From 2612b6f20fc21fb92402aa9086d13a7192ae3814 Mon Sep 17 00:00:00 2001
From: Divy Srivastava <dj.srivastava23@gmail.com>
Date: Wed, 20 Apr 2022 22:09:13 +0530
Subject: core: introduce `resource.read_return` (#14331)

---
 runtime/ops/io.rs | 32 +++++++++++++++++++++-----------
 1 file changed, 21 insertions(+), 11 deletions(-)

(limited to 'runtime')

diff --git a/runtime/ops/io.rs b/runtime/ops/io.rs
index 6db5d69a9..b8449af86 100644
--- a/runtime/ops/io.rs
+++ b/runtime/ops/io.rs
@@ -170,13 +170,13 @@ where
   async fn read(
     self: Rc<Self>,
     mut buf: ZeroCopyBuf,
-  ) -> Result<usize, AnyError> {
+  ) -> Result<(usize, ZeroCopyBuf), AnyError> {
     let mut rd = self.borrow_mut().await;
     let nread = rd
       .read(&mut buf)
       .try_or_cancel(self.cancel_handle())
       .await?;
-    Ok(nread)
+    Ok((nread, buf))
   }
 }
 
@@ -203,7 +203,10 @@ impl Resource for ChildStdoutResource {
     "childStdout".into()
   }
 
-  fn read(self: Rc<Self>, buf: ZeroCopyBuf) -> AsyncResult<usize> {
+  fn read_return(
+    self: Rc<Self>,
+    buf: ZeroCopyBuf,
+  ) -> AsyncResult<(usize, ZeroCopyBuf)> {
     Box::pin(self.read(buf))
   }
 
@@ -219,7 +222,10 @@ impl Resource for ChildStderrResource {
     "childStderr".into()
   }
 
-  fn read(self: Rc<Self>, buf: ZeroCopyBuf) -> AsyncResult<usize> {
+  fn read_return(
+    self: Rc<Self>,
+    buf: ZeroCopyBuf,
+  ) -> AsyncResult<(usize, ZeroCopyBuf)> {
     Box::pin(self.read(buf))
   }
 
@@ -263,16 +269,17 @@ impl StdFileResource {
   async fn read(
     self: Rc<Self>,
     mut buf: ZeroCopyBuf,
-  ) -> Result<usize, AnyError> {
+  ) -> Result<(usize, ZeroCopyBuf), AnyError> {
     if self.fs_file.is_some() {
       let fs_file = self.fs_file.as_ref().unwrap();
       let std_file = fs_file.0.as_ref().unwrap().clone();
-      tokio::task::spawn_blocking(move || {
-        let mut std_file = std_file.lock().unwrap();
-        std_file.read(&mut buf)
-      })
+      tokio::task::spawn_blocking(
+        move || -> Result<(usize, ZeroCopyBuf), AnyError> {
+          let mut std_file = std_file.lock().unwrap();
+          Ok((std_file.read(&mut buf)?, buf))
+        },
+      )
       .await?
-      .map_err(AnyError::from)
     } else {
       Err(resource_unavailable())
     }
@@ -322,7 +329,10 @@ impl Resource for StdFileResource {
     self.name.as_str().into()
   }
 
-  fn read(self: Rc<Self>, buf: ZeroCopyBuf) -> AsyncResult<usize> {
+  fn read_return(
+    self: Rc<Self>,
+    buf: ZeroCopyBuf,
+  ) -> AsyncResult<(usize, ZeroCopyBuf)> {
     Box::pin(self.read(buf))
   }
 
-- 
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