Use offset and count to request slices of lists, maps, and typed_data.

runtime/vm/service.cc

 // Copyright (c) 2013, 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 "vm/service.h"
 
 #include "include/dart_api.h"
 #include "include/dart_native_api.h"
 #include "platform/globals.h"
 
@@ skipping 2812 matching lines @@
 static bool RespondWithMalformedObject(Isolate* isolate,
                                         JSONStream* js) {
   JSONObject jsobj(js);
   jsobj.AddProperty("bart", "simpson");
   return true;
 }
 
 
 static const MethodParameter* get_object_params[] = {
   ISOLATE_PARAMETER,
+  new UIntParameter("offset", false),
+  new UIntParameter("count", false),
   NULL,
 };
 
 
 static bool GetObject(Isolate* isolate, JSONStream* js) {
   const char* id = js->LookupParam("objectId");
   if (id == NULL) {
     PrintMissingParamError(js, "objectId");
     return true;
   }
+  if (js->HasParam("offset")) {
+    intptr_t value = UIntParameter::Parse(js->LookupParam("offset"));
+    if (value < 0) {
+      PrintInvalidParamError(js, "offset");
+      return true;
+    }
+    js->set_offset(value);
+  }
+  if (js->HasParam("count")) {
+    intptr_t value = UIntParameter::Parse(js->LookupParam("count"));
+    if (value < 1) {

[Cutch, 2015/10/14 17:58:09]

Consider allowing queries of the container with a zero count.

[turnidge, 2015/10/14 18:02:42]

Done.

+      PrintInvalidParamError(js, "count");
+      return true;
+    }
+    js->set_count(value);
+  }
 
   // Handle heap objects.
   ObjectIdRing::LookupResult lookup_result;
   const Object& obj =
       Object::Handle(LookupHeapObject(isolate, id, &lookup_result));
   if (obj.raw() != Object::sentinel().raw()) {
     // We found a heap object for this id.  Return it.
     obj.PrintJSON(js, false);
     return true;
   } else if (lookup_result == ObjectIdRing::kCollected) {
@@ skipping 427 matching lines @@
     ServiceMethodDescriptor& method = service_methods_[i];
     if (strcmp(method_name, method.name) == 0) {
       return &method;
     }
   }
   return NULL;
 }
 
 
 }  // namespace dart