Changes to make isolate reload functionality work with the --dfe option.

runtime/bin/dfe.cc

+// Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+#include "bin/dfe.h"
+#include "bin/dartutils.h"
+
+namespace dart {
+namespace bin {
+
+DFE::DFE() : frontend_filename_(NULL), platform_binary_filename_(NULL) {}
+
+
+DFE::~DFE() {
+  frontend_filename_ = NULL;
+  platform_binary_filename_ = NULL;
+}
+
+Dart_Handle DFE::ReloadScript(Dart_Isolate isolate, Dart_Handle url) {
+  ASSERT(!Dart_IsServiceIsolate(isolate) && !Dart_IsKernelIsolate(isolate));
+  const char* url_string = NULL;
+  Dart_Handle result = Dart_StringToCString(url, &url_string);
+  if (Dart_IsError(result)) {
+    return result;
+  }
+  // First check if the URL points to a Kernel IR file in which case we
+  // skip the compilation step and directly reload the file.
+  const uint8_t* kernel_ir = NULL;
+  intptr_t kernel_ir_size = -1;
+  if (!TryReadKernelFile(url_string, &kernel_ir, &kernel_ir_size)) {
+    // We have a source file, compile it into a kernel ir first.
+    // TODO(asiva): We will have to change this API to pass in a list of files
+    // that have changed. For now just pass in the main url_string and have it
+    // recompile the script.
+    Dart_KernelCompilationResult kresult = Dart_CompileToKernel(url_string);
+    if (kresult.status != Dart_KernelCompilationStatus_Ok) {
+      return Dart_NewApiError(kresult.error);
+    }
+    kernel_ir = kresult.kernel;
+    kernel_ir_size = kresult.kernel_size;
+  }
+  void* kernel_program = Dart_ReadKernelBinary(kernel_ir, kernel_ir_size);
+  ASSERT(kernel_program != NULL);
+  result = Dart_LoadKernel(kernel_program);
+  if (Dart_IsError(result)) {
+    return result;
+  }
+  // Finalize loading. This will complete any futures for completed deferred
+  // loads.
+  result = Dart_FinalizeLoading(true);
+  if (Dart_IsError(result)) {
+    return result;
+  }
+  return Dart_Null();
+}
+
+
+bool DFE::TryReadKernelFile(const char* script_uri,
+                            const uint8_t** kernel_ir,
+                            intptr_t* kernel_ir_size) {
+  *kernel_ir = NULL;
+  *kernel_ir_size = -1;
+  void* script_file = DartUtils::OpenFile(script_uri, false);
+  if (script_file != NULL) {
+    const uint8_t* buffer = NULL;
+    DartUtils::ReadFile(&buffer, kernel_ir_size, script_file);
+    DartUtils::CloseFile(script_file);
+    if (*kernel_ir_size > 0 && buffer != NULL) {
+      // We need a temporary variable because SniffForMagicNumber modifies the
+      // buffer pointer to skip snapshot magic number.
+      const uint8_t* temp = buffer;
+      if (DartUtils::SniffForMagicNumber(&temp, kernel_ir_size) !=
+          DartUtils::kKernelMagicNumber) {
+        free(const_cast<uint8_t*>(buffer));
+        *kernel_ir = NULL;
+        *kernel_ir_size = -1;
+        return false;
+      } else {
+        // Do not free buffer if this is a kernel file - kernel_file will be
+        // backed by the same memory as the buffer and caller will own it.
+        // Caller is responsible for freeing the buffer when this function
+        // returns true.
+        *kernel_ir = buffer;
+        return true;
+      }
+    }
+  }
+  return false;
+}
+
+
+}  // namespace bin
+}  // namespace dart