- Add MayBlock() method to stream classes which is used as a hint when determining the thread to access the stream from (issue #1187).

- In cases where MayBlock() returns true have CefStreamResourceReader perform the reads on the FILE thread (issue #1187).

git-svn-id: https://chromiumembedded.googlecode.com/svn/trunk@1582 5089003a-bbd8-11dd-ad1f-f1f9622dbc98

cef.gyp

@@ -399,6 +399,7 @@
         'tests/cefclient/client_app.h',
         'tests/cefclient/client_switches.cpp',
         'tests/cefclient/client_switches.h',
+        'tests/cefclient/resource_util.h',
         'tests/cefclient/res/osr_test.html',
         'tests/unittests/browser_info_map_unittest.cc',
         'tests/unittests/command_line_unittest.cc',
@@ -417,12 +418,12 @@
         'tests/unittests/request_context_unittest.cc',
         'tests/unittests/request_handler_unittest.cc',
         'tests/unittests/request_unittest.cc',
-        'tests/cefclient/resource_util.h',
         'tests/unittests/routing_test_handler.cc',
         'tests/unittests/routing_test_handler.h',
         'tests/unittests/run_all_unittests.cc',
         'tests/unittests/scheme_handler_unittest.cc',
         'tests/unittests/stream_unittest.cc',
+        'tests/unittests/stream_resource_handler_unittest.cc',
         'tests/unittests/string_unittest.cc',
         'tests/unittests/client_app_delegates.cc',
         'tests/unittests/task_unittest.cc',
@@ -920,6 +921,7 @@
         'libcef/browser/download_item_impl.h',
         'libcef/browser/download_manager_delegate.cc',
         'libcef/browser/download_manager_delegate.h',
+        'libcef/browser/file_impl.cc',
         'libcef/browser/frame_host_impl.cc',
         'libcef/browser/frame_host_impl.h',
         'libcef/browser/geolocation_impl.cc',

cef_paths.gypi

@@ -28,6 +28,7 @@
       'include/cef_download_item.h',
       'include/cef_drag_data.h',
       'include/cef_drag_handler.h',
+      'include/cef_file.h',
       'include/cef_focus_handler.h',
       'include/cef_frame.h',
       'include/cef_geolocation.h',
@@ -80,6 +81,7 @@
       'include/capi/cef_download_item_capi.h',
       'include/capi/cef_drag_data_capi.h',
       'include/capi/cef_drag_handler_capi.h',
+      'include/capi/cef_file_capi.h',
       'include/capi/cef_focus_handler_capi.h',
       'include/capi/cef_frame_capi.h',
       'include/capi/cef_geolocation_capi.h',

include/capi/cef_stream_capi.h

@@ -77,6 +77,13 @@ typedef struct _cef_read_handler_t {
   // Return non-zero if at end of file.
   ///
   int (CEF_CALLBACK *eof)(struct _cef_read_handler_t* self);
+
+  ///
+  // Return true (1) if this handler performs work like accessing the file
+  // system which may block. Used as a hint for determining the thread to access
+  // the handler from.
+  ///
+  int (CEF_CALLBACK *may_block)(struct _cef_read_handler_t* self);
 } cef_read_handler_t;
 
 
@@ -112,6 +119,13 @@ typedef struct _cef_stream_reader_t {
   // Return non-zero if at end of file.
   ///
   int (CEF_CALLBACK *eof)(struct _cef_stream_reader_t* self);
+
+  ///
+  // Returns true (1) if this reader performs work like accessing the file
+  // system which may block. Used as a hint for determining the thread to access
+  // the reader from.
+  ///
+  int (CEF_CALLBACK *may_block)(struct _cef_stream_reader_t* self);
 } cef_stream_reader_t;
 
 
@@ -166,6 +180,13 @@ typedef struct _cef_write_handler_t {
   // Flush the stream.
   ///
   int (CEF_CALLBACK *flush)(struct _cef_write_handler_t* self);
+
+  ///
+  // Return true (1) if this handler performs work like accessing the file
+  // system which may block. Used as a hint for determining the thread to access
+  // the handler from.
+  ///
+  int (CEF_CALLBACK *may_block)(struct _cef_write_handler_t* self);
 } cef_write_handler_t;
 
 
@@ -201,6 +222,13 @@ typedef struct _cef_stream_writer_t {
   // Flush the stream.
   ///
   int (CEF_CALLBACK *flush)(struct _cef_stream_writer_t* self);
+
+  ///
+  // Returns true (1) if this writer performs work like accessing the file
+  // system which may block. Used as a hint for determining the thread to access
+  // the writer from.
+  ///
+  int (CEF_CALLBACK *may_block)(struct _cef_stream_writer_t* self);
 } cef_stream_writer_t;
 
