Disk Cache: Use the old WorkerPool for Async IO on iOS.

net/disk_cache/file_ios.cc

Index: net/disk_cache/file_ios.cc
diff --git a/net/disk_cache/file_posix.cc b/net/disk_cache/file_ios.cc
similarity index 35%
copy from net/disk_cache/file_posix.cc
copy to net/disk_cache/file_ios.cc
index 30c4a660b13777351dd0d1f4c6d38b6615aa01fd..b8f22fd91b14b341976ab4c5bd74b9c183636510 100644
--- a/net/disk_cache/file_posix.cc
+++ b/net/disk_cache/file_ios.cc
@@ -5,30 +5,162 @@
 #include "net/disk_cache/file.h"
 
 #include "base/bind.h"
-#include "base/lazy_instance.h"
 #include "base/location.h"
 #include "base/logging.h"
-#include "base/run_loop.h"
-#include "base/task_runner_util.h"
-#include "base/threading/sequenced_worker_pool.h"
+#include "base/threading/worker_pool.h"
 #include "net/base/net_errors.h"
 #include "net/disk_cache/disk_cache.h"
+#include "net/disk_cache/in_flight_io.h"
 
 namespace {
 
-// The maximum number of threads for this pool.
-const int kMaxThreads = 5;
+// This class represents a single asynchronous IO operation while it is being
+// bounced between threads.
+class FileBackgroundIO : public disk_cache::BackgroundIO {
+ public:
+  // Other than the actual parameters for the IO operation (including the
+  // |callback| that must be notified at the end), we need the controller that
+  // is keeping track of all operations. When done, we notify the controller
+  // (we do NOT invoke the callback), in the worker thead that completed the
+  // operation.
+  FileBackgroundIO(disk_cache::File* file, const void* buf, size_t buf_len,
+                   size_t offset, disk_cache::FileIOCallback* callback,
+                   disk_cache::InFlightIO* controller)
+      : disk_cache::BackgroundIO(controller), callback_(callback), file_(file),
+        buf_(buf), buf_len_(buf_len), offset_(offset) {
+  }
+
+  disk_cache::FileIOCallback* callback() {
+    return callback_;
+  }
+
+  disk_cache::File* file() {
+    return file_;
+  }
+
+  // Read and Write are the operations that can be performed asynchronously.
+  // The actual parameters for the operation are setup in the constructor of
+  // the object. Both methods should be called from a worker thread, by posting
+  // a task to the WorkerPool (they are RunnableMethods). When finished,
+  // controller->OnIOComplete() is called.
+  void Read();
+  void Write();
+
+ private:
+  virtual ~FileBackgroundIO() {}
 
-class FileWorkerPool : public base::SequencedWorkerPool {
+  disk_cache::FileIOCallback* callback_;
+
+  disk_cache::File* file_;
+  const void* buf_;
+  size_t buf_len_;
+  size_t offset_;
+
+  DISALLOW_COPY_AND_ASSIGN(FileBackgroundIO);
+};
+
+
+// The specialized controller that keeps track of current operations.
+class FileInFlightIO : public disk_cache::InFlightIO {
  public:
-  FileWorkerPool() : base::SequencedWorkerPool(kMaxThreads, "CachePool") {}
+  FileInFlightIO() {}
+  virtual ~FileInFlightIO() {}
+
+  // These methods start an asynchronous operation. The arguments have the same
+  // semantics of the File asynchronous operations, with the exception that the
+  // operation never finishes synchronously.
+  void PostRead(disk_cache::File* file, void* buf, size_t buf_len,
+                size_t offset, disk_cache::FileIOCallback* callback);
+  void PostWrite(disk_cache::File* file, const void* buf, size_t buf_len,
+                 size_t offset, disk_cache::FileIOCallback* callback);
 
  protected:
-  virtual ~FileWorkerPool() {}
+  // Invokes the users' completion callback at the end of the IO operation.
+  // |cancel| is true if the actual task posted to the thread is still
+  // queued (because we are inside WaitForPendingIO), and false if said task is
+  // the one performing the call.
+  virtual void OnOperationComplete(disk_cache::BackgroundIO* operation,
+                                   bool cancel) OVERRIDE;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(FileInFlightIO);
 };
 
