Improve String::WriteAscii and add PRESERVE_ASCII_NULL option.

src/api.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 3829 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) {
+    FlattenString(str);  // Flatten the string for efficiency.
+  }
   int string_length = str->length();
   if (str->IsAsciiRepresentation()) {
     int len;
     if (capacity == -1) {
       capacity = str->length() + 1;
       len = string_length;
     } else {
       len = i::Min(capacity, str->length());
     }
     i::String::WriteToFlat(*str, buffer, 0, len);
@@ skipping 36 matching lines @@
     int utf8_bytes = i::Utf8Length(str);
     if ((options & NO_NULL_TERMINATION) == 0) utf8_bytes++;
     if (utf8_bytes <= capacity) {
       return WriteUtf8(buffer, -1, nchars_ref, options);
     }
   }
 
   // Slow case.
   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;
   int previous = unibrow::Utf16::kNoPreviousCharacter;
@@ skipping 21 matching lines @@
         int written = unibrow::Utf8::Encode(buffer + pos, c, previous);
         ASSERT(written == 1);
         pos += written;
         nchars++;
       } else {
         int written =
             unibrow::Utf8::Encode(intermediate,
                                   c,
                                   unibrow::Utf16::kNoPreviousCharacter);
         if (pos + written <= capacity) {
-          for (int j = 0; j < written; j++)
+          for (int j = 0; j < written; j++) {
             buffer[pos + j] = intermediate[j];
+          }
           pos += written;
           nchars++;
         } else {
           // We've reached the end of the buffer
           break;
         }
       }
       previous = c;
     }
   }
   if (nchars_ref != NULL) *nchars_ref = nchars;
   if (!(options & NO_NULL_TERMINATION) &&
-      (i == len && (capacity == -1 || pos < capacity)))
+      (i == len && (capacity == -1 || pos < capacity))) {
     buffer[pos++] = '\0';
+  }
   return pos;
 }
 
 
 int String::WriteAscii(char* buffer,
                        int start,
                        int length,
                        int options) const {
   i::Isolate* isolate = Utils::OpenHandle(this)->GetIsolate();
   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);  // Flatten the string for efficiency.
   }
+
+  if (str->IsAsciiRepresentation()) {
+    // WriteToFlat is faster than using the StringInputBuffer.
+    if (length == -1) length = str->length() + 1;
+    int len = i::Min(length, str->length() - start);
+    i::String::WriteToFlat(*str, buffer, start, start + len);
+    if (!(options & PRESERVE_ASCII_NULL)) {
+      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;
+  }
+
+  i::StringInputBuffer& write_input_buffer = *isolate->write_input_buffer();
   int end = length;
-  if ( (length == -1) || (length > str->length() - start) )
+  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 = ' ';
+    if (c == '\0' && !(options & PRESERVE_ASCII_NULL)) c = ' ';
     buffer[i] = c;
   }
-  if (!(options & NO_NULL_TERMINATION) && (length == -1 || i < length))
+  if (!(options & NO_NULL_TERMINATION) && (length == -1 || i < length)) {
     buffer[i] = '\0';
+  }
   return i;
 }
 
 
 int String::Write(uint16_t* buffer,
                   int start,
                   int length,
                   int options) const {
   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 165 matching lines @@
 void v8::Object::SetPointerInInternalField(int index, void* value) {
   i::Isolate* isolate = Utils::OpenHandle(this)->GetIsolate();
   ENTER_V8(isolate);
   if (CanBeEncodedAsSmi(value)) {
     Utils::OpenHandle(this)->SetInternalField(index, EncodeAsSmi(value));
   } else {
     HandleScope scope;
     i::Handle<i::Foreign> foreign =
         isolate->factory()->NewForeign(
             reinterpret_cast<i::Address>(value), i::TENURED);
-    if (!foreign.is_null())
-        Utils::OpenHandle(this)->SetInternalField(index, *foreign);
+    if (!foreign.is_null()) {
+      Utils::OpenHandle(this)->SetInternalField(index, *foreign);
+    }
   }
   ASSERT_EQ(value, GetPointerFromInternalField(index));
 }
 
 
 // --- E n v i r o n m e n t ---
 
 
 bool v8::V8::Initialize() {
   i::Isolate* isolate = i::Isolate::UncheckedCurrent();
@@ skipping 2278 matching lines @@
 
   v->VisitPointers(blocks_.first(), first_block_limit_);
 
   for (int i = 1; i < blocks_.length(); i++) {
     v->VisitPointers(blocks_[i], &blocks_[i][kHandleBlockSize]);
   }
 }
 
 
 } }  // namespace v8::internal