From 7a802726fb1cf1ec8487a4af1868b7d065163f08 Mon Sep 17 00:00:00 2001
From: ClSlaid <cailue@bupt.edu.cn>
Date: Sat, 28 Oct 2023 20:52:08 +0800
Subject: [PATCH] fix: implement lazy reading to prevent avoid fd limit

drawback: through put reduced to 50%

Signed-off-by: ClSlaid <cailue@bupt.edu.cn>
---
 .../src/platform/linux/local_file.rs          | 48 ++++++++++++++-----
 libs/clipboard/src/platform/linux/mod.rs      | 28 ++---------
 2 files changed, 40 insertions(+), 36 deletions(-)

diff --git a/libs/clipboard/src/platform/linux/local_file.rs b/libs/clipboard/src/platform/linux/local_file.rs
index f49274b7a99a..c585758dfbec 100644
--- a/libs/clipboard/src/platform/linux/local_file.rs
+++ b/libs/clipboard/src/platform/linux/local_file.rs
@@ -1,5 +1,9 @@
 use std::{
-    collections::HashSet, fs::File, os::unix::prelude::PermissionsExt, path::PathBuf,
+    collections::HashSet,
+    fs::File,
+    io::{Read, Seek},
+    os::unix::prelude::PermissionsExt,
+    path::PathBuf,
     time::SystemTime,
 };
 
@@ -63,16 +67,8 @@ impl LocalFile {
             .trim_start_matches('/')
             .replace('/', "\\");
 
-        let handle = if is_dir {
-            None
-        } else {
-            let file = std::fs::File::open(path).map_err(|e| CliprdrError::FileError {
-                path: path.clone(),
-                err: e,
-            })?;
-            let reader = file;
-            Some(reader)
-        };
+        // NOTE: open files lazily
+        let handle = None;
 
         Ok(Self {
             name,
@@ -163,6 +159,36 @@ impl LocalFile {
 
         buf.to_vec()
     }
+
+    pub fn read_exact_at(&mut self, buf: &mut [u8], offset: u64) -> Result<(), CliprdrError> {
+        if self.handle.is_none() {
+            let handle = std::fs::File::open(&self.path).map_err(|e| CliprdrError::FileError {
+                path: self.path.clone(),
+                err: e,
+            })?;
+            self.handle = Some(handle);
+        };
+
+        let handle = self.handle.as_mut().unwrap();
+
+        handle
+            .seek(std::io::SeekFrom::Start(offset))
+            .map_err(|e| CliprdrError::FileError {
+                path: self.path.clone(),
+                err: e,
+            })?;
+        handle
+            .read_exact(buf)
+            .map_err(|e| CliprdrError::FileError {
+                path: self.path.clone(),
+                err: e,
+            })?;
+        // gc
+        if offset + (buf.len() as u64) >= self.size {
+            self.handle = None;
+        }
+        Ok(())
+    }
 }
 
 pub(super) fn construct_file_list(paths: &[PathBuf]) -> Result<Vec<LocalFile>, CliprdrError> {
diff --git a/libs/clipboard/src/platform/linux/mod.rs b/libs/clipboard/src/platform/linux/mod.rs
index 14ae0a164924..f1f429946e53 100644
--- a/libs/clipboard/src/platform/linux/mod.rs
+++ b/libs/clipboard/src/platform/linux/mod.rs
@@ -1,5 +1,4 @@
 use std::{
-    os::unix::prelude::FileExt,
     path::PathBuf,
     sync::{mpsc::Sender, Arc},
     time::Duration,
@@ -189,7 +188,7 @@ impl ClipboardContext {
         conn_id: i32,
         request: FileContentsRequest,
     ) -> Result<(), CliprdrError> {
-        let file_list = self.local_files.lock();
+        let mut file_list = self.local_files.lock();
 
         let file_contents_resp = match request {
             FileContentsRequest::Size {
@@ -239,7 +238,7 @@ impl ClipboardContext {
                     length,
                     conn_id
                 );
-                let Some(file) = file_list.get(file_idx) else {
+                let Some(file) = file_list.get_mut(file_idx) else {
                     log::error!(
                         "invalid file index {} requested from conn: {}",
                         file_idx,
@@ -260,22 +259,6 @@ impl ClipboardContext {
                     file.name
                 );
 
-                let Some(handle) = &file.handle else {
-                    log::error!(
-                        "invalid file index {} requested from conn: {}",
-                        file_idx,
-                        conn_id
-                    );
-                    resp_file_contents_fail(conn_id, stream_id);
-
-                    return Err(CliprdrError::InvalidRequest {
-                        description: format!(
-                            "request to read directory on index {} as file from conn: {}",
-                            file_idx, conn_id
-                        ),
-                    });
-                };
-
                 if offset > file.size {
                     log::error!("invalid reading offset requested from conn: {}", conn_id);
                     resp_file_contents_fail(conn_id, stream_id);
@@ -295,12 +278,7 @@ impl ClipboardContext {
 
                 let mut buf = vec![0u8; read_size as usize];
 
-                handle
-                    .read_exact_at(&mut buf, offset)
-                    .map_err(|e| CliprdrError::FileError {
-                        path: file.path.clone(),
-                        err: e,
-                    })?;
+                file.read_exact_at(&mut buf, offset)?;
 
                 ClipboardFile::FileContentsResponse {
                     msg_flags: 0x1,