 

include/cef_stream.h

@@ -71,6 +71,14 @@ class CefReadHandler : public virtual CefBase {
   ///
   /*--cef()--*/
   virtual int Eof() =0;
+
+  ///
+  // Return true if this handler performs work like accessing the file system
+  // which may block. Used as a hint for determining the thread to access the
+  // handler from.
+  ///
+  /*--cef()--*/
+  virtual bool MayBlock() =0;
 };
 
 
@@ -123,6 +131,14 @@ class CefStreamReader : public virtual CefBase {
   ///
   /*--cef()--*/
   virtual int Eof() =0;
+
+  ///
+  // Returns true if this reader performs work like accessing the file system
+  // which may block. Used as a hint for determining the thread to access the
+  // reader from.
+  ///
+  /*--cef()--*/
+  virtual bool MayBlock() =0;
 };
 
 
@@ -158,6 +174,14 @@ class CefWriteHandler : public virtual CefBase {
   ///
   /*--cef()--*/
   virtual int Flush() =0;
+
+  ///
+  // Return true if this handler performs work like accessing the file system
+  // which may block. Used as a hint for determining the thread to access the
+  // handler from.
+  ///
+  /*--cef()--*/
+  virtual bool MayBlock() =0;
 };
 
 
@@ -205,6 +229,14 @@ class CefStreamWriter : public virtual CefBase {
   ///
   /*--cef()--*/
   virtual int Flush() =0;
+
+  ///
+  // Returns true if this writer performs work like accessing the file system
+  // which may block. Used as a hint for determining the thread to access the
+  // writer from.
+  ///
+  /*--cef()--*/
+  virtual bool MayBlock() =0;
 };
 
 #endif  // CEF_INCLUDE_CEF_STREAM_H_

include/wrapper/cef_byte_read_handler.h

@@ -60,6 +60,7 @@ class CefByteReadHandler : public CefReadHandler {
   virtual int Seek(int64 offset, int whence) OVERRIDE;
   virtual int64 Tell() OVERRIDE;
   virtual int Eof() OVERRIDE;
+  virtual bool MayBlock() OVERRIDE { return false; }
 
  private:
   const unsigned char* bytes_;

include/wrapper/cef_stream_resource_handler.h

@@ -57,11 +57,14 @@ class CefStreamResourceHandler : public CefResourceHandler {
   // Create a new object with explicit response values.
   ///
   CefStreamResourceHandler(int status_code,
+                           const CefString& status_text,
                            const CefString& mime_type,
                            CefResponse::HeaderMap header_map,
                            CefRefPtr<CefStreamReader> stream);
 
-  // CefStreamResourceHandler methods.
+  virtual ~CefStreamResourceHandler();
+
+  // CefResourceHandler methods.
   virtual bool ProcessRequest(CefRefPtr<CefRequest> request,
                               CefRefPtr<CefCallback> callback) OVERRIDE;
   virtual void GetResponseHeaders(CefRefPtr<CefResponse> response,
@@ -74,10 +77,23 @@ class CefStreamResourceHandler : public CefResourceHandler {
   virtual void Cancel() OVERRIDE;
 
  private:
-  int status_code_;
-  CefString mime_type_;
-  CefResponse::HeaderMap header_map_;
-  CefRefPtr<CefStreamReader> stream_;
+  void ReadOnFileThread(int bytes_to_read,
+                        CefRefPtr<CefCallback> callback);
+
+  const int status_code_;
+  const CefString status_text_;
+  const CefString mime_type_;
+  const CefResponse::HeaderMap header_map_;
+  const CefRefPtr<CefStreamReader> stream_;
+  bool read_on_file_thread_;
+
+  class Buffer;
+  Buffer* buffer_;
+#ifndef NDEBUG
+  // Used in debug builds to verify that |buffer_| isn't being accessed on
+  // multiple threads at the same time.
+  bool buffer_owned_by_file_thread_;
+#endif
 
   IMPLEMENT_REFCOUNTING(CefStreamResourceHandler);
 };

libcef/browser/stream_impl.h

@@ -20,6 +20,7 @@ class CefFileReader : public CefStreamReader {
   virtual int Seek(int64 offset, int whence) OVERRIDE;
   virtual int64 Tell() OVERRIDE;
   virtual int Eof() OVERRIDE;
+  virtual bool MayBlock() OVERRIDE { return true; }
 
  protected:
   bool close_;
@@ -39,6 +40,7 @@ class CefFileWriter : public CefStreamWriter {
   virtual int Seek(int64 offset, int whence) OVERRIDE;
   virtual int64 Tell() OVERRIDE;
   virtual int Flush() OVERRIDE;
+  virtual bool MayBlock() OVERRIDE { return true; }
 
  protected:
   FILE* file_;
@@ -58,6 +60,7 @@ class CefBytesReader : public CefStreamReader {
   virtual int Seek(int64 offset, int whence) OVERRIDE;
   virtual int64 Tell() OVERRIDE;
   virtual int Eof() OVERRIDE;
+  virtual bool MayBlock() OVERRIDE { return false; }
 
   void SetData(void* data, int64 datasize, bool copy);
 
