Signed-off-by: Filip Schauer <f.scha...@proxmox.com>
---
Introduced in v3
proxmox-io/src/lib.rs | 3 ++
proxmox-io/src/range_reader.rs | 94 ++++++++++++++++++++++++++++++++++
2 files changed, 97 insertions(+)
create mode 100644 proxmox-io/src/range_reader.rs
diff --git a/proxmox-io/src/lib.rs b/proxmox-io/src/lib.rs
index 1be005ff..a05b9232 100644
--- a/proxmox-io/src/lib.rs
+++ b/proxmox-io/src/lib.rs
@@ -6,6 +6,9 @@
#![deny(unsafe_op_in_unsafe_fn)]
#![cfg_attr(docsrs, feature(doc_cfg, doc_auto_cfg))]
+mod range_reader;
+pub use range_reader::RangeReader;
+
mod read;
pub use read::ReadExt;
diff --git a/proxmox-io/src/range_reader.rs b/proxmox-io/src/range_reader.rs
new file mode 100644
index 00000000..307bfe27
--- /dev/null
+++ b/proxmox-io/src/range_reader.rs
@@ -0,0 +1,94 @@
+use std::io::{Read, Seek, SeekFrom};
+use std::ops::Range;
+
+pub struct RangeReader<R: Read + Seek> {
+ reader: R,
+
+ /// Range inside `R`.
+ range: Range<u64>,
+
+ /// Relative position inside `range`
+ position: u64,
+
+ /// True once the initial seek has been performed
+ ready: bool,
+}
+
+impl<R: Read + Seek> RangeReader<R> {
+ pub fn new(reader: R, range: Range<u64>) -> Self {
+ Self {
+ reader,
+ range,
+ position: 0,
+ ready: false,
+ }
+ }
+
+ pub fn into_inner(self) -> R {
+ self.reader
+ }
+
+ pub fn size(&self) -> usize {
+ (self.range.end - self.range.start) as usize
+ }
+
+ pub fn remaining(&self) -> usize {
+ self.size() - self.position as usize
+ }
+}
+
+impl<R: Read + Seek> Read for RangeReader<R> {
+ fn read(&mut self, buf: &mut [u8]) -> std::io::Result<usize> {
+ let max_read = buf.len().min(self.remaining());
+ let limited_buf = &mut buf[..max_read];
+
+ if !self.ready {
+ self.reader
+ .seek(SeekFrom::Start(self.range.start + self.position))?;
+ self.ready = true;
+ }
+
+ let bytes_read = self.reader.read(limited_buf)?;
+ self.position += bytes_read.min(max_read) as u64;
+
+ Ok(bytes_read)
+ }
+}
+
+impl<R: Read + Seek> Seek for RangeReader<R> {
+ fn seek(&mut self, pos: SeekFrom) -> std::io::Result<u64> {
+ self.position = match pos {
+ SeekFrom::Start(position) => position.min(self.size() as u64),
+ SeekFrom::End(offset) => {
+ if offset > self.size() as i64 {
+ return Err(std::io::Error::new(
+ std::io::ErrorKind::InvalidInput,
+ "Tried to seek before the beginning of the file",
+ ));
+ }
+
+ (if offset <= 0 {
+ self.size()
+ } else {
+ self.size() - offset as usize
+ }) as u64
+ }
+ SeekFrom::Current(offset) => {
+ if let Some(position) =
self.position.checked_add_signed(offset) {
+ position.min(self.size() as u64)
+ } else {
+ return Err(std::io::Error::new(
+ std::io::ErrorKind::InvalidInput,
+ "Tried to seek before the beginning of the file",
+ ));
+ }
+ }
+ };
+
+ self.reader
+ .seek(SeekFrom::Start(self.range.start + self.position))?;
+ self.ready = true;
+
+ Ok(self.position)
+ }
+}
--
2.47.2
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