-base::LazyInstance<FileWorkerPool>::Leaky s_worker_pool =
-    LAZY_INSTANCE_INITIALIZER;
+// ---------------------------------------------------------------------------
+
+// Runs on a worker thread.
+void FileBackgroundIO::Read() {
+  if (file_->Read(const_cast<void*>(buf_), buf_len_, offset_)) {
+    result_ = static_cast<int>(buf_len_);
+  } else {
+    result_ = net::ERR_CACHE_READ_FAILURE;
+  }
+  NotifyController();
+}
+
+// Runs on a worker thread.
+void FileBackgroundIO::Write() {
+  bool rv = file_->Write(buf_, buf_len_, offset_);
+
+  result_ = rv ? static_cast<int>(buf_len_) : net::ERR_CACHE_WRITE_FAILURE;
+  NotifyController();
+}
+
+// ---------------------------------------------------------------------------
+
+void FileInFlightIO::PostRead(disk_cache::File *file, void* buf, size_t buf_len,
+                          size_t offset, disk_cache::FileIOCallback *callback) {
+  scoped_refptr<FileBackgroundIO> operation(
+      new FileBackgroundIO(file, buf, buf_len, offset, callback, this));
+  file->AddRef();  // Balanced on OnOperationComplete()
+
+  base::WorkerPool::PostTask(FROM_HERE,
+      base::Bind(&FileBackgroundIO::Read, operation.get()), true);
+  OnOperationPosted(operation.get());
+}
+
+void FileInFlightIO::PostWrite(disk_cache::File* file, const void* buf,
+                           size_t buf_len, size_t offset,
+                           disk_cache::FileIOCallback* callback) {
+  scoped_refptr<FileBackgroundIO> operation(
+      new FileBackgroundIO(file, buf, buf_len, offset, callback, this));
+  file->AddRef();  // Balanced on OnOperationComplete()
+
+  base::WorkerPool::PostTask(FROM_HERE,
+      base::Bind(&FileBackgroundIO::Write, operation.get()), true);
+  OnOperationPosted(operation.get());
+}
+
+// Runs on the IO thread.
+void FileInFlightIO::OnOperationComplete(disk_cache::BackgroundIO* operation,
+                                         bool cancel) {
+  FileBackgroundIO* op = static_cast<FileBackgroundIO*>(operation);
+
+  disk_cache::FileIOCallback* callback = op->callback();
+  int bytes = operation->result();
+
+  // Release the references acquired in PostRead / PostWrite.
+  op->file()->Release();
+  callback->OnFileIOComplete(bytes);
+}
+
+// A static object tha will broker all async operations.
+FileInFlightIO* s_file_operations = NULL;
+
+// Returns the current FileInFlightIO.
+FileInFlightIO* GetFileInFlightIO() {
+  if (!s_file_operations) {
+    s_file_operations = new FileInFlightIO;
+  }
+  return s_file_operations;
+}
+
+// Deletes the current FileInFlightIO.
+void DeleteFileInFlightIO() {
+  DCHECK(s_file_operations);
+  delete s_file_operations;
+  s_file_operations = NULL;
+}
 
 }  // namespace
 
@@ -93,6 +225,9 @@ bool File::Write(const void* buffer, size_t buffer_len, size_t offset) {
   return (static_cast<size_t>(ret) == buffer_len);
 }
 
+// We have to increase the ref counter of the file before performing the IO to
+// prevent the completion to happen with an invalid handle (if the file is
+// closed while the IO is in flight).
 bool File::Read(void* buffer, size_t buffer_len, size_t offset,
                 FileIOCallback* callback, bool* completed) {
   DCHECK(init_);
@@ -102,15 +237,10 @@ bool File::Read(void* buffer, size_t buffer_len, size_t offset,
     return Read(buffer, buffer_len, offset);
   }
 
