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From: Dominik Csapak <d.csapak@proxmox.com>
To: pbs-devel@lists.proxmox.com
Date: Mon, 14 Dec 2020 14:41:46 +0100
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Subject: [pbs-devel] [PATCH proxmox 1/1] proxmox: add sparse_copy(_async) to
tools::io
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this is able to seek the target instead of writing zeroes, which
generates sparse files where supported
Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
---
changes from RFC:
* use minimal buffer_is_zero version that generates fast code on release
compilation
proxmox/src/tools/io/mod.rs | 70 +++++++++++++++++++++++++++++++++++++
1 file changed, 70 insertions(+)
diff --git a/proxmox/src/tools/io/mod.rs b/proxmox/src/tools/io/mod.rs
index 2e92ebb..299d19c 100644
--- a/proxmox/src/tools/io/mod.rs
+++ b/proxmox/src/tools/io/mod.rs
@@ -3,8 +3,78 @@
//! The [`ReadExt`] trait provides additional operations for handling byte buffers for types
//! implementing [`Read`](std::io::Read).
+use std::io::{self, Read, Write, Seek, SeekFrom, ErrorKind};
+
mod read;
pub use read::*;
mod write;
pub use write::*;
+
+fn buffer_is_zero(buf: &[u8]) -> bool {
+ !buf
+ .chunks(128)
+ .map(|aa|
+ aa.iter().fold(0, |a, b| a|b) != 0
+ ).any(|a| a)
+}
+
+/// copy similar to io::copy, but seeks the target when encountering
+/// zero bytes instead of writing them
+pub fn sparse_copy<R: Read + ?Sized, W: Write + Seek + ?Sized>(
+ reader: &mut R,
+ writer: &mut W,
+) -> Result<u64, io::Error> {
+ let mut buf = crate::tools::byte_buffer::ByteBuffer::new();
+ let mut written = 0;
+ loop {
+ let len = match buf.read_from(reader) {
+ Ok(0) => return Ok(written),
+ Ok(len) => len,
+ Err(ref e) if e.kind() == ErrorKind::Interrupted => continue,
+ Err(e) => return Err(e),
+ };
+
+ if buffer_is_zero(&buf[..]) {
+ writer.seek(SeekFrom::Current(len as i64))?;
+ } else {
+ writer.write_all(&buf[..])?;
+ }
+ buf.clear();
+ written += len as u64;
+ }
+}
+
+#[cfg(feature = "tokio")]
+use tokio::io::{AsyncReadExt, AsyncWriteExt, AsyncSeekExt};
+
+#[cfg(feature = "tokio")]
+/// copy similar to tokio::io::copy, but seeks the target when encountering
+/// zero bytes instead of writing them
+pub async fn sparse_copy_async<R, W>(
+ reader: &mut R,
+ writer: &mut W,
+) -> Result<u64, io::Error>
+where
+ R: AsyncReadExt + Unpin,
+ W: AsyncWriteExt + AsyncSeekExt + Unpin,
+{
+ let mut buf = crate::tools::byte_buffer::ByteBuffer::new();
+ let mut written = 0;
+ loop {
+ let len = match buf.read_from_async(reader).await {
+ Ok(0) => return Ok(written),
+ Ok(len) => len,
+ Err(ref e) if e.kind() == ErrorKind::Interrupted => continue,
+ Err(e) => return Err(e),
+ };
+
+ if buffer_is_zero(&buf[..]) {
+ writer.seek(SeekFrom::Current(len as i64)).await?;
+ } else {
+ writer.write_all(&buf[..]).await?;
+ }
+ buf.clear();
+ written += len as u64;
+ }
+}
--
2.20.1