@@ -84,6 +87,7 @@ class CefBytesWriter : public CefStreamWriter {
   virtual int Seek(int64 offset, int whence) OVERRIDE;
   virtual int64 Tell() OVERRIDE;
   virtual int Flush() OVERRIDE;
+  virtual bool MayBlock() OVERRIDE { return false; }
 
   void* GetData() { return data_; }
   int64 GetDataSize() { return offset_; }
@@ -119,6 +123,9 @@ class CefHandlerReader : public CefStreamReader {
   virtual int Eof() OVERRIDE {
     return handler_->Eof();
   }
+  virtual bool MayBlock() OVERRIDE {
+    return handler_->MayBlock();
+  }
 
  protected:
   CefRefPtr<CefReadHandler> handler_;
@@ -144,6 +151,9 @@ class CefHandlerWriter : public CefStreamWriter {
   virtual int Flush() OVERRIDE {
     return handler_->Flush();
   }
+  virtual bool MayBlock() OVERRIDE {
+    return handler_->MayBlock();
+  }
 
  protected:
   CefRefPtr<CefWriteHandler> handler_;

libcef_dll/cef_logging.h

@@ -28,6 +28,8 @@
 #endif  // !BUILDING_CEF_SHARED
 
 #define CEF_REQUIRE_UI_THREAD()       DCHECK(CefCurrentlyOn(TID_UI));
+#define CEF_REQUIRE_IO_THREAD()       DCHECK(CefCurrentlyOn(TID_IO));
+#define CEF_REQUIRE_FILE_THREAD()     DCHECK(CefCurrentlyOn(TID_FILE));
 #define CEF_REQUIRE_RENDERER_THREAD() DCHECK(CefCurrentlyOn(TID_RENDERER));
 
 #endif  // CEF_LIBCEF_DLL_CEF_LOGGING_H_

libcef_dll/cpptoc/read_handler_cpptoc.cc

@@ -82,6 +82,20 @@ int CEF_CALLBACK read_handler_eof(struct _cef_read_handler_t* self) {
   return _retval;
 }
 
+int CEF_CALLBACK read_handler_may_block(struct _cef_read_handler_t* self) {
+  // AUTO-GENERATED CONTENT - DELETE THIS COMMENT BEFORE MODIFYING
+
+  DCHECK(self);
+  if (!self)
+    return 0;
+
+  // Execute
+  bool _retval = CefReadHandlerCppToC::Get(self)->MayBlock();
+
+  // Return type: bool
+  return _retval;
+}
+
 
 // CONSTRUCTOR - Do not edit by hand.
 
@@ -91,6 +105,7 @@ CefReadHandlerCppToC::CefReadHandlerCppToC(CefReadHandler* cls)
   struct_.struct_.seek = read_handler_seek;
   struct_.struct_.tell = read_handler_tell;
   struct_.struct_.eof = read_handler_eof;
+  struct_.struct_.may_block = read_handler_may_block;
 }
 
 #ifndef NDEBUG

libcef_dll/cpptoc/stream_reader_cpptoc.cc

@@ -138,6 +138,20 @@ int CEF_CALLBACK stream_reader_eof(struct _cef_stream_reader_t* self) {
   return _retval;
 }
 
+int CEF_CALLBACK stream_reader_may_block(struct _cef_stream_reader_t* self) {
+  // AUTO-GENERATED CONTENT - DELETE THIS COMMENT BEFORE MODIFYING
+
+  DCHECK(self);
+  if (!self)
+    return 0;
+
+  // Execute
+  bool _retval = CefStreamReaderCppToC::Get(self)->MayBlock();
+
+  // Return type: bool
+  return _retval;
+}
+
 
 // CONSTRUCTOR - Do not edit by hand.
 
