VM: Speed up output of UTF8 for 1-byte strings.

runtime/vm/object.cc

Index: runtime/vm/object.cc
diff --git a/runtime/vm/object.cc b/runtime/vm/object.cc
index cfd08f6c964c7df53dd6dcd9cfd761f14f4b44e4..e97eccc5442aeece7bf153c0c1de817b383259dc 100644
--- a/runtime/vm/object.cc
+++ b/runtime/vm/object.cc
@@ -19857,14 +19857,14 @@ RawString* String::FromUTF8(const uint8_t* utf8_array,
     if (len > 0) {
       NoSafepointScope no_safepoint;
       Utf8::DecodeToLatin1(utf8_array, array_len,
-                           OneByteString::CharAddr(strobj, 0), len);
+                           OneByteString::DataStart(strobj), len);
     }
     return strobj.raw();
   }
   ASSERT((type == Utf8::kBMP) || (type == Utf8::kSupplementary));
   const String& strobj = String::Handle(TwoByteString::New(len, space));
   NoSafepointScope no_safepoint;
-  Utf8::DecodeToUTF16(utf8_array, array_len, TwoByteString::CharAddr(strobj, 0),
+  Utf8::DecodeToUTF16(utf8_array, array_len, TwoByteString::DataStart(strobj),
                       len);
   return strobj.raw();
 }
@@ -20301,29 +20301,6 @@ RawString* String::SubString(Thread* thread,
 }
 
 const char* String::ToCString() const {
-  if (IsOneByteString()) {
-    // Quick conversion if OneByteString contains only ASCII characters.
-    intptr_t len = Length();
-    if (len == 0) {
-      return "";
-    }
-    Zone* zone = Thread::Current()->zone();
-    uint8_t* result = zone->Alloc<uint8_t>(len + 1);
-    NoSafepointScope no_safepoint;
-    const uint8_t* original_str = OneByteString::CharAddr(*this, 0);
-    for (intptr_t i = 0; i < len; i++) {
-      if (original_str[i] <= Utf8::kMaxOneByteChar) {
-        result[i] = original_str[i];
-      } else {
-        len = -1;
-        break;
-      }
-    }
-    if (len > 0) {
-      result[len] = 0;
-      return reinterpret_cast<const char*>(result);
-    }
-  }
   const intptr_t len = Utf8::Length(*this);
   Zone* zone = Thread::Current()->zone();
   uint8_t* result = zone->Alloc<uint8_t>(len + 1);
@@ -20333,25 +20310,6 @@ const char* String::ToCString() const {
 }
 
 char* String::ToMallocCString() const {
-  if (IsOneByteString()) {
-    // Quick conversion if OneByteString contains only ASCII characters.
-    intptr_t len = Length();
-    uint8_t* result = reinterpret_cast<uint8_t*>(malloc(len + 1));
-    NoSafepointScope no_safepoint;
-    const uint8_t* original_str = OneByteString::CharAddr(*this, 0);
-    for (intptr_t i = 0; i < len; i++) {
-      if (original_str[i] <= Utf8::kMaxOneByteChar) {
-        result[i] = original_str[i];
-      } else {
-        len = -1;
-        break;
-      }
-    }
-    if (len > 0) {
-      result[len] = 0;
-      return reinterpret_cast<char*>(result);
-    }
-  }
   const intptr_t len = Utf8::Length(*this);
   uint8_t* result = reinterpret_cast<uint8_t*>(malloc(len + 1));
   ToUTF8(result, len);
@@ -20646,7 +20604,7 @@ RawOneByteString* OneByteString::New(const uint8_t* characters,
   const String& result = String::Handle(OneByteString::New(len, space));
   if (len > 0) {
     NoSafepointScope no_safepoint;
-    memmove(CharAddr(result, 0), characters, len);
+    memmove(DataStart(result), characters, len);
   }
   return OneByteString::raw(result);
 }
@@ -20690,7 +20648,7 @@ RawOneByteString* OneByteString::New(const String& other_one_byte_string,
   ASSERT(other_one_byte_string.IsOneByteString());
   if (other_len > 0) {
     NoSafepointScope no_safepoint;
-    memmove(OneByteString::CharAddr(result, 0),
+    memmove(OneByteString::DataStart(result),
             OneByteString::CharAddr(other_one_byte_string, other_start_index),
             other_len);
   }
@@ -20705,7 +20663,7 @@ RawOneByteString* OneByteString::New(const TypedData& other_typed_data,
   ASSERT(other_typed_data.ElementSizeInBytes() == 1);
   if (other_len > 0) {
     NoSafepointScope no_safepoint;
-    memmove(OneByteString::CharAddr(result, 0),
+    memmove(OneByteString::DataStart(result),
             other_typed_data.DataAddr(other_start_index), other_len);
   }
   return OneByteString::raw(result);
@@ -20719,7 +20677,7 @@ RawOneByteString* OneByteString::New(const ExternalTypedData& other_typed_data,
   ASSERT(other_typed_data.ElementSizeInBytes() == 1);
   if (other_len > 0) {
     NoSafepointScope no_safepoint;
-    memmove(OneByteString::CharAddr(result, 0),
+    memmove(OneByteString::DataStart(result),
             other_typed_data.DataAddr(other_start_index), other_len);
   }
   return OneByteString::raw(result);
@@ -20869,7 +20827,7 @@ RawTwoByteString* TwoByteString::New(const uint16_t* utf16_array,
   const String& result = String::Handle(TwoByteString::New(array_len, space));
   {
     NoSafepointScope no_safepoint;
-    memmove(CharAddr(result, 0), utf16_array, (array_len * 2));
+    memmove(DataStart(result), utf16_array, (array_len * 2));
   }
   return TwoByteString::raw(result);
 }
@@ -20912,7 +20870,7 @@ RawTwoByteString* TwoByteString::New(const TypedData& other_typed_data,
   const String& result = String::Handle(TwoByteString::New(other_len, space));
   if (other_len > 0) {
     NoSafepointScope no_safepoint;
-    memmove(TwoByteString::CharAddr(result, 0),
+    memmove(TwoByteString::DataStart(result),
             other_typed_data.DataAddr(other_start_index),
             other_len * sizeof(uint16_t));
   }
@@ -20926,7 +20884,7 @@ RawTwoByteString* TwoByteString::New(const ExternalTypedData& other_typed_data,
   const String& result = String::Handle(TwoByteString::New(other_len, space));
   if (other_len > 0) {
     NoSafepointScope no_safepoint;
-    memmove(TwoByteString::CharAddr(result, 0),
+    memmove(TwoByteString::DataStart(result),
             other_typed_data.DataAddr(other_start_index),
             other_len * sizeof(uint16_t));
   }