The ReadFile API on Windows invoked by the FileStream::Context class which is used by URLRequestFil…

net/base/file_stream_context_win.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/base/file_stream_context.h"
 
 #include <windows.h>
 
 #include "base/files/file_path.h"
 #include "base/logging.h"
+#include "base/message_loop/message_loop.h"
+#include "base/message_loop/message_loop_proxy.h"
 #include "base/metrics/histogram.h"
 #include "base/profiler/scoped_tracker.h"
 #include "base/task_runner.h"
+#include "base/threading/worker_pool.h"
 #include "net/base/io_buffer.h"
 #include "net/base/net_errors.h"
 
 namespace net {
 
 namespace {
 
 void SetOffset(OVERLAPPED* overlapped, const LARGE_INTEGER& offset) {
   overlapped->Offset = offset.LowPart;
   overlapped->OffsetHigh = offset.HighPart;
 }
 
 void IncrementOffset(OVERLAPPED* overlapped, DWORD count) {
   LARGE_INTEGER offset;
   offset.LowPart = overlapped->Offset;
   offset.HighPart = overlapped->OffsetHigh;
   offset.QuadPart += static_cast<LONGLONG>(count);
   SetOffset(overlapped, offset);
 }
 
 }  // namespace
 
 FileStream::Context::Context(const scoped_refptr<base::TaskRunner>& task_runner)
     : io_context_(),
       async_in_progress_(false),
       orphaned_(false),
-      task_runner_(task_runner) {
+      task_runner_(task_runner),
+      weak_ptr_factory_(this) {
   io_context_.handler = this;
   memset(&io_context_.overlapped, 0, sizeof(io_context_.overlapped));
 }
 
 FileStream::Context::Context(base::File file,
                              const scoped_refptr<base::TaskRunner>& task_runner)
     : io_context_(),
       file_(file.Pass()),
       async_in_progress_(false),
       orphaned_(false),
-      task_runner_(task_runner) {
+      task_runner_(task_runner),
+      weak_ptr_factory_(this) {
   io_context_.handler = this;
   memset(&io_context_.overlapped, 0, sizeof(io_context_.overlapped));
   if (file_.IsValid()) {
     // TODO(hashimoto): Check that file_ is async.
     OnFileOpened();
   }
 }
 
 FileStream::Context::~Context() {
 }
 
 int FileStream::Context::Read(IOBuffer* buf,
                               int buf_len,
                               const CompletionCallback& callback) {
   // TODO(vadimt): Remove ScopedTracker below once crbug.com/423948 is fixed.
   tracked_objects::ScopedTracker tracking_profile(
       FROM_HERE_WITH_EXPLICIT_FUNCTION("423948 FileStream::Context::Read"));
 
   DCHECK(!async_in_progress_);
 
-  DWORD bytes_read;
-  if (!ReadFile(file_.GetPlatformFile(), buf->data(), buf_len,
-                &bytes_read, &io_context_.overlapped)) {
-    IOResult error = IOResult::FromOSError(GetLastError());
-    if (error.os_error == ERROR_HANDLE_EOF)
-      return 0;  // Report EOF by returning 0 bytes read.
-    if (error.os_error == ERROR_IO_PENDING)
-      IOCompletionIsPending(callback, buf);
-    else
-      LOG(WARNING) << "ReadFile failed: " << error.os_error;
-    return static_cast<int>(error.result);
-  }
+  IOCompletionIsPending(callback, buf);
 
-  IOCompletionIsPending(callback, buf);
+  base::WorkerPool::PostTask(
+      FROM_HERE,
+      base::Bind(&FileStream::Context::ReadAsync,
+                 weak_ptr_factory_.GetWeakPtr(), file_.GetPlatformFile(),
+                 make_scoped_refptr(buf), buf_len, &io_context_.overlapped,
+                 base::MessageLoop::current()->message_loop_proxy()),
+      false);
+
   return ERR_IO_PENDING;
 }
 
 int FileStream::Context::Write(IOBuffer* buf,
                                int buf_len,
                                const CompletionCallback& callback) {
   DWORD bytes_written = 0;
   if (!WriteFile(file_.GetPlatformFile(), buf->data(), buf_len,
                  &bytes_written, &io_context_.overlapped)) {
     IOResult error = IOResult::FromOSError(GetLastError());
@@ skipping 62 matching lines @@
     IncrementOffset(&io_context_.overlapped, bytes_read);
   }
 
   CompletionCallback temp_callback = callback_;
   callback_.Reset();
   scoped_refptr<IOBuffer> temp_buf = in_flight_buf_;
   in_flight_buf_ = NULL;
   temp_callback.Run(result);
 }
 
+// static
+void FileStream::Context::ReadAsync(
+    const base::WeakPtr<FileStream::Context>& context,
+    HANDLE file,
+    scoped_refptr<net::IOBuffer> buf,
+    int buf_len,
+    OVERLAPPED* overlapped,
+    scoped_refptr<base::MessageLoopProxy> origin_thread_loop) {
+  DWORD bytes_read = 0;
+  ReadFile(file, buf->data(), buf_len, &bytes_read, overlapped);
+
+  origin_thread_loop->PostTask(
+      FROM_HERE, base::Bind(&FileStream::Context::ReadAsyncResult, context,
+                            ::GetLastError()));
+}
+
+void FileStream::Context::ReadAsyncResult(DWORD os_error) {
+  IOResult error = IOResult::FromOSError(os_error);
+  if (error.os_error == ERROR_HANDLE_EOF) {
+    // Report EOF by returning 0 bytes read.
+    OnIOCompleted(&io_context_, 0, error.os_error);
+    return;

[ramant (doing other things), 2015/01/31 05:23:22]

nit: return is not needed. Or "} else if" ->
"}
 if .....
" 

[ananta, 2015/02/03 00:33:43]

Done.

+  } else if (error.os_error != ERROR_IO_PENDING) {
+    // We don't need to inform the caller about ERROR_PENDING_IO as that was
+    // already done when the ReadFile call was queued to the worker pool.
+    if (error.os_error)
+      LOG(WARNING) << "ReadFile failed: " << error.os_error;
+    OnIOCompleted(&io_context_, 0, error.os_error);
+  }
+}
+
 }  // namespace net