Add a safe API for creating ASCII-only strings

src/heap.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 4516 matching lines @@
         AllocateRawOneByteString(string.length(), pretenure);
     if (!maybe_result->ToObject(&result)) return maybe_result;
   }
 
   // Copy the characters into the new object.
   CopyChars(SeqOneByteString::cast(result)->GetChars(), string.start(), length);
   return result;
 }
 
 
+MaybeObject* Heap::AllocateStringFromAsciiSafe(Vector<const char> string,
+                                               PretenureFlag pretenure) {
+  if (string.length() == 1) {
+    return Heap::LookupSingleCharacterStringFromCode(string
+        [0] & String::kMaxAsciiCharCodeU);
+  }
+  Object* result;
+  { MaybeObject* maybe_result =
+        AllocateRawAsciiString(string.length(), pretenure);
+    if (!maybe_result->ToObject(&result)) return maybe_result;
+  }
+
+  // Copy the characters into the new object.
+  SeqAsciiString* string_result = SeqAsciiString::cast(result);
+  for (int i = 0; i < string.length(); i++) {
+    string_result->SeqAsciiStringSet(i,

[bnoordhuis1, 2012/12/07 04:54:47]

AllocateRawAsciiString and SeqAsciiString don't exist in HEAD.

+                                     string[i] & String::kMaxAsciiCharCodeU);
+  }
+  return result;
+}
+
+
 MaybeObject* Heap::AllocateStringFromUtf8Slow(Vector<const char> string,
                                               int non_ascii_start,
                                               PretenureFlag pretenure) {
   // Continue counting the number of characters in the UTF-8 string, starting
   // from the first non-ascii character or word.
   int chars = non_ascii_start;
   Access<UnicodeCache::Utf8Decoder>
       decoder(isolate_->unicode_cache()->utf8_decoder());
   decoder->Reset(string.start() + non_ascii_start, string.length() - chars);
   while (decoder->has_more()) {
@@ skipping 2739 matching lines @@
       static_cast<int>(object_sizes_last_time_[index]));
   FIXED_ARRAY_SUB_INSTANCE_TYPE_LIST(ADJUST_LAST_TIME_OBJECT_COUNT)
 #undef ADJUST_LAST_TIME_OBJECT_COUNT
 
   memcpy(object_counts_last_time_, object_counts_, sizeof(object_counts_));
   memcpy(object_sizes_last_time_, object_sizes_, sizeof(object_sizes_));
   ClearObjectStats();
 }
 
 } }  // namespace v8::internal