Add native StringDecoder (#1188)

* Add native StringDecoder

* fix upon reviews

* add Constructor and use LazyClassStructure

1 files changed, 129 insertions, 0 deletions

diff --git a/src/bun.js/bindings/JSStringDecoder.h b/src/bun.js/bindings/JSStringDecoder.h
new file mode 100644
index 000000000..de2c54209
--- /dev/null
+++ b/src/bun.js/bindings/JSStringDecoder.h
@@ -0,0 +1,129 @@
+#pragma once
+
+#include "root.h"
+#include "BufferEncodingType.h"
+
+namespace WebCore {
+using namespace JSC;
+
+class JSStringDecoder : public JSC::JSDestructibleObject {
+    using Base = JSC::JSDestructibleObject;
+
+public:
+    JSStringDecoder(JSC::VM& vm, JSC::Structure* structure, BufferEncodingType encoding)
+        : Base(vm, structure), m_lastNeed(0), m_lastTotal(0), m_encoding(encoding)
+    {
+    }
+
+    DECLARE_INFO;
+
+    static constexpr unsigned StructureFlags = Base::StructureFlags;
+
+    template<typename, JSC::SubspaceAccess mode> static JSC::GCClient::IsoSubspace* subspaceFor(JSC::VM& vm)
+    {
+        if constexpr (mode == JSC::SubspaceAccess::Concurrently)
+            return nullptr;
+        return subspaceForImpl(vm);
+    }
+
+    static JSC::GCClient::IsoSubspace* subspaceForImpl(JSC::VM& vm);
+
+    static JSC::Structure* createStructure(JSC::VM& vm, JSC::JSGlobalObject* globalObject,
+        JSC::JSValue prototype)
+    {
+        return JSC::Structure::create(vm, globalObject, prototype,
+            JSC::TypeInfo(JSC::ObjectType, StructureFlags), info());
+    }
+
+    static JSStringDecoder* create(JSC::VM& vm, JSC::JSGlobalObject* globalObject, JSC::Structure* structure, BufferEncodingType encoding)
+    {
+        JSStringDecoder* accessor = new (NotNull, JSC::allocateCell<JSStringDecoder>(vm)) JSStringDecoder(vm, structure, encoding);
+        accessor->finishCreation(vm, globalObject);
+        return accessor;
+    }
+
+    void finishCreation(JSC::VM& vm, JSC::JSGlobalObject* globalObject);
+    static void destroy(JSCell*) {}
+
+    JSC::JSValue write(JSC::VM&, JSC::JSGlobalObject*, uint8_t*, uint32_t);
+    JSC::JSValue end(JSC::VM&, JSC::JSGlobalObject*, uint8_t*, uint32_t);
+
+    uint8_t m_lastNeed;
+    uint8_t m_lastTotal;
+    uint8_t m_lastChar[4];
+
+private:
+    JSC::JSValue fillLast(JSC::VM&, JSC::JSGlobalObject*, uint8_t*, uint32_t);
+    JSC::JSValue text(JSC::VM&, JSC::JSGlobalObject*, uint8_t*, uint32_t, uint32_t);
+    uint8_t utf8CheckIncomplete(uint8_t*, uint32_t, uint32_t);
+
+    BufferEncodingType m_encoding;
+};
+
+class JSStringDecoderPrototype : public JSC::JSNonFinalObject {
+public:
+    using Base = JSC::JSNonFinalObject;
+    static JSStringDecoderPrototype* create(JSC::VM& vm, JSC::JSGlobalObject* globalObject, JSC::Structure* structure)
+    {
+        JSStringDecoderPrototype* ptr = new (NotNull, JSC::allocateCell<JSStringDecoderPrototype>(vm)) JSStringDecoderPrototype(vm, structure);
+        ptr->finishCreation(vm, globalObject);
+        return ptr;
+    }
+
+    DECLARE_INFO;
+    template<typename CellType, JSC::SubspaceAccess>
+    static JSC::GCClient::IsoSubspace* subspaceFor(JSC::VM& vm)
+    {
+        return &vm.plainObjectSpace();
+    }
+    static JSC::Structure* createStructure(JSC::VM& vm, JSC::JSGlobalObject* globalObject, JSC::JSValue prototype)
+    {
+        return JSC::Structure::create(vm, globalObject, prototype, JSC::TypeInfo(JSC::ObjectType, StructureFlags), info());
+    }
+
+private:
+    JSStringDecoderPrototype(JSC::VM& vm, JSC::Structure* structure)
+        : Base(vm, structure)
+    {
+    }
+
+    void finishCreation(JSC::VM&, JSC::JSGlobalObject*);
+};
+
+class JSStringDecoderConstructor final : public JSC::InternalFunction {
+public:
+    using Base = JSC::InternalFunction;
+    static JSStringDecoderConstructor* create(JSC::VM& vm, JSC::JSGlