[api] simplify String::WriteToUtf8.

Since we always flatten the string upfront, we don't need to
implement the the UTF8 conversion as a string visitor anymore.

R=petermarshall@chromium.org

Bug: v8:6780, v8:8605
Change-Id: I27946551d7c3742f47ac36d5c909c19a7f2b0371
Reviewed-on: https://chromium-review.googlesource.com/c/1371828
Commit-Queue: Yang Guo <yangguo@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58312}

test/cctest/test-api.cc

@@ -8452,6 +8452,13 @@ THREADED_TEST(StringWrite) {
   int len;
   int charlen;
 
+  memset(utf8buf, 0x1, 1000);
+  len = v8::String::Empty(isolate)->WriteUtf8(isolate, utf8buf, sizeof(utf8buf),
+                                              &charlen);
+  CHECK_EQ(1, len);
+  CHECK_EQ(0, charlen);
+  CHECK_EQ(0, strcmp(utf8buf, ""));
+
   memset(utf8buf, 0x1, 1000);
   len = str2->WriteUtf8(isolate, utf8buf, sizeof(utf8buf), &charlen);
   CHECK_EQ(9, len);

test/cctest/test-strings.cc

@@ -35,6 +35,7 @@
 #include "src/v8.h"
 
 #include "src/api-inl.h"
+#include "src/base/platform/elapsed-timer.h"
 #include "src/heap/factory.h"
 #include "src/messages.h"
 #include "src/objects-inl.h"
@@ -957,6 +958,109 @@ TEST(Utf8Conversion) {
   }
 }
 
+TEST(Utf8ConversionPerf) {
+  // Smoke test for converting strings to utf-8.
+  LocalContext context;
+  v8::HandleScope handle_scope(CcTest::isolate());
+  v8::Local<v8::String> ascii_string =
+      CompileRun("'abc'.repeat(1E6)").As<v8::String>();
+  v8::Local<v8::String> one_byte_string =
+      CompileRun("'\\u0255\\u0254\\u0253'.repeat(1E6)").As<v8::String>();
+  v8::Local<v8::String> two_byte_string =
+      CompileRun("'\\u2255\\u2254\\u2253'.repeat(1E6)").As<v8::String>();
+  v8::Local<v8::String> surrogate_string =
+      CompileRun("'\\u{12345}\\u2244'.repeat(1E6)").As<v8::String>();
+  int size = 1E7;
+  char* buffer = new char[4 * size];
+  {
+    v8::base::ElapsedTimer timer;
+    timer.Start();
+    ascii_string->WriteUtf8(CcTest::isolate(), buffer, size, nullptr);
+    printf("ascii string %0.3f\n", timer.Elapsed().InMillisecondsF());
+    timer.Stop();
+  }
+  {
+    v8::base::ElapsedTimer timer;
+    timer.Start();
+    ascii_string->WriteUtf8(CcTest::isolate(), buffer, size, nullptr);
+    printf("ascii string %0.3f\n", timer.Elapsed().InMillisecondsF());
+    timer.Stop();
+  }
+  {
+    v8::base::ElapsedTimer timer;
+    timer.Start();
+    ascii_string->WriteUtf8(CcTest::isolate(), buffer, 4 * size, nullptr);
+    printf("ascii string %0.3f\n", timer.Elapsed().InMillisecondsF());
+    timer.Stop();
+  }
+
+  {
+    v8::base::ElapsedTimer timer;
+    timer.Start();
+    one_byte_string->WriteUtf8(CcTest::isolate(), buffer, size, nullptr);
+    printf("one byte string %0.3f\n", timer.Elapsed().InMillisecondsF());
+    timer.Stop();
+  }
+  {
+    v8::base::ElapsedTimer timer;
+    timer.Start();
+    one_byte_string->WriteUtf8(CcTest::isolate(), buffer, size, nullptr);
+    printf("one byte string %0.3f\n", timer.Elapsed().InMillisecondsF());
+    timer.Stop();
+  }
+  {
+    v8::base::ElapsedTimer timer;
+    timer.Start();
+    one_byte_string->WriteUtf8(CcTest::isolate(), buffer, 4 * size, nullptr);
+    printf("one byte string %0.3f\n", timer.Elapsed().InMillisecondsF());
+    timer.Stop();
+  }
+
+  {
+    v8::base::ElapsedTimer timer;
+    timer.Start();
+    two_byte_string->WriteUtf8(CcTest::isolate(), buffer, size, nullptr);
+    printf("two byte string %0.3f\n", timer.Elapsed().InMillisecondsF());
+    timer.Stop();
+  }
+  {
+    v8::base::ElapsedTimer timer;
+    timer.Start();
+    two_byte_string->WriteUtf8(CcTest::isolate(), buffer, size, nullptr);
+    printf("two byte string %0.3f\n", timer.Elapsed().InMillisecondsF());
+    timer.Stop();
+  }
+  {
+    v8::base::ElapsedTimer timer;
+    timer.Start();
+    two_byte_string->WriteUtf8(CcTest::isolate(), buffer, 4 * size, nullptr);
+    printf("two byte string %0.3f\n", timer.Elapsed().InMillisecondsF());
+    timer.Stop();
+  }
+
+  {
+    v8::base::ElapsedTimer timer;
+    timer.Start();
+    surrogate_string->WriteUtf8(CcTest::isolate(), buffer, size, nullptr);
+    printf("surrogate string %0.3f\n", timer.Elapsed().InMillisecondsF());
+    timer.Stop();
+  }
+  {
+    v8::base::ElapsedTimer timer;
+    timer.Start();
+    surrogate_string->WriteUtf8(CcTest::isolate(), buffer, size, nullptr);
+    printf("surrogate string %0.3f\n", timer.Elapsed().InMillisecondsF());
+    timer.Stop();
+  }
+  {
+    v8::base::ElapsedTimer timer;
+    timer.Start();
+    surrogate_string->WriteUtf8(CcTest::isolate(), buffer, 4 * size, nullptr);
+    printf("surrogate string %0.3f\n", timer.Elapsed().InMillisecondsF());
+    timer.Stop();
+  }
+  delete[] buffer;
+}
 
 TEST(ExternalShortStringAdd) {
   LocalContext context;
@@ -1064,6 +1168,27 @@ TEST(ExternalShortStringAdd) {
   CHECK_EQ(0, CompileRun(source)->Int32Value(context.local()).FromJust());
 }
 
+TEST(ReplaceInvalidUtf8) {
+  LocalContext context;
+  v8::HandleScope handle_scope(CcTest::isolate());
+  v8::Local<v8::String> string = CompileRun("'ab\\ud800cd'").As<v8::String>();
+  char buffer[7];
+  memset(buffer, 0, 7);
+  int chars_written = 0;
+  int size = string->WriteUtf8(CcTest::isolate(), buffer, 7, &chars_written,
+                               v8::String::REPLACE_INVALID_UTF8);
+  CHECK_EQ(7, size);
+  CHECK_EQ(5, chars_written);
+  CHECK_EQ(0, memcmp("\x61\x62\xef\xbf\xbd\x63\x64", buffer, 7));
+
+  memset(buffer, 0, 7);
+  chars_written = 0;
+  size = string->WriteUtf8(CcTest::isolate(), buffer, 6, &chars_written,
+                           v8::String::REPLACE_INVALID_UTF8);
+  CHECK_EQ(6, size);
+  CHECK_EQ(4, chars_written);
+  CHECK_EQ(0, memcmp("\x61\x62\xef\xbf\xbd\x63", buffer, 6));
+}
 
 TEST(JSONStringifySliceMadeExternal) {
   if (!FLAG_string_slices) return;