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

android_webview/browser/input_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.
+
+#ifndef ANDROID_WEBVIEW_BROWSER_INPUT_STREAM_H_
+#define ANDROID_WEBVIEW_BROWSER_INPUT_STREAM_H_
+
+#include "base/android/jni_android.h"
+
+namespace net {
+class IOBuffer;
+}
+
+namespace android_webview {
+
+class InputStream {
+ public:
+  virtual ~InputStream() {}
+
+  // Sets |bytes_available| to the number of bytes that can be read (or skipped
+  // over) from this input stream without blocking by the next caller of a
+  // method for this input stream.
+  // Returns true if completed successfully or false if an exception was
+  // thrown.
+  virtual bool BytesAvailable(JNIEnv* env, int* bytes_available) const = 0;
+
+  // Skips over and discards |n| bytes of data from this input stream. Sets
+  // |bytes_skipped| to the number of of bytes skipped.
+  // Returns true if completed successfully or false if an exception was
+  // thrown.
+  virtual bool Skip(JNIEnv* env, int64_t n, int64_t* bytes_skipped) = 0;
+
+  // Reads |length| bytes into |dest|. Sets |bytes_read| to the total number of
+  // bytes read into |dest| or -1 if there is no more data because the end of
+  // the stream was reached.
+  // |dest| must be at least |length| in size.
+  // Returns true if completed successfully or false if an exception was
+  // thrown.
+  virtual bool Read(JNIEnv* env,
+                    net::IOBuffer* dest,
+                    int length,
+                    int* bytes_read) = 0;
+ protected:
+  InputStream() {}
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(InputStream);
+};
+
+} // namespace android_webview
+
+#endif //  ANDROID_WEBVIEW_BROWSER_INPUT_STREAM_H_