net: FileStream cleanup

net/base/file_stream.h

 // 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.
 
 // This file defines FileStream, a basic interface for reading and writing files
 // synchronously or asynchronously with support for seeking to an offset.
 // Note that even when used asynchronously, only one operation is supported at
 // a time.
 
 #ifndef NET_BASE_FILE_STREAM_H_
 #define NET_BASE_FILE_STREAM_H_
 
 #include "base/files/file.h"
 #include "net/base/completion_callback.h"
-#include "net/base/file_stream_whence.h"
 #include "net/base/net_export.h"
 
 namespace base {
 class FilePath;
 class TaskRunner;
 }
 
 namespace net {
 
 class IOBuffer;
@@ skipping 36 matching lines @@
 
   // Returns true if Open succeeded and Close has not been called.
   virtual bool IsOpen() const;
 
   // Adjust the position from where data is read asynchronously.
   // Upon success, ERR_IO_PENDING is returned and |callback| will be run
   // on the thread where Seek() was called with the the stream position
   // relative to the start of the file.  Otherwise, an error code is returned.
   // It is invalid to request any asynchronous operations while there is an
   // in-flight asynchronous operation.
-  virtual int Seek(Whence whence, int64 offset,
+  virtual int Seek(base::File::Whence whence, int64 offset,
                    const Int64CompletionCallback& callback);
 
   // Call this method to read data from the current stream position
   // asynchronously. Up to buf_len bytes will be copied into buf.  (In
   // other words, partial reads are allowed.)  Returns the number of bytes
   // copied, 0 if at end-of-file, or an error code if the operation could
   // not be performed.
   //
   // The file must be opened with FLAG_ASYNC, and a non-null
   // callback must be passed to this method. If the read could not
   // complete synchronously, then ERR_IO_PENDING is returned, and the
   // callback will be run on the thread where Read() was called, when the
   // read has completed.
   //
   // It is valid to destroy or close the file stream while there is an
   // asynchronous read in progress.  That will cancel the read and allow
   // the buffer to be freed.
   //
   // It is invalid to request any asynchronous operations while there is an
   // in-flight asynchronous operation.
   //
   // This method must not be called if the stream was opened WRITE_ONLY.
   virtual int Read(IOBuffer* buf, int buf_len,
                    const CompletionCallback& callback);
 
+  // Same as Read, but delays starting the operation until it should complete
+  // without blocking, reducing the load on the task_runner. It is the caller's
+  // responsibility to determine if using non-blocking IO is appropriate or not.
+  // For example, using this with regular files will most likely hang on POSIX.
+  // This method does the same as Read on Windows, as Read uses async IO instead
+  // of blocking IO.
+  virtual int ReadNonBlocking(IOBuffer* buf, int buf_len,
+                              const CompletionCallback& callback);
+
   // Call this method to write data at the current stream position
   // asynchronously.  Up to buf_len bytes will be written from buf. (In
   // other words, partial writes are allowed.)  Returns the number of
   // bytes written, or an error code if the operation could not be
   // performed.
   //
   // The file must be opened with FLAG_ASYNC, and a non-null
   // callback must be passed to this method. If the write could not
   // complete synchronously, then ERR_IO_PENDING is returned, and the
   // callback will be run on the thread where Write() was called when
   // the write has completed.
   //
   // It is valid to destroy or close the file stream while there is an
   // asynchronous write in progress.  That will cancel the write and allow
   // the buffer to be freed.
   //
   // It is invalid to request any asynchronous operations while there is an
   // in-flight asynchronous operation.
   //
   // This method must not be called if the stream was opened READ_ONLY.
   //
   // Zero byte writes are not allowed.
   virtual int Write(IOBuffer* buf, int buf_len,
                     const CompletionCallback& callback);
 
+  // Same as Write, but delays starting the operation until it should complete
+  // without blocking, reducing the load on the task_runner. It is the caller's
+  // responsibility to determine if using non-blocking IO is appropriate or not.
+  // For example, using this with regular files will most likely hang on POSIX.
+  // This method does the same as Write on Windows, as Write uses async IO
+  // instead of blocking IO.
+  virtual int WriteNonBlocking(IOBuffer* buf, int buf_len,
+                               const CompletionCallback& callback);
+
   // Forces out a filesystem sync on this file to make sure that the file was
   // written out to disk and is not currently sitting in the buffer. This does
   // not have to be called, it just forces one to happen at the time of
   // calling.
   //
   // The file must be opened with FLAG_ASYNC, and a non-null
   // callback must be passed to this method. If the write could not
   // complete synchronously, then ERR_IO_PENDING is returned, and the
   // callback will be run on the thread where Flush() was called when
   // the write has completed.
@@ skipping 20 matching lines @@
   // without explicitly calling Close, the file should be closed asynchronously
   // without delaying FileStream's destructor.
   scoped_ptr<Context> context_;
 
   DISALLOW_COPY_AND_ASSIGN(FileStream);
 };
 
 }  // namespace net
 
 #endif  // NET_BASE_FILE_STREAM_H_