@@ -148,6 +162,7 @@ CefStreamReaderCppToC::CefStreamReaderCppToC(CefStreamReader* cls)
   struct_.struct_.seek = stream_reader_seek;
   struct_.struct_.tell = stream_reader_tell;
   struct_.struct_.eof = stream_reader_eof;
+  struct_.struct_.may_block = stream_reader_may_block;
 }
 
 #ifndef NDEBUG

libcef_dll/cpptoc/stream_writer_cpptoc.cc

@@ -120,6 +120,20 @@ int CEF_CALLBACK stream_writer_flush(struct _cef_stream_writer_t* self) {
   return _retval;
 }
 
+int CEF_CALLBACK stream_writer_may_block(struct _cef_stream_writer_t* self) {
+  // AUTO-GENERATED CONTENT - DELETE THIS COMMENT BEFORE MODIFYING
+
+  DCHECK(self);
+  if (!self)
+    return 0;
+
+  // Execute
+  bool _retval = CefStreamWriterCppToC::Get(self)->MayBlock();
+
+  // Return type: bool
+  return _retval;
+}
+
 
 // CONSTRUCTOR - Do not edit by hand.
 
@@ -130,6 +144,7 @@ CefStreamWriterCppToC::CefStreamWriterCppToC(CefStreamWriter* cls)
   struct_.struct_.seek = stream_writer_seek;
   struct_.struct_.tell = stream_writer_tell;
   struct_.struct_.flush = stream_writer_flush;
+  struct_.struct_.may_block = stream_writer_may_block;
 }
 
 #ifndef NDEBUG

libcef_dll/cpptoc/write_handler_cpptoc.cc

@@ -82,6 +82,20 @@ int CEF_CALLBACK write_handler_flush(struct _cef_write_handler_t* self) {
   return _retval;
 }
 
+int CEF_CALLBACK write_handler_may_block(struct _cef_write_handler_t* self) {
+  // AUTO-GENERATED CONTENT - DELETE THIS COMMENT BEFORE MODIFYING
+
+  DCHECK(self);
+  if (!self)
+    return 0;
+
+  // Execute
+  bool _retval = CefWriteHandlerCppToC::Get(self)->MayBlock();
+
+  // Return type: bool
+  return _retval;
+}
+
 
 // CONSTRUCTOR - Do not edit by hand.
 
@@ -92,6 +106,7 @@ CefWriteHandlerCppToC::CefWriteHandlerCppToC(CefWriteHandler* cls)
   struct_.struct_.seek = write_handler_seek;
   struct_.struct_.tell = write_handler_tell;
   struct_.struct_.flush = write_handler_flush;
+  struct_.struct_.may_block = write_handler_may_block;
 }
 
 #ifndef NDEBUG

libcef_dll/ctocpp/read_handler_ctocpp.cc

@@ -77,6 +77,19 @@ int CefReadHandlerCToCpp::Eof() {
   return _retval;
 }
 
+bool CefReadHandlerCToCpp::MayBlock() {
+  if (CEF_MEMBER_MISSING(struct_, may_block))
+    return false;
+
+  // AUTO-GENERATED CONTENT - DELETE THIS COMMENT BEFORE MODIFYING
+
+  // Execute
+  int _retval = struct_->may_block(struct_);
+
+  // Return type: bool
+  return _retval?true:false;
+}
+
 
 #ifndef NDEBUG
 template<> long CefCToCpp<CefReadHandlerCToCpp, CefReadHandler,

libcef_dll/ctocpp/read_handler_ctocpp.h

@@ -38,6 +38,7 @@ class CefReadHandlerCToCpp
   virtual int Seek(int64 offset, int whence) OVERRIDE;
   virtual int64 Tell() OVERRIDE;
   virtual int Eof() OVERRIDE;
+  virtual bool MayBlock() OVERRIDE;
 };
 
 #endif  // BUILDING_CEF_SHARED

libcef_dll/ctocpp/stream_reader_ctocpp.cc

@@ -133,6 +133,19 @@ int CefStreamReaderCToCpp::Eof() {
   return _retval;
 }
 
+bool CefStreamReaderCToCpp::MayBlock() {
+  if (CEF_MEMBER_MISSING(struct_, may_block))
+    return false;
+
+  // AUTO-GENERATED CONTENT - DELETE THIS COMMENT BEFORE MODIFYING
+
+  // Execute
+  int _retval = struct_->may_block(struct_);
+
+  // Return type: bool
+  return _retval?true:false;
+}
+
 
 #ifndef NDEBUG
 template<> long CefCToCpp<CefStreamReaderCToCpp, CefStreamReader,

libcef_dll/ctocpp/stream_reader_ctocpp.h

@@ -38,6 +38,7 @@ class CefStreamReaderCToCpp
   virtual int Seek(int64 offset, int whence) OVERRIDE;
   virtual int64 Tell() OVERRIDE;
   virtual int Eof() OVERRIDE;
+  virtual bool MayBlock() OVERRIDE;
 };
 
