`substringSharingImpl` allocates, do not use

2 files changed, 27 insertions, 57 deletions

diff --git a/src/bun.js/bindings/JSBuffer.cpp b/src/bun.js/bindings/JSBuffer.cpp
index c985a7505..a6c735af7 100644
--- a/src/bun.js/bindings/JSBuffer.cpp
+++ b/src/bun.js/bindings/JSBuffer.cpp
@@ -729,7 +729,10 @@ static inline JSC::EncodedJSValue jsBufferConstructorFunction_concatBody(JSC::JS
 static inline JSC::EncodedJSValue jsBufferConstructorFunction_isEncodingBody(JSC::JSGlobalObject* lexicalGlobalObject, JSC::CallFrame* callFrame)
 {
     auto& vm = JSC::getVM(lexicalGlobalObject);
-    auto encoding_ = callFrame->argument(0).toString(lexicalGlobalObject);
+    auto* encoding_ = callFrame->argument(0).toStringOrNull(lexicalGlobalObject);
+    if (!encoding_)
+        return JSValue::encode(jsBoolean(false));
+
     std::optional<BufferEncodingType> encoded = parseEnumeration<BufferEncodingType>(*lexicalGlobalObject, encoding_);
     return JSValue::encode(jsBoolean(!!encoded));
 }
diff --git a/src/bun.js/bindings/JSBufferEncodingType.cpp b/src/bun.js/bindings/JSBufferEncodingType.cpp
index d65e90d2b..8d99dd4db 100644
--- a/src/bun.js/bindings/JSBufferEncodingType.cpp
+++ b/src/bun.js/bindings/JSBufferEncodingType.cpp
@@ -30,19 +30,21 @@
 namespace WebCore {
 using namespace JSC;
 
+static const NeverDestroyed<String> values[] = {
+    MAKE_STATIC_STRING_IMPL("utf8"),
+    MAKE_STATIC_STRING_IMPL("ucs2"),
+    MAKE_STATIC_STRING_IMPL("utf16le"),
+    MAKE_STATIC_STRING_IMPL("latin1"),
+    MAKE_STATIC_STRING_IMPL("ascii"),
+    MAKE_STATIC_STRING_IMPL("base64"),
+    MAKE_STATIC_STRING_IMPL("base64url"),
+    MAKE_STATIC_STRING_IMPL("hex"),
+    MAKE_STATIC_STRING_IMPL("buffer"),
+};
+
 String convertEnumerationToString(BufferEncodingType enumerationValue)
 {
-    static const NeverDestroyed<String> values[] = {
-        MAKE_STATIC_STRING_IMPL("utf8"),
-        MAKE_STATIC_STRING_IMPL("ucs2"),
-        MAKE_STATIC_STRING_IMPL("utf16le"),
-        MAKE_STATIC_STRING_IMPL("latin1"),
-        MAKE_STATIC_STRING_IMPL("ascii"),
-        MAKE_STATIC_STRING_IMPL("base64"),
-        MAKE_STATIC_STRING_IMPL("base64url"),
-        MAKE_STATIC_STRING_IMPL("hex"),
-        MAKE_STATIC_STRING_IMPL("buffer"),
-    };
+
     ASSERT(static_cast<size_t>(enumerationValue) < std::size(values));
     return values[static_cast<size_t>(enumerationValue)];
 }
@@ -55,9 +57,9 @@ template<> JSString* convertEnumerationToJS(JSGlobalObject& lexicalGlobalObject,
 // this function is mostly copied from node
 template<> std::optional<BufferEncodingType> parseEnumeration<BufferEncodingType>(JSGlobalObject& lexicalGlobalObject, JSValue value)
 {
-
-    JSC::JSString* str = value.toStringOrNull(&lexicalGlobalObject);
-    if (!str)
+    // caller must check if value is a string
+    JSC::JSString* str = asString(value);
+    if (UNLIKELY(!str))
         return std::nullopt;
 
