Add createFromUtf16 JSI method

packages/react-native/ReactCommon/jsi/jsi/decorator.h

@@ -182,6 +182,10 @@ class RuntimeDecorator : public Base, private jsi::Instrumentation {
   PropNameID createPropNameIDFromString(const String& str) override {
     return plain_.createPropNameIDFromString(str);
   };
+  PropNameID createPropNameIDFromUtf16(const char16_t* utf16, size_t length)
+      override {
+    return plain_.createPropNameIDFromUtf16(utf16, length);
+  }
   PropNameID createPropNameIDFromSymbol(const Symbol& sym) override {
     return plain_.createPropNameIDFromSymbol(sym);
   };
@@ -221,6 +225,9 @@ class RuntimeDecorator : public Base, private jsi::Instrumentation {
   String createStringFromUtf8(const uint8_t* utf8, size_t length) override {
     return plain_.createStringFromUtf8(utf8, length);
   };
+  String createStringFromUtf16(const char16_t* utf16, size_t length) override {
+    return plain_.createStringFromUtf16(utf16, length);
+  }
   std::string utf8(const String& s) override {
     return plain_.utf8(s);
   }
@@ -649,6 +656,11 @@ class WithRuntimeDecorator : public RuntimeDecorator<Plain, Base> {
     Around around{with_};
     return RD::createPropNameIDFromUtf8(utf8, length);
   };
+  PropNameID createPropNameIDFromUtf16(const char16_t* utf16, size_t length)
+      override {
+    Around around{with_};
+    return RD::createPropNameIDFromUtf16(utf16, length);
+  }
   PropNameID createPropNameIDFromString(const String& str) override {
     Around around{with_};
     return RD::createPropNameIDFromString(str);
@@ -704,6 +716,10 @@ class WithRuntimeDecorator : public RuntimeDecorator<Plain, Base> {
     Around around{with_};
     return RD::createStringFromUtf8(utf8, length);
   };
+  String createStringFromUtf16(const char16_t* utf16, size_t length) override {
+    Around around{with_};
+    return RD::createStringFromUtf16(utf16, length);
+  }
   std::string utf8(const String& s) override {
     Around around{with_};
     return RD::utf8(s);

packages/react-native/ReactCommon/jsi/jsi/jsi.cpp

@@ -163,6 +163,49 @@ std::u16string convertUTF8ToUTF16(const std::string& utf8) {
   return ret;
 }
 
+// Given a unsigned number, which is less than 16, return the hex character.
+char hexDigit(unsigned int x) {
+  return x < 10 ? '0' + x : 'A' + (x - 10);
+}
+
+// Given a sequence of UTF 16 code units, return true if all code units are
+// ASCII characters
+bool isAllASCII(const char16_t* utf16, size_t length) {
+  auto* curr = utf16;
+  auto* end = curr + length;
+  for (; curr < end; ++curr) {
+    if (*curr > 0x7F)
+      return false;
+  }
+  return true;
+}
+
+// Given a sequences of UTF 16 code units, return a string that explicitly
+// expresses the code units
+std::string getUtf16CodeUnitString(const char16_t* utf16, size_t length) {
+  std::string s;
+  // Every character will need the character escape "\u" + 4 hex digits. Plus 2
+  // character for the opening and closing single quote.
+  s.reserve(6 * length + 2);
+  s.append("'");
+
+  auto* curr = utf16;
+  auto* end = curr + length;
+  for (; curr < end; ++curr) {
+    s.append("\\u");
+    char16_t ch = *curr;
+    char buffer[4];
+
+    buffer[0] = hexDigit((ch & 0xf000) >> 12);
+    buffer[1] = hexDigit((ch & 0x0f00) >> 8);
+    buffer[2] = hexDigit((ch & 0x00f0) >> 4);
+    buffer[3] = hexDigit(ch & 0x000f);
+    s.append(buffer, 4);
+  }
+  s.append("'");
+  return s;
+}
+
 } // namespace
 
 Buffer::~Buffer() = default;
@@ -248,6 +291,34 @@ Value Runtime::createValueFromJsonUtf8(const uint8_t* json, size_t length) {
   return parseJson.call(*this, String::createFromUtf8(*this, json, length));
 }
 
+String Runtime::createStringFromUtf16(const char16_t* utf16, size_t length) {
+  if (isAllASCII(utf16, length)) {
+    std::string buffer(utf16, utf16 + length);
+    return createStringFromAscii(buffer.data(), length);
+  }
+  auto s = getUtf16CodeUnitString(utf16, length);
+  return global()
+      .getPropertyAsFunction(*this, "eval")
+      .call(*this, s)
+      .getString(*this);
+}
+
+PropNameID Runtime::createPropNameIDFromUtf16(
+    const char16_t* utf16,
+    size_t length) {
+  if (isAllASCII(utf16, length)) {
+    std::string buffer(utf16, utf16 + length);
+    auto jsString = createStringFromAscii(buffer.data(), length);
+    return createPropNameIDFromString(jsString);
+  }
+  auto s = getUtf16CodeUnitString(utf16, length);
+  auto jsString = global()
+                      .getPropertyAsFunction(*this, "eval")
+                      .call(*this, s)
+                      .getString(*this);
+  return createPropNameIDFromString(jsString);
+}
+
 std::u16string Runtime::utf16(const PropNameID& sym) {
   auto utf8Str = utf8(sym);
   return convertUTF8ToUTF16(utf8Str);