 #endif  // USING_CEF_SHARED

libcef_dll/ctocpp/stream_writer_ctocpp.cc

@@ -115,6 +115,19 @@ int CefStreamWriterCToCpp::Flush() {
   return _retval;
 }
 
+bool CefStreamWriterCToCpp::MayBlock() {
+  if (CEF_MEMBER_MISSING(struct_, may_block))
+    return false;
+
+  // AUTO-GENERATED CONTENT - DELETE THIS COMMENT BEFORE MODIFYING
+
+  // Execute
+  int _retval = struct_->may_block(struct_);
+
+  // Return type: bool
+  return _retval?true:false;
+}
+
 
 #ifndef NDEBUG
 template<> long CefCToCpp<CefStreamWriterCToCpp, CefStreamWriter,

libcef_dll/ctocpp/stream_writer_ctocpp.h

@@ -38,6 +38,7 @@ class CefStreamWriterCToCpp
   virtual int Seek(int64 offset, int whence) OVERRIDE;
   virtual int64 Tell() OVERRIDE;
   virtual int Flush() OVERRIDE;
+  virtual bool MayBlock() OVERRIDE;
 };
 
 #endif  // USING_CEF_SHARED

libcef_dll/ctocpp/write_handler_ctocpp.cc

@@ -77,6 +77,19 @@ int CefWriteHandlerCToCpp::Flush() {
   return _retval;
 }
 
+bool CefWriteHandlerCToCpp::MayBlock() {
+  if (CEF_MEMBER_MISSING(struct_, may_block))
+    return false;
+
+  // AUTO-GENERATED CONTENT - DELETE THIS COMMENT BEFORE MODIFYING
+
+  // Execute
+  int _retval = struct_->may_block(struct_);
+
+  // Return type: bool
+  return _retval?true:false;
+}
+
 
 #ifndef NDEBUG
 template<> long CefCToCpp<CefWriteHandlerCToCpp, CefWriteHandler,

libcef_dll/ctocpp/write_handler_ctocpp.h

@@ -38,6 +38,7 @@ class CefWriteHandlerCToCpp
   virtual int Seek(int64 offset, int whence) OVERRIDE;
   virtual int64 Tell() OVERRIDE;
   virtual int Flush() OVERRIDE;
+  virtual bool MayBlock() OVERRIDE;
 };
 
 #endif  // BUILDING_CEF_SHARED

libcef_dll/wrapper/cef_stream_resource_handler.cc

@@ -3,32 +3,119 @@
 // can be found in the LICENSE file.
 
 #include "include/wrapper/cef_stream_resource_handler.h"
+#include <algorithm>
 #include "include/cef_callback.h"
 #include "include/cef_request.h"
+#include "include/cef_runnable.h"
 #include "include/cef_stream.h"
 #include "libcef_dll/cef_logging.h"
 
+// Class that represents a readable/writable character buffer.
+class CefStreamResourceHandler::Buffer {
+ public:
+  Buffer()
+      : buffer_(NULL),
+        size_(0),
+        bytes_requested_(0),
+        bytes_written_(0),
+        bytes_read_(0) {
+  }
+
+  ~Buffer() {
+    if (buffer_)
+      delete [] buffer_;
+  }
+
+  void Reset(int new_size) {
+    if (size_ < new_size) {
+      if (buffer_)
+        delete [] buffer_;
+      size_ = new_size;
+      buffer_ = new char[size_];
+      DCHECK(buffer_);
+    }
+    bytes_requested_ = new_size;
+    bytes_written_ = 0;
+    bytes_read_ = 0;
+  }
+
+  bool IsEmpty() const {
+    return (bytes_written_ == 0);
+  }
+
+  bool CanRead() const {
+    return (bytes_read_ < bytes_written_);
+  }
+
+  int WriteTo(void* data_out, int bytes_to_read) {
+    const int write_size =
+        std::min(bytes_to_read, bytes_written_ - bytes_read_);
+    if (write_size > 0) {
+      memcpy(data_out, buffer_  + bytes_read_, write_size);
+      bytes_read_ += write_size;
+    }
+    return write_size;
+  }
+
+  int ReadFrom(CefRefPtr<CefStreamReader> reader) {
+    // Read until the buffer is full or until Read() returns 0 to indicate no
+    // more data.
+    int bytes_read;
+    do {
+      bytes_read = static_cast<int>(
+          reader->Read(buffer_ + bytes_written_, 1,
+                       bytes_requested_ - bytes_written_));
+      bytes_written_ += bytes_read;
+    } while (bytes_read != 0 && bytes_written_ < bytes_requested_);
+
+    return bytes_written_;
+  }
+
+ private:
+  char* buffer_;
+  int size_;
+  int bytes_requested_;
+  int bytes_written_;
+  int bytes_read_;
+};
+
 CefStreamResourceHandler::CefStreamResourceHandler(
     const CefString& mime_type,
     CefRefPtr<CefStreamReader> stream)
     : status_code_(200),
+      status_text_("OK"),
       mime_type_(mime_type),
-      stream_(stream) {
+      stream_(stream),
+      buffer_(NULL)
+#ifndef NDEBUG
+      , buffer_owned_by_file_thread_(false)
+#endif
+{
   DCHECK(!mime_type_.empty());
   DCHECK(stream_.get());
+  read_on_file_thread_ = stream_->MayBlock();
 }
 
