From 5131e66fa5dece8ca99093dc5573e22ca8b5d682 Mon Sep 17 00:00:00 2001
From: Jarred Sumner <jarred@jarredsumner.com>
Date: Tue, 24 Jun 2025 17:39:33 -0700
Subject: [PATCH] Optimize  `napi_get_value_string_utf8`
 `napi_get_value_string_latin1`  `napi_get_value_string_utf16` (#20612)

---
 src/bun.js/bindings/napi.cpp | 28 +++++++++++++++++-----------
 1 file changed, 17 insertions(+), 11 deletions(-)

diff --git a/src/bun.js/bindings/napi.cpp b/src/bun.js/bindings/napi.cpp
index 3d5f0340ed..fcbe5c986f 100644
--- a/src/bun.js/bindings/napi.cpp
+++ b/src/bun.js/bindings/napi.cpp
@@ -2059,23 +2059,26 @@ struct BufferElement<NapiStringEncoding::utf16le> {
 template<NapiStringEncoding EncodeTo>
 napi_status napi_get_value_string_any_encoding(napi_env env, napi_value napiValue, typename BufferElement<EncodeTo>::Type* buf, size_t bufsize, size_t* writtenPtr)
 {
+    NAPI_PREAMBLE(env);
     NAPI_CHECK_ARG(env, napiValue);
     JSValue jsValue = toJS(napiValue);
     NAPI_RETURN_EARLY_IF_FALSE(env, jsValue.isString(), napi_string_expected);
 
     Zig::GlobalObject* globalObject = toJS(env);
-    String view = jsValue.asCell()->getString(globalObject);
-    size_t length = view.length();
+    JSString* jsString = jsValue.toString(globalObject);
+    NAPI_RETURN_IF_EXCEPTION(env);
+    const auto view = jsString->view(globalObject);
+    NAPI_RETURN_IF_EXCEPTION(env);
 
     if (buf == nullptr) {
         // they just want to know the length
         NAPI_CHECK_ARG(env, writtenPtr);
         switch (EncodeTo) {
         case NapiStringEncoding::utf8:
-            if (view.is8Bit()) {
-                *writtenPtr = Bun__encoding__byteLengthLatin1AsUTF8(view.span8().data(), length);
+            if (view->is8Bit()) {
+                *writtenPtr = Bun__encoding__byteLengthLatin1AsUTF8(view->span8().data(), view->length());
             } else {
-                *writtenPtr = Bun__encoding__byteLengthUTF16AsUTF8(view.span16().data(), length);
+                *writtenPtr = Bun__encoding__byteLengthUTF16AsUTF8(view->span16().data(), view->length());
             }
             break;
         case NapiStringEncoding::utf16le:
@@ -2084,7 +2087,7 @@ napi_status napi_get_value_string_any_encoding(napi_env env, napi_value napiValu
             // if the string's encoding is the same as the destination encoding, this is trivially correct
             // if we are converting UTF-16 to Latin-1, then we do so by truncating each code unit, so the length is the same
             // if we are converting Latin-1 to UTF-16, then we do so by extending each code unit, so the length is also the same
-            *writtenPtr = length;
+            *writtenPtr = view->length();
             break;
         }
         return napi_set_last_error(env, napi_ok);
@@ -2108,19 +2111,22 @@ napi_status napi_get_value_string_any_encoding(napi_env env, napi_value napiValu
             // since we need to put a null terminator there
             ? 2 * (bufsize - 1)
             : bufsize - 1);
-    if (view.is8Bit()) {
+    if (view->is8Bit()) {
+        const auto span = view->span8();
         if constexpr (EncodeTo == NapiStringEncoding::utf16le) {
+
             // pass subslice to work around Bun__encoding__writeLatin1 asserting that the output has room
-            written = Bun__encoding__writeLatin1(view.span8().data(),
-                std::min(static_cast<size_t>(view.span8().size()), bufsize),
+            written = Bun__encoding__writeLatin1(span.data(),
+                std::min(static_cast<size_t>(span.size()), bufsize),
                 writable_byte_slice.data(),
                 writable_byte_slice.size(),
                 static_cast<uint8_t>(EncodeTo));
         } else {
-            written = Bun__encoding__writeLatin1(view.span8().data(), view.length(), writable_byte_slice.data(), writable_byte_slice.size(), static_cast<uint8_t>(EncodeTo));
+            written = Bun__encoding__writeLatin1(span.data(), span.size(), writable_byte_slice.data(), writable_byte_slice.size(), static_cast<uint8_t>(EncodeTo));
         }
     } else {
-        written = Bun__encoding__writeUTF16(view.span16().data(), view.length(), writable_byte_slice.data(), writable_byte_slice.size(), static_cast<uint8_t>(EncodeTo));
+        const auto span = view->span16();
+        written = Bun__encoding__writeUTF16(span.data(), span.size(), writable_byte_slice.data(), writable_byte_slice.size(), static_cast<uint8_t>(EncodeTo));
     }
 
     // convert bytes to code units