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

android_webview/browser/net/input_stream_reader.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 "android_webview/browser/net/input_stream_reader.h"
+
+#include "android_webview/browser/input_stream.h"
+#include "base/message_loop.h"
+#include "content/public/browser/browser_thread.h"
+#include "net/base/net_errors.h"
+#include "net/http/http_byte_range.h"
+
+using content::BrowserThread;
+
+namespace android_webview {
+
+InputStreamReader::InputStreamReader(android_webview::InputStream* stream)
+    : stream_(stream) {
+  DCHECK(stream);
+}
+
+InputStreamReader::~InputStreamReader() {
+}
+
+int InputStreamReader::Seek(const net::HttpByteRange& byte_range) {
+  int content_size = 0;
+  net::HttpByteRange verified_byte_range(byte_range);
+
+  int error_code = VerifyRequestedRange(&verified_byte_range, &content_size);
+  if (error_code != net::OK)
+    return error_code;
+
+  error_code = SkipToRequestedRange(verified_byte_range);
+  if (error_code != net::OK)
+    return error_code;
+
+  DCHECK_GE(content_size, 0);
+  return content_size;
+}
+
+int InputStreamReader::ReadRawData(net::IOBuffer* dest, int dest_size) {
+  if (!dest_size)
+    return 0;
+
+  DCHECK_GT(dest_size, 0);
+
+  int bytes_read = 0;
+  if (!stream_->Read(dest, dest_size, &bytes_read))
+    return net::ERR_FAILED;
+  else
+    return bytes_read;
+}
+
+int InputStreamReader::VerifyRequestedRange(net::HttpByteRange* byte_range,
+                                            int* content_size) {
+  DCHECK(content_size);
+  int32_t size = 0;
+  if (!stream_->BytesAvailable(&size))
+    return net::ERR_FAILED;
+
+  if (size <= 0)
+    return net::OK;
+
+  // Check that the requested range was valid.
+  if (!byte_range->ComputeBounds(size))
+    return net::ERR_REQUEST_RANGE_NOT_SATISFIABLE;
+
+  size = byte_range->last_byte_position() -
+         byte_range->first_byte_position() + 1;
+  DCHECK_GE(size, 0);
+  *content_size = size;
+
+  return net::OK;
+}
+
+int InputStreamReader::SkipToRequestedRange(
+    const net::HttpByteRange& byte_range) {
+  // Skip to the start of the requested data. This has to be done in a loop
+  // because the underlying InputStream is not guaranteed to skip the requested
+  // number of bytes.
+  if (byte_range.IsValid() && byte_range.first_byte_position() > 0) {
+    int64_t bytes_to_skip = byte_range.first_byte_position();
+    do {
+      int64_t skipped = 0;
+      if (!stream_->Skip(bytes_to_skip, &skipped))
+        return net::ERR_FAILED;
+
+      if (skipped <= 0)
+        return net::ERR_REQUEST_RANGE_NOT_SATISFIABLE;
+      DCHECK(skipped <= bytes_to_skip);
+
+      bytes_to_skip -= skipped;
+    } while (bytes_to_skip > 0);
+  }
+  return net::OK;
+}
+
+} // namespace android_webview