 CefStreamResourceHandler::CefStreamResourceHandler(
     int status_code,
+    const CefString& status_text,
     const CefString& mime_type,
     CefResponse::HeaderMap header_map,
     CefRefPtr<CefStreamReader> stream)
     : status_code_(status_code),
+      status_text_(status_text),
       mime_type_(mime_type),
       header_map_(header_map),
-      stream_(stream) {
+      stream_(stream),
+      buffer_(NULL) {
   DCHECK(!mime_type_.empty());
   DCHECK(stream_.get());
+  read_on_file_thread_ = stream_->MayBlock();
+}
+
+CefStreamResourceHandler::~CefStreamResourceHandler() {
+  if (buffer_)
+    delete buffer_;
 }
 
 bool CefStreamResourceHandler::ProcessRequest(CefRefPtr<CefRequest> request,
@@ -42,6 +129,7 @@ void CefStreamResourceHandler::GetResponseHeaders(
     int64& response_length,
     CefString& redirectUrl) {
   response->SetStatus(status_code_);
+  response->SetStatusText(status_text_);
   response->SetMimeType(mime_type_);
 
   if (!header_map_.empty())
@@ -54,9 +142,63 @@ bool CefStreamResourceHandler::ReadResponse(void* data_out,
                                             int bytes_to_read,
                                             int& bytes_read,
                                             CefRefPtr<CefCallback> callback) {
-  bytes_read = static_cast<int>(stream_->Read(data_out, 1, bytes_to_read));
-  return (bytes_read > 0);
+  DCHECK_GT(bytes_to_read, 0);
+
+  if (read_on_file_thread_) {
+    DCHECK(!buffer_owned_by_file_thread_);
+    if (buffer_ && (buffer_->CanRead() || buffer_->IsEmpty())) {
+      if (buffer_->CanRead()) {
+        // Provide data from the buffer.
+        bytes_read = buffer_->WriteTo(data_out, bytes_to_read);
+        return (bytes_read > 0);
+      } else {
+        // End of the steam.
+        bytes_read = 0;
+        return false;
+      }
+    } else {
+      // Perform another read on the file thread.
+      bytes_read = 0;
+#ifndef NDEBUG
+      buffer_owned_by_file_thread_ = true;
+#endif
+      CefPostTask(TID_FILE,
+          NewCefRunnableMethod(this, &CefStreamResourceHandler::ReadOnFileThread,
+                               bytes_to_read, callback));
+      return true;
+    }
+  } else {
+    // Read until the buffer is full or until Read() returns 0 to indicate no
+    // more data.
+    bytes_read = 0;
+    int read = 0;
+    do {
+      read = static_cast<int>(
+          stream_->Read(static_cast<char*>(data_out) + bytes_read, 1,
+                        bytes_to_read - bytes_read));
+      bytes_read += read;
+    } while (read != 0 && bytes_read < bytes_to_read);
+
+    return (bytes_read > 0);
+  }
 }
 
 void CefStreamResourceHandler::Cancel() {
 }
+
+void CefStreamResourceHandler::ReadOnFileThread(
+    int bytes_to_read,
+    CefRefPtr<CefCallback> callback) {
+  CEF_REQUIRE_FILE_THREAD();
+  DCHECK(buffer_owned_by_file_thread_);
+
+  if (!buffer_)
+    buffer_ = new Buffer();
+  buffer_->Reset(bytes_to_read);
+  buffer_->ReadFrom(stream_);
+
+#ifndef NDEBUG
+  buffer_owned_by_file_thread_ = false;
+#endif
+  callback->Continue();
+}

