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// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements. See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership. The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License. You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied. See the License for the
// specific language governing permissions and limitations
// under the License.
use std::collections::Bound;
use std::ops::Range;
use std::ops::RangeBounds;
use std::sync::Arc;
use bytes::BufMut;
use crate::raw::*;
use crate::*;
/// BlockingReader is designed to read data from given path in an blocking
/// manner.
#[derive(Clone)]
pub struct BlockingReader {
ctx: Arc<ReadContext>,
/// Total size of the reader.
size: Arc<AtomicContentLength>,
}
impl BlockingReader {
/// Create a new blocking reader.
///
/// Create will use internal information to decide the most suitable
/// implementation for users.
///
/// We don't want to expose those details to users so keep this function
/// in crate only.
pub(crate) fn new(ctx: ReadContext) -> Self {
BlockingReader {
ctx: Arc::new(ctx),
size: Arc::new(AtomicContentLength::new()),
}
}
/// Parse users input range bounds into valid `Range<u64>`.
///
/// To avoid duplicated stat call, we will cache the size of the reader.
fn parse_range(&self, range: impl RangeBounds<u64>) -> Result<Range<u64>> {
let start = match range.start_bound() {
Bound::Included(v) => *v,
Bound::Excluded(v) => v + 1,
Bound::Unbounded => 0,
};
let end = match range.end_bound() {
Bound::Included(v) => v + 1,
Bound::Excluded(v) => *v,
Bound::Unbounded => match self.size.load() {
Some(v) => v,
None => {
let size = self
.ctx
.accessor()
.blocking_stat(self.ctx.path(), OpStat::new())?
.into_metadata()
.content_length();
self.size.store(size);
size
}
},
};
Ok(start..end)
}
/// Read give range from reader into [`Buffer`].
///
/// This operation is zero-copy, which means it keeps the [`bytes::Bytes`] returned by underlying
/// storage services without any extra copy or intensive memory allocations.
///
/// # Notes
///
/// - Buffer length smaller than range means we have reached the end of file.
pub fn read(&self, range: impl RangeBounds<u64>) -> Result<Buffer> {
let mut bufs = vec![];
for buf in self.clone().into_iterator(range)? {
bufs.push(buf?)
}
Ok(bufs.into_iter().flatten().collect())
}
///
/// This operation will copy and write bytes into given [`BufMut`]. Allocation happens while
/// [`BufMut`] doesn't have enough space.
///
/// # Notes
///
/// - Returning length smaller than range means we have reached the end of file.
pub fn read_into(&self, buf: &mut impl BufMut, range: impl RangeBounds<u64>) -> Result<usize> {
let mut iter = self.clone().into_iterator(range)?;
let mut read = 0;
loop {
let Some(bs) = iter.next().transpose()? else {
return Ok(read);
};
read += bs.len();
buf.put(bs);
}
}
/// Create a buffer iterator to read specific range from given reader.
fn into_iterator(self, range: impl RangeBounds<u64>) -> Result<BufferIterator> {
let range = self.parse_range(range)?;
Ok(BufferIterator::new(self.ctx, range))
}
/// Convert reader into [`StdReader`] which implements [`futures::AsyncRead`],
/// [`futures::AsyncSeek`] and [`futures::AsyncBufRead`].
#[inline]
pub fn into_std_read(self, range: impl RangeBounds<u64>) -> Result<StdReader> {
let range = self.parse_range(range)?;
Ok(StdReader::new(self.ctx, range))
}
/// Convert reader into [`StdBytesIterator`] which implements [`Iterator`].
#[inline]
pub fn into_bytes_iterator(self, range: impl RangeBounds<u64>) -> Result<StdBytesIterator> {
let range = self.parse_range(range)?;
Ok(StdBytesIterator::new(self.ctx, range))
}
}