dir(path: impl AsRef<Path>) -> Result<Self, Error> {
let mut fs = Self::default();
// Pending directories to scan, as: `(real path, virtual path)`
let mut dirs = vec![(path.as_ref().to_path_buf(), PathBuf::new())];
while let Some((dir, base)) = dirs.pop() {
let mut iter = fs::read_dir(dir).await?;
while let Some(entry) = iter.next_entry().await? {
let metadata = entry.metadata().await?;
// Build the virtual path.
let mut out_path = base.to_path_buf();
out_path.push(entry.file_name());
if metadata.is_dir() {
// Add to pending stack,
dirs.push((entry.path(), out_path));
} else if metadata.is_file() {
// Read file contents and create an entry.
let data = fs::read(entry.path()).await?;
fs.add(out_path, data.into(), metadata.modified().ok());
}
}
}
Ok(fs)
}
/// Add a file to the `MemoryFs`.
///
/// This automatically creates directory entries leading up to the path. Any existing entries
/// are overwritten.
pub fn add(
&mut self,
path: impl Into<PathBuf>,
data: Bytes,
modified: Option<SystemTime>,
) -> &mut Self {
let path = path.into();
// Create directory entries.
let mut components: Vec<_> = path.components().collect();
components.pop();
let mut dir_path = PathBuf::new();
for component in components {
if let Component::Normal(x) = component {
dir_path.push(x);
self.files.insert(
dir_path.clone(),
FileWithMetadata {
handle: Bytes::new(),
size: 0,
modified: None,
is_dir: true,
},
);
}
}
// Create the file entry.
let size = data.len() as u64;
self.files.insert(
path,
FileWithMetadata {
handle: data,
size,
modified,
is_dir: false,
},
);
self
}
}
impl FileOpener for MemoryFs {
type File = Cursor<Bytes>;
type Future = Ready<Result<FileWithMetadata<Self::File>, Error>>;
fn open(&self, path: &Path) -> Self::Future {
ready(
self.files
.get(path)
.map(|file| FileWithMetadata {
handle: Cursor::new(file.handle.clone()),
size: file.size,
modified: file.modified,
is_dir: file.is_dir,
})
.ok_or_else(|| Error::new(ErrorKind::NotFound, "Not found")),
)
}
}