perf(fs): improve `FileHandle.read` performance (#1950)

* perf(fs): improve `FileHandle.read` performance

* handle different target pointer width

* improve `writeTextFile` performance

* revert packageManager field

* change file

---------

Co-authored-by: Lucas Nogueira <lucas@tauri.app>

.changes/fs-perf.md

@@ -0,0 +1,6 @@
+---
+"fs": patch
+"fs-js": patch
+---
+
+Improve performance of the `FileHandle.read` and `writeTextFile` APIs.

plugins/fs/guest-js/index.ts

@@ -243,6 +243,25 @@ function parseFileInfo(r: UnparsedFileInfo): FileInfo {
   }
 }
 
+// https://mstn.github.io/2018/06/08/fixed-size-arrays-in-typescript/
+type FixedSizeArray<T, N extends number> = ReadonlyArray<T> & {
+  length: N
+}
+
+// https://gist.github.com/zapthedingbat/38ebfbedd98396624e5b5f2ff462611d
+/** Converts a big-endian eight byte array to number  */
+function fromBytes(buffer: FixedSizeArray<number, 8>): number {
+  const bytes = new Uint8ClampedArray(buffer)
+  const size = bytes.byteLength
+  let x = 0
+  for (let i = 0; i < size; i++) {
+    const byte = bytes[i]
+    x *= 0x100
+    x += byte
+  }
+  return x
+}
+
 /**
  *  The Tauri abstraction for reading and writing files.
  *
@@ -285,12 +304,20 @@ class FileHandle extends Resource {
       return 0
     }
 
-    const [data, nread] = await invoke<[number[], number]>('plugin:fs|read', {
+    const data = await invoke<ArrayBuffer | number[]>('plugin:fs|read', {
       rid: this.rid,
       len: buffer.byteLength
     })
 
-    buffer.set(data)
+    // Rust side will never return an empty array for this command and
+    // ensure there is at least 8 elements there.
+    //
+    // This is an optimization to include the number of read bytes (as bigendian bytes)
+    // at the end of returned array to avoid serialization overhead of separate values.
+    const nread = fromBytes(data.slice(-8) as FixedSizeArray<number, 8>)
+
+    const bytes = data instanceof ArrayBuffer ? new Uint8Array(data) : data
+    buffer.set(bytes.slice(0, bytes.length - 8))
 
     return nread === 0 ? null : nread
   }
@@ -1041,10 +1068,13 @@ async function writeTextFile(
     throw new TypeError('Must be a file URL.')
   }
 
-  await invoke('plugin:fs|write_text_file', {
-    path: path instanceof URL ? path.toString() : path,
-    data,
-    options
+  const encoder = new TextEncoder()
+
+  await invoke('plugin:fs|write_text_file', encoder.encode(data), {
+    headers: {
+      path: path instanceof URL ? path.toString() : path,
+      options: JSON.stringify(options)
+    }
   })
 }
 

plugins/fs/src/commands.rs

@@ -9,7 +9,7 @@ use tauri::{
     ipc::{CommandScope, GlobalScope},
     path::BaseDirectory,
     utils::config::FsScope,
-    AppHandle, Manager, Resource, ResourceId, Runtime, Webview,
+    Manager, Resource, ResourceId, Runtime, Webview,
 };
 
 use std::{
@@ -301,13 +301,34 @@ pub async fn read_dir<R: Runtime>(
 pub async fn read<R: Runtime>(
     webview: Webview<R>,
     rid: ResourceId,
-    len: u32,
-) -> CommandResult<(Vec<u8>, usize)> {
-    let mut data = vec![0; len as usize];
+    len: usize,
+) -> CommandResult<tauri::ipc::Response> {
+    let mut data = vec![0; len];
     let file = webview.resources_table().get::<StdFileResource>(rid)?;
     let nread = StdFileResource::with_lock(&file, |mut file| file.read(&mut data))
         .map_err(|e| format!("faied to read bytes from file with error: {e}"))?;
-    Ok((data, nread))
+
+    // This is an optimization to include the number of read bytes (as bigendian bytes)
+    // at the end of returned vector so we can use `tauri::ipc::Response`
+    // and avoid serialization overhead of separate values.
+    #[cfg(target_pointer_width = "16")]
+    let nread = {
+        let nread = nread.to_be_bytes();
+        let mut out = [0; 8];
+        out[6..].copy_from_slice(&nread);
+    };
+    #[cfg(target_pointer_width = "32")]
+    let nread = {
+        let nread = nread.to_be_bytes();
+        let mut out = [0; 8];
+        out[4..].copy_from_slice(&nread);
+    };
+    #[cfg(target_pointer_width = "64")]
+    let nread = nread.to_be_bytes();
+
+    data.extend(nread);
+
+    Ok(tauri::ipc::Response::new(data))
 }
 