tests/unittests/stream_resource_handler_unittest.cc

@@ -0,0 +1,159 @@
+// Copyright (c) 2014 The Chromium Embedded Framework 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 <algorithm>
+#include <cstdlib>
+#include <string>
+#include "include/cef_stream.h"
+#include "include/wrapper/cef_stream_resource_handler.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include "tests/unittests/routing_test_handler.h"
+
+namespace {
+
+const char kTestUrl[] = "http://tests-srh/test.html";
+const size_t kReadBlockSize = 1024U;  // 1k.
+
+// The usual network buffer size is about 32k. Choose a value that's larger.
+const size_t kReadDesiredSize = 100U * 1024U;  // 100k
+
+class ReadHandler : public CefReadHandler {
+ public:
+  explicit ReadHandler(bool may_block)
+    : may_block_(may_block),
+      offset_(0),
+      expected_result_(0) {
+  }
+
+  void CreateContent() {
+    // To verify that the data transers successfully we're going to make a big
+    // math problem.
+    content_.reserve(kReadDesiredSize + 50U);
+    content_ = "<html><body><script>var myratherlongvariablename=0;";
+
+    while (content_.size() < kReadDesiredSize) {
+      content_ += "myratherlongvariablename=myratherlongvariablename+1;";
+      expected_result_++;
+    }
+
+    content_ += "window.testQuery({request:myratherlongvariablename+''});"
+                "</script></body></html>";
+  }
+
+  int GetExpectedResult() const {
+    return expected_result_;
+  }
+
+  virtual size_t Read(void* ptr, size_t size, size_t n) OVERRIDE {
+    EXPECT_EQ(1, size);
+
+    // Read the minimum of requested size, remaining size or kReadBlockSize.
+    const size_t read_bytes =
+        std::min(std::min(size * n, content_.size() - offset_), kReadBlockSize);
+    if (read_bytes > 0) {
+      memcpy(ptr, content_.c_str() + offset_, read_bytes);
+      offset_ += read_bytes;
+    }
+
+    return read_bytes;
+  }
+
+  virtual int Seek(int64 offset, int whence) OVERRIDE {
+    EXPECT_TRUE(false);  // Not reached.
+    return 0;
+  }
+
+  virtual int64 Tell() OVERRIDE {
+    EXPECT_TRUE(false);  // Not reached.
+    return 0;
+  }
+
+  virtual int Eof() OVERRIDE {
+    EXPECT_TRUE(false);  // Not reached.
+    return 0;
+  }
+
+  virtual bool MayBlock() OVERRIDE {
+    return may_block_;
+  }
+
+ private:
+  const bool may_block_;
+  std::string content_;
+  size_t offset_;
+  int expected_result_;
+
+  IMPLEMENT_REFCOUNTING(StreamReader);
+};
+
+class ReadTestHandler : public RoutingTestHandler {
+ public:
+  explicit ReadTestHandler(bool may_block)
+      : may_block_(may_block),
+        expected_result_(0) {}
+
+  virtual void RunTest() OVERRIDE {
+    // Create the browser.
+    CreateBrowser(kTestUrl);
+  }
+
+  virtual CefRefPtr<CefResourceHandler> GetResourceHandler(
+      CefRefPtr<CefBrowser> browser,
+      CefRefPtr<CefFrame> frame,
+      CefRefPtr<CefRequest> request) OVERRIDE {
+    got_resource_handler_.yes();
+
+    const std::string& url = request->GetURL();
+    EXPECT_STREQ(kTestUrl, url.c_str());
+
+    CefRefPtr<ReadHandler> handler = new ReadHandler(may_block_);
+    handler->CreateContent();
+    expected_result_ = handler->GetExpectedResult();
+
+    CefRefPtr<CefStreamReader> stream =
+        CefStreamReader::CreateForHandler(handler.get());
+    return new CefStreamResourceHandler("text/html", stream);
+  }
+
+  virtual bool OnQuery(CefRefPtr<CefBrowser> browser,
+                       CefRefPtr<CefFrame> frame,
+                       int64 query_id,
+                       const CefString& request,
+                       bool persistent,
+                       CefRefPtr<Callback> callback) OVERRIDE {
+    got_on_query_.yes();
+
+    const int actual_result = atoi(request.ToString().c_str());
+    EXPECT_EQ(expected_result_, actual_result);
+
+    DestroyTest();
+
+    return true;
+  }
+
+ private:
+  virtual void DestroyTest() OVERRIDE {
+    EXPECT_TRUE(got_resource_handler_);
+    EXPECT_TRUE(got_on_query_);
+    RoutingTestHandler::DestroyTest();
+  }
+
+  const bool may_block_;
+
+  int expected_result_;
+  TrackCallback got_resource_handler_;
+  TrackCallback got_on_query_;
+};
+
+}  // namespace
+
+TEST(StreamResourceHandlerTest, ReadWillBlock) {
+  CefRefPtr<ReadTestHandler> handler = new ReadTestHandler(true);
+  handler->ExecuteTest();
+}
+
+TEST(StreamResourceHandlerTest, ReadWontBlock) {
+  CefRefPtr<ReadTestHandler> handler = new ReadTestHandler(false);
+  handler->ExecuteTest();
+}

tests/unittests/stream_unittest.cc

@@ -87,6 +87,7 @@ TEST(StreamTest, ReadFile) {
   CefRefPtr<CefStreamReader> stream(
       CefStreamReader::CreateForFile(fileNameStr));
   ASSERT_TRUE(stream.get() != NULL);
+  ASSERT_TRUE(stream->MayBlock());
   VerifyStreamReadBehavior(stream, contents);
 
