getObject now supports specifying offset,count for strings.

runtime/vm/json_stream.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 "platform/assert.h"
 
 #include "vm/dart_entry.h"
 #include "vm/debugger.h"
 #include "vm/json_stream.h"
 #include "vm/message.h"
@@ skipping 378 matching lines @@
 
 
 void JSONStream::PrintValue(const char* s) {
   PrintCommaIfNeeded();
   buffer_.AddChar('"');
   AddEscapedUTF8String(s);
   buffer_.AddChar('"');
 }
 
 
-bool JSONStream::PrintValueStr(const String& s, intptr_t limit) {
+bool JSONStream::PrintValueStr(const String& s,
+                               intptr_t offset,
+                               intptr_t count) {
   PrintCommaIfNeeded();
   buffer_.AddChar('"');
-  bool did_truncate = AddDartString(s, limit);
+  bool did_truncate = AddDartString(s, offset, count);
   buffer_.AddChar('"');
   return did_truncate;
 }
 
 
 void JSONStream::PrintValueNoEscape(const char* s) {
   PrintCommaIfNeeded();
   buffer_.Printf("%s", s);
 }
 
@@ skipping 114 matching lines @@
 void JSONStream::PrintPropertyBase64(const char* name,
                                      const uint8_t* b,
                                      intptr_t len) {
   PrintPropertyName(name);
   PrintValueBase64(b, len);
 }
 
 
 bool JSONStream::PrintPropertyStr(const char* name,
                                   const String& s,
-                                  intptr_t limit) {
+                                  intptr_t offset,
+                                  intptr_t count) {
   PrintPropertyName(name);
-  return PrintValueStr(s, limit);
+  return PrintValueStr(s, offset, count);
 }
 
 
 void JSONStream::PrintPropertyNoEscape(const char* name, const char* s) {
   PrintPropertyName(name);
   PrintValueNoEscape(s);
 }
 
 
 void JSONStream::PrintProperty(const char* name, const ServiceEvent* event) {
@@ skipping 145 matching lines @@
     int32_t ch_len = Utf8::Decode(&s8[i], len - i, &ch);
     ASSERT(ch_len != 0);
     buffer_.EscapeAndAddCodeUnit(ch);
     // Move i forward.
     i += ch_len;
   }
   ASSERT(i == len);
 }
 
 
-bool JSONStream::AddDartString(const String& s, intptr_t limit) {
-  bool did_truncate = false;
+bool JSONStream::AddDartString(const String& s,
+                               intptr_t offset,
+                               intptr_t count) {
   intptr_t length = s.Length();
-  if (limit == -1) {
-    limit = length;
+  ASSERT(offset >= 0);
+  if (offset > length) {
+    offset = length;
   }
-  if (length <= limit) {
-    limit = length;
-  } else {
-    did_truncate = true;
+  if (!Utils::RangeCheck(offset, count, length)) {
+    count = length - offset;
   }
-
-  for (intptr_t i = 0; i < limit; i++) {
+  intptr_t limit = offset + count;
+  for (intptr_t i = offset; i < limit; i++) {
     intptr_t code_unit = s.CharAt(i);
     buffer_.EscapeAndAddCodeUnit(code_unit);
   }
-  return did_truncate;
+  // Return value indicates whether the string is truncated.
+  return (offset > 0) || (limit < length);
 }
 
 
 JSONObject::JSONObject(const JSONArray* arr) : stream_(arr->stream_) {
   stream_->OpenObject();
 }
 
 
 void JSONObject::AddFixedServiceId(const char* format, ...) const {
   // Mark that this id is fixed.
@@ skipping 103 matching lines @@
   intptr_t len2 = OS::VSNPrint(p, len+1, format, args);
   va_end(args);
   ASSERT(len == len2);
   stream_->buffer_.AddChar('"');
   stream_->AddEscapedUTF8String(p);
   stream_->buffer_.AddChar('"');
   free(p);
 }
 
 }  // namespace dart