packages/react-native/ReactCommon/jsi/jsi/jsi.h

@@ -306,6 +306,9 @@ class JSI_EXPORT Runtime {
   virtual PropNameID createPropNameIDFromUtf8(
       const uint8_t* utf8,
       size_t length) = 0;
+  virtual PropNameID createPropNameIDFromUtf16(
+      const char16_t* utf16,
+      size_t length);
   virtual PropNameID createPropNameIDFromString(const String& str) = 0;
   virtual PropNameID createPropNameIDFromSymbol(const Symbol& sym) = 0;
   virtual std::string utf8(const PropNameID&) = 0;
@@ -322,6 +325,7 @@ class JSI_EXPORT Runtime {
 
   virtual String createStringFromAscii(const char* str, size_t length) = 0;
   virtual String createStringFromUtf8(const uint8_t* utf8, size_t length) = 0;
+  virtual String createStringFromUtf16(const char16_t* utf16, size_t length);
   virtual std::string utf8(const String&) = 0;
 
   // \return a \c Value created from a utf8-encoded JSON string. The default
@@ -515,6 +519,21 @@ class JSI_EXPORT PropNameID : public Pointer {
         reinterpret_cast<const uint8_t*>(utf8.data()), utf8.size());
   }
 
+  /// Given a series of UTF-16 encoded code units, create a PropNameId. The
+  /// input may contain unpaired surrogates, which will be interpreted as a code
+  /// point of the same value.
+  static PropNameID
+  forUtf16(Runtime& runtime, const char16_t* utf16, size_t length) {
+    return runtime.createPropNameIDFromUtf16(utf16, length);
+  }
+
+  /// Given a series of UTF-16 encoded code units stored inside std::u16string,
+  /// create a PropNameId.  The input may contain unpaired surrogates, which
+  /// will be interpreted as a code point of the same value.
+  static PropNameID forUtf16(Runtime& runtime, const std::u16string& str) {
+    return runtime.createPropNameIDFromUtf16(str.data(), str.size());
+  }
+
   /// Create a PropNameID from a JS string.
   static PropNameID forString(Runtime& runtime, const jsi::String& str) {
     return runtime.createPropNameIDFromString(str);
@@ -699,6 +718,21 @@ class JSI_EXPORT String : public Pointer {
         reinterpret_cast<const uint8_t*>(utf8.data()), utf8.length());
   }
 
+  /// Given a series of UTF-16 encoded code units, create a JS String. The input
+  /// may contain unpaired surrogates, which will be interpreted as a code point
+  /// of the same value.
+  static String
+  createFromUtf16(Runtime& runtime, const char16_t* utf16, size_t length) {
+    return runtime.createStringFromUtf16(utf16, length);
+  }
+
+  /// Given a series of UTF-16 encoded code units stored inside std::u16string,
+  /// create a JS String. The input may contain unpaired surrogates, which will
+  /// be interpreted as a code point of the same value.
+  static String createFromUtf16(Runtime& runtime, const std::u16string& utf16) {
+    return runtime.createStringFromUtf16(utf16.data(), utf16.length());
+  }
+
   /// \return whether a and b contain the same characters.
   static bool strictEquals(Runtime& runtime, const String& a, const String& b) {
     return runtime.strictEquals(a, b);

packages/react-native/ReactCommon/jsi/jsi/test/testlib.cpp

@@ -1723,6 +1723,49 @@ TEST_P(JSITest, ObjectCreateWithPrototype) {
   EXPECT_TRUE(child.getPrototype(rd).isNull());
 }
 
+TEST_P(JSITest, CreateFromUtf16Test) {
+  // This Runtime Decorator is used to test the default createStringFromUtf16
+  // and createPropNameIDFromUtf16 implementation for VMs that do not provide
+  // their own implementation
+  class RD : public RuntimeDecorator<Runtime, Runtime> {
+   public:
+    RD(Runtime& rt) : RuntimeDecorator(rt) {}
+
+    String createStringFromUtf16(const char16_t* utf16, size_t length)
+        override {
+      return Runtime::createStringFromUtf16(utf16, length);
+    }
+
+    PropNameID createPropNameIDFromUtf16(const char16_t* utf16, size_t length)
+        override {
+      return Runtime::createPropNameIDFromUtf16(utf16, length);
+    }
+  };
+
+  RD rd = RD(rt);
+  std::u16string utf16 = u"foobar";
+
+  auto jsString = String::createFromUtf16(rd, utf16);
+  EXPECT_EQ(jsString.utf16(rd), utf16);
+  auto prop = PropNameID::forUtf16(rd, utf16);
+  EXPECT_EQ(prop.utf16(rd), utf16);
+
+  utf16 = u"hello!👋";
+  jsString = String::createFromUtf16(rd, utf16.data(), utf16.length());
+  EXPECT_EQ(jsString.utf16(rd), utf16);
+  prop = PropNameID::forUtf16(rd, utf16);
+  EXPECT_EQ(prop.utf16(rd), utf16);
+
+  utf16 = u"\xd83d";
+  jsString = String::createFromUtf16(rd, utf16.data(), utf16.length());
+  /// We need to use charCodeAt instead of UTF16 because the default
+  /// implementation of UTF16 converts to UTF8, then to UTF16, so we will lose
+  /// the lone surrogate value.
+  rd.global().setProperty(rd, "loneSurrogate", jsString);
+  auto cp = eval("loneSurrogate.charCodeAt(0)").getNumber();
+  EXPECT_EQ(cp, 55357); // 0xD83D in decimal
+}
+
 INSTANTIATE_TEST_CASE_P(
     Runtimes,
     JSITest,