[android_webview] Don't block the IO thread when reading from an InputStream.

android_webview/browser/net/input_stream_reader.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.
+
+#ifndef ANDROID_WEBVIEW_NATIVE_INPUT_STREAM_READER_H_
+#define ANDROID_WEBVIEW_NATIVE_INPUT_STREAM_READER_H_
+
+#include "base/android/jni_android.h"
+#include "base/memory/ref_counted.h"
+
+namespace net {
+class HttpByteRange;
+class IOBuffer;
+}
+
+namespace android_webview {
+
+class InputStream;
+
+// Class responsible for reading the InputStream.
+class InputStreamReader
+    : public base::RefCountedThreadSafe<InputStreamReader> {
+ public:
+  // The constructor is called on the IO thread, not on the WorkerThread.
+  InputStreamReader(android_webview::InputStream* stream);
+
+  // Perform a seek operation on the InputStream associated with this job.
+  // On successful completion the InputStream would have skipped reading the
+  // number of bytes equal to the lower range of |byte_range|.
+  // This method should be called on the |g_worker_thread| thread.
+  //
+  // |byte_range| is the range of bytes to be read from |stream|
+  //
+  // A negative return value will indicate an error code, a positive value
+  // will indicate the expected size of the content.
+  virtual int Seek(net::HttpByteRange byte_range);
+
+  // Read data from |stream_|.  This method should be called on the
+  // |g_worker_thread| thread.
+  //
+  // A negative return value will indicate an error code, a positive value
+  // will indicate the expected size of the content.
+  virtual int ReadRawData(net::IOBuffer* buffer, int buffer_size);
+
+ protected:
+  virtual ~InputStreamReader();
+
+ private:
+  friend class base::RefCountedThreadSafe<InputStreamReader>;
+
+  // Verify the requested range against the stream size.
+  // net::OK is returned on success, the error code otherwise.
+  int VerifyRequestedRange(JNIEnv* env,
+                           net::HttpByteRange* byte_range,
+                           int* content_size);
+
+  // Skip to the first byte of the requested read range.
+  // net::OK is returned on success, the error code otherwise.
+  int SkipToRequestedRange(JNIEnv* env, const net::HttpByteRange& byte_range);
+
+  android_webview::InputStream* stream_;
+
+  DISALLOW_COPY_AND_ASSIGN(InputStreamReader);
+};
+
+} // namespace android_webview
+
+#endif //  ANDROID_WEBVIEW_NATIVE_INPUT_STREAM_READER_H_