   // Release the file pointer
@@ -109,6 +110,7 @@ TEST(StreamTest, ReadData) {
           static_cast<void*>(const_cast<char*>(contents.c_str())),
           contents.size()));
   ASSERT_TRUE(stream.get() != NULL);
+  ASSERT_FALSE(stream->MayBlock());
   VerifyStreamReadBehavior(stream, contents);
 }
 
@@ -121,6 +123,7 @@ TEST(StreamTest, WriteFile) {
   CefRefPtr<CefStreamWriter> stream(
       CefStreamWriter::CreateForFile(fileNameStr));
   ASSERT_TRUE(stream.get() != NULL);
+  ASSERT_TRUE(stream->MayBlock());
   VerifyStreamWriteBehavior(stream, contents);
 
   // Release the file pointer
@@ -173,7 +176,7 @@ class ReadHandlerTester : public CefReadHandler {
     g_ReadHandlerTesterDeleted = true;
   }
 
-  virtual size_t Read(void* ptr, size_t size, size_t n) {
+  virtual size_t Read(void* ptr, size_t size, size_t n) OVERRIDE {
     read_called_ = true;
     read_ptr_ = ptr;
     read_size_ = size;
@@ -181,23 +184,27 @@ class ReadHandlerTester : public CefReadHandler {
     return 10;
   }
 
-  virtual int Seek(int64 offset, int whence) {
+  virtual int Seek(int64 offset, int whence) OVERRIDE {
     seek_called_ = true;
     seek_offset_ = offset;
     seek_whence_ = whence;
     return 10;
   }
 
-  virtual int64 Tell() {
+  virtual int64 Tell() OVERRIDE {
     tell_called_ = true;
     return 10;
   }
 
-  virtual int Eof() {
+  virtual int Eof() OVERRIDE {
     eof_called_ = true;
     return 10;
   }
 
+  virtual bool MayBlock() OVERRIDE {
+    return false;
+  }
+
   bool read_called_;
   const void* read_ptr_;
   size_t read_size_;
@@ -220,6 +227,7 @@ TEST(StreamTest, ReadHandler) {
 
   CefRefPtr<CefStreamReader> stream(CefStreamReader::CreateForHandler(handler));
   ASSERT_TRUE(stream.get() != NULL);
+  ASSERT_FALSE(stream->MayBlock());
 
   // CefReadHandler Read
   const char* read_ptr = "My data";
@@ -278,7 +286,7 @@ class WriteHandlerTester : public CefWriteHandler {
     g_WriteHandlerTesterDeleted = true;
   }
 
-  virtual size_t Write(const void* ptr, size_t size, size_t n) {
+  virtual size_t Write(const void* ptr, size_t size, size_t n) OVERRIDE {
     write_called_ = true;
     write_ptr_ = ptr;
     write_size_ = size;
@@ -286,23 +294,27 @@ class WriteHandlerTester : public CefWriteHandler {
     return 10;
   }
 
-  virtual int Seek(int64 offset, int whence) {
+  virtual int Seek(int64 offset, int whence) OVERRIDE {
     seek_called_ = true;
     seek_offset_ = offset;
     seek_whence_ = whence;
     return 10;
   }
 
-  virtual int64 Tell() {
+  virtual int64 Tell() OVERRIDE {
     tell_called_ = true;
     return 10;
   }
 
-  virtual int Flush() {
+  virtual int Flush() OVERRIDE {
     flush_called_ = true;
     return 10;
   }
 
+  virtual bool MayBlock() OVERRIDE {
+    return false;
+  }
+
   bool write_called_;
   const void* write_ptr_;
   size_t write_size_;
@@ -325,6 +337,7 @@ TEST(StreamTest, WriteHandler) {
 
   CefRefPtr<CefStreamWriter> stream(CefStreamWriter::CreateForHandler(handler));
   ASSERT_TRUE(stream.get() != NULL);
+  ASSERT_FALSE(stream->MayBlock());
 
   // CefWriteHandler Write
   const char* write_ptr = "My data";