     auto encoding = str->value(&lexicalGlobalObject);
@@ -75,21 +77,7 @@ template<> std::optional<BufferEncodingType> parseEnumeration<BufferEncodingType
 
     switch (encoding[0]) {
     case 'u':
-    case 'U':
-        // utf8, utf16le
-        if (encoding[1] == 't' && encoding[2] == 'f') {
-            // Skip `-`
-            const size_t skip = encoding[3] == '-' ? 4 : 3;
-            if (encoding[skip] == '8' && encoding[skip + 1] == '\0')
-                return BufferEncodingType::utf8;
-            if (WTF::equalIgnoringASCIICase(encoding.substringSharingImpl(skip, 5), "16le"_s))
-                return BufferEncodingType::ucs2;
-            // ucs2
-        } else if (encoding[1] == 'c' && encoding[2] == 's') {
-            const size_t skip = encoding[3] == '-' ? 4 : 3;
-            if (encoding[skip] == '2' && encoding[skip + 1] == '\0')
-                return BufferEncodingType::ucs2;
-        }
+    case 'U': {
         if (WTF::equalIgnoringASCIICase(encoding, "utf8"_s))
             return BufferEncodingType::utf8;
         if (WTF::equalIgnoringASCIICase(encoding, "utf-8"_s))
@@ -103,35 +91,17 @@ template<> std::optional<BufferEncodingType> parseEnumeration<BufferEncodingType
         if (WTF::equalIgnoringASCIICase(encoding, "utf-16le"_s))
             return BufferEncodingType::ucs2;
         break;
+    }
 
     case 'l':
-    case 'L':
-        // latin1
-        if (encoding[1] == 'a') {
-            if (WTF::equalIgnoringASCIICase(encoding.substringSharingImpl(2, 4), "tin1"_s))
-                return BufferEncodingType::latin1;
-        }
+    case 'L': {
         if (WTF::equalIgnoringASCIICase(encoding, "latin1"_s))
             return BufferEncodingType::latin1;
         break;
+    }
 
     case 'b':
-    case 'B':
-        // binary is a deprecated alias of latin1
-        if (encoding[1] == 'i') {
-            if (WTF::equalIgnoringASCIICase(encoding.substringSharingImpl(2, 5), "nary"_s))
-                return BufferEncodingType::latin1;
-            // buffer
-        } else if (encoding[1] == 'u') {
-            if (WTF::equalIgnoringASCIICase(encoding.substringSharingImpl(2, 5), "ffer"_s))
-                return BufferEncodingType::buffer;
-            // base64
-        } else if (encoding[1] == 'a') {
-            if (WTF::equalIgnoringASCIICase(encoding.substringSharingImpl(2, 5), "se64"_s))
-                return BufferEncodingType::base64;
-            if (WTF::equalIgnoringASCIICase(encoding.substringSharingImpl(2, 8), "se64url"_s))
-                return BufferEncodingType::base64url;
-        }
+    case 'B': {
         if (WTF::equalIgnoringASCIICase(encoding, "binary"_s))
             return BufferEncodingType::latin1; // BINARY is a deprecated alias of LATIN1.
         if (WTF::equalIgnoringASCIICase(encoding, "buffer"_s))
@@ -141,15 +111,12 @@ template<> std::optional<BufferEncodingType> parseEnumeration<BufferEncodingType
         if (WTF::equalIgnoringASCIICase(encoding, "base64url"_s))
             return BufferEncodingType::base64url;
         break;
+    }
 
     case 'a':
     case 'A':
         // ascii
-        if (encoding[1] == 's') {
-            if (WTF::equalIgnoringASCIICase(encoding.substringSharingImpl(2, 3), "cii"_s))
-                return BufferEncodingType::ascii;
-        }
-        if (WTF::equalIgnoringASCIICase(encoding, "ascii"_s))
+        if (WTF::equalLettersIgnoringASCIICase(encoding, "ascii"_s))
             return BufferEncodingType::ascii;
         break;