-  if (buffer_len > static_cast<size_t>(kint32max) ||
-      offset > static_cast<size_t>(kint32max)) {
+  if (buffer_len > ULONG_MAX || offset > ULONG_MAX)
     return false;
-  }
 
-  base::PostTaskAndReplyWithResult(
-      s_worker_pool.Pointer(), FROM_HERE,
-      base::Bind(&File::DoRead, this, buffer, buffer_len, offset),
-      base::Bind(&File::OnOperationComplete, this, callback));
+  GetFileInFlightIO()->PostRead(this, buffer, buffer_len, offset, callback);
 
   *completed = false;
   return true;
@@ -125,18 +255,7 @@ bool File::Write(const void* buffer, size_t buffer_len, size_t offset,
     return Write(buffer, buffer_len, offset);
   }
 
-  if (buffer_len > static_cast<size_t>(kint32max) ||
-      offset > static_cast<size_t>(kint32max)) {
-    return false;
-  }
-
-  base::PostTaskAndReplyWithResult(
-      s_worker_pool.Pointer(), FROM_HERE,
-      base::Bind(&File::DoWrite, this, buffer, buffer_len, offset),
-      base::Bind(&File::OnOperationComplete, this, callback));
-
-  *completed = false;
-  return true;
+  return AsyncWrite(buffer, buffer_len, offset, callback, completed);
 }
 
 bool File::SetLength(size_t length) {
@@ -160,11 +279,16 @@ size_t File::GetLength() {
 
 // Static.
 void File::WaitForPendingIO(int* num_pending_io) {
-  // We are running unit tests so we should wait for all callbacks. Sadly, the
-  // worker pool only waits for tasks on the worker pool, not the "Reply" tasks
-  // so we have to let the current message loop to run.
-  s_worker_pool.Get().FlushForTesting();
-  base::RunLoop().RunUntilIdle();
+  // We may be running unit tests so we should allow be able to reset the
+  // message loop.
+  GetFileInFlightIO()->WaitForPendingIO();
+  DeleteFileInFlightIO();
+}
+
+// Static.
+void File::DropPendingIO() {
+  GetFileInFlightIO()->DropPendingIO();
+  DeleteFileInFlightIO();
 }
 
 File::~File() {
@@ -172,26 +296,17 @@ File::~File() {
     base::ClosePlatformFile(platform_file_);
 }
 
-// Runs on a worker thread.
-int File::DoRead(void* buffer, size_t buffer_len, size_t offset) {
-  if (Read(const_cast<void*>(buffer), buffer_len, offset))
-    return static_cast<int>(buffer_len);
-
-  return net::ERR_CACHE_READ_FAILURE;
-}
-
-// Runs on a worker thread.
-int File::DoWrite(const void* buffer, size_t buffer_len, size_t offset) {
-  if (Write(const_cast<void*>(buffer), buffer_len, offset))
-    return static_cast<int>(buffer_len);
+bool File::AsyncWrite(const void* buffer, size_t buffer_len, size_t offset,
+                      FileIOCallback* callback, bool* completed) {
+  DCHECK(init_);
+  if (buffer_len > ULONG_MAX || offset > ULONG_MAX)
+    return false;
 
-  return net::ERR_CACHE_WRITE_FAILURE;
-}
+  GetFileInFlightIO()->PostWrite(this, buffer, buffer_len, offset, callback);
 
-// This method actually makes sure that the last reference to the file doesn't
-// go away on the worker pool.
-void File::OnOperationComplete(FileIOCallback* callback, int result) {
-  callback->OnFileIOComplete(result);
+  if (completed)
+    *completed = false;
+  return true;
 }
 
 }  // namespace disk_cache