 #[tauri::command]
@@ -783,10 +804,34 @@ fn write_file_inner<R: Runtime>(
     webview: Webview<R>,
     global_scope: &GlobalScope<Entry>,
     command_scope: &CommandScope<Entry>,
-    path: SafeFilePath,
-    data: &[u8],
-    options: Option<WriteFileOptions>,
+    request: tauri::ipc::Request<'_>,
 ) -> CommandResult<()> {
+    let data = match request.body() {
+        tauri::ipc::InvokeBody::Raw(data) => Cow::Borrowed(data),
+        tauri::ipc::InvokeBody::Json(serde_json::Value::Array(data)) => Cow::Owned(
+            data.iter()
+                .flat_map(|v| v.as_number().and_then(|v| v.as_u64().map(|v| v as u8)))
+                .collect(),
+        ),
+        _ => return Err(anyhow::anyhow!("unexpected invoke body").into()),
+    };
+
+    let path = request
+        .headers()
+        .get("path")
+        .ok_or_else(|| anyhow::anyhow!("missing file path").into())
+        .and_then(|p| {
+            percent_encoding::percent_decode(p.as_ref())
+                .decode_utf8()
+                .map_err(|_| anyhow::anyhow!("path is not a valid UTF-8").into())
+        })
+        .and_then(|p| SafeFilePath::from_str(&p).map_err(CommandError::from))?;
+    let options: Option<WriteFileOptions> = request
+        .headers()
+        .get("options")
+        .and_then(|p| p.to_str().ok())
+        .and_then(|opts| serde_json::from_str(opts).ok());
+
     let (mut file, path) = resolve_file(
         &webview,
         global_scope,
@@ -823,7 +868,7 @@ fn write_file_inner<R: Runtime>(
         },
     )?;
 
-    file.write_all(data)
+    file.write_all(&data)
         .map_err(|e| {
             format!(
                 "failed to write bytes to file at path: {} with error: {e}",
@@ -840,52 +885,18 @@ pub async fn write_file<R: Runtime>(
     command_scope: CommandScope<Entry>,
     request: tauri::ipc::Request<'_>,
 ) -> CommandResult<()> {
-    let data = match request.body() {
-        tauri::ipc::InvokeBody::Raw(data) => Cow::Borrowed(data),
-        tauri::ipc::InvokeBody::Json(serde_json::Value::Array(data)) => Cow::Owned(
-            data.iter()
-                .flat_map(|v| v.as_number().and_then(|v| v.as_u64().map(|v| v as u8)))
-                .collect(),
-        ),
-        _ => return Err(anyhow::anyhow!("unexpected invoke body").into()),
-    };
-
-    let path = request
-        .headers()
-        .get("path")
-        .ok_or_else(|| anyhow::anyhow!("missing file path").into())
-        .and_then(|p| {
-            percent_encoding::percent_decode(p.as_ref())
-                .decode_utf8()
-                .map_err(|_| anyhow::anyhow!("path is not a valid UTF-8").into())
-        })
-        .and_then(|p| SafeFilePath::from_str(&p).map_err(CommandError::from))?;
-    let options = request
-        .headers()
-        .get("options")
-        .and_then(|p| p.to_str().ok())
-        .and_then(|opts| serde_json::from_str(opts).ok());
-    write_file_inner(webview, &global_scope, &command_scope, path, &data, options)
+    write_file_inner(webview, &global_scope, &command_scope, request)
 }
 
+// TODO, in v3, remove this command and rely on `write_file` command only
 #[tauri::command]
 pub async fn write_text_file<R: Runtime>(
-    #[allow(unused)] app: AppHandle<R>,
-    #[allow(unused)] webview: Webview<R>,
-    #[allow(unused)] global_scope: GlobalScope<Entry>,
-    #[allow(unused)] command_scope: CommandScope<Entry>,
-    path: SafeFilePath,
-    data: String,
-    #[allow(unused)] options: Option<WriteFileOptions>,
+    webview: Webview<R>,
+    global_scope: GlobalScope<Entry>,
+    command_scope: CommandScope<Entry>,
+    request: tauri::ipc::Request<'_>,
 ) -> CommandResult<()> {
-    write_file_inner(
-        webview,
-        &global_scope,
-        &command_scope,
-        path,
-        data.as_bytes(),
-        options,
-    )
+    write_file_inner(webview, &global_scope, &command_scope, request)
 }
 
 #[tauri::command]