Improve WriteUtf8 and WriteAscii.

src/api.cc

 // Copyright 2011 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 3624 matching lines @@
 
 int String::WriteUtf8(char* buffer,
                       int capacity,
                       int* nchars_ref,
                       int options) const {
   i::Isolate* isolate = Utils::OpenHandle(this)->GetIsolate();
   if (IsDeadCheck(isolate, "v8::String::WriteUtf8()")) return 0;
   LOG_API(isolate, "String::WriteUtf8");
   ENTER_V8(isolate);
   i::Handle<i::String> str = Utils::OpenHandle(this);
+  if (options & HINT_MANY_WRITES_EXPECTED) {
+    // Flatten the string for efficiency.  This applies whether we are
+    // using StringInputBuffer or Get(i) to access the characters.
+    FlattenString(str);
+  }
   if (str->IsAsciiRepresentation()) {
     int len;
     if (capacity == -1) {
       capacity = str->length() + 1;
       len = str->length();
     } else {
       len = i::Min(capacity, str->length());
     }
     i::String::WriteToFlat(*str, buffer, 0, len);
     if (nchars_ref != NULL) *nchars_ref = len;
     if (!(options & NO_NULL_TERMINATION) && capacity > len) {
       buffer[len] = '\0';
       return len + 1;
     }
     return len;
   }
 
   i::StringInputBuffer& write_input_buffer = *isolate->write_input_buffer();
   isolate->string_tracker()->RecordWrite(str);
-  if (options & HINT_MANY_WRITES_EXPECTED) {
-    // Flatten the string for efficiency.  This applies whether we are
-    // using StringInputBuffer or Get(i) to access the characters.
-    FlattenString(str);
-  }
+
   write_input_buffer.Reset(0, *str);
   int len = str->length();
   // Encode the first K - 3 bytes directly into the buffer since we
   // know there's room for them.  If no capacity is given we copy all
   // of them here.
   int fast_end = capacity - (unibrow::Utf8::kMaxEncodedSize - 1);
   int i;
   int pos = 0;
   int nchars = 0;
   for (i = 0; i < len && (capacity == -1 || pos < fast_end); i++) {
@@ skipping 37 matching lines @@
   if (IsDeadCheck(isolate, "v8::String::WriteAscii()")) return 0;
   LOG_API(isolate, "String::WriteAscii");
   ENTER_V8(isolate);
   i::StringInputBuffer& write_input_buffer = *isolate->write_input_buffer();
   ASSERT(start >= 0 && length >= -1);
   i::Handle<i::String> str = Utils::OpenHandle(this);
   isolate->string_tracker()->RecordWrite(str);
   if (options & HINT_MANY_WRITES_EXPECTED) {
     // Flatten the string for efficiency.  This applies whether we are
     // using StringInputBuffer or Get(i) to access the characters.
-    str->TryFlatten();
+    FlattenString(str);
   }
+  if (str->IsAsciiRepresentation()) {
+    if (length == -1) length = str->length() + 1;
+    int len = i::Min(length, str->length() - start);
+    i::String::WriteToFlat(*str, buffer, start, start + len);
+    for (int i = 0; i < len; i++) {
+      if (buffer[i] == '\0') buffer[i] = ' ';
+    }
+    if (!(options & NO_NULL_TERMINATION) && length > len) {
+      buffer[len] = '\0';
+    }
+    return len;
+  }
+
   int end = length;
   if ( (length == -1) || (length > str->length() - start) )
     end = str->length() - start;
   if (end < 0) return 0;
   write_input_buffer.Reset(start, *str);
   int i;
   for (i = 0; i < end; i++) {
     char c = static_cast<char>(write_input_buffer.GetNext());
     if (c == '\0') c = ' ';
     buffer[i] = c;
@@ skipping 11 matching lines @@
   i::Isolate* isolate = Utils::OpenHandle(this)->GetIsolate();
   if (IsDeadCheck(isolate, "v8::String::Write()")) return 0;
   LOG_API(isolate, "String::Write");
   ENTER_V8(isolate);
   ASSERT(start >= 0 && length >= -1);
   i::Handle<i::String> str = Utils::OpenHandle(this);
   isolate->string_tracker()->RecordWrite(str);
   if (options & HINT_MANY_WRITES_EXPECTED) {
     // Flatten the string for efficiency.  This applies whether we are
     // using StringInputBuffer or Get(i) to access the characters.
-    str->TryFlatten();
+    FlattenString(str);
   }
   int end = start + length;
   if ((length == -1) || (length > str->length() - start) )
     end = str->length();
   if (end < 0) return 0;
   i::String::WriteToFlat(*str, buffer, start, end);
   if (!(options & NO_NULL_TERMINATION) &&
       (length == -1 || end - start < length)) {
     buffer[end - start] = '\0';
   }
@@ skipping 2330 matching lines @@
 
 
 char* HandleScopeImplementer::Iterate(ObjectVisitor* v, char* storage) {
   HandleScopeImplementer* scope_implementer =
       reinterpret_cast<HandleScopeImplementer*>(storage);
   scope_implementer->IterateThis(v);
   return storage + ArchiveSpacePerThread();
 }
 
 } }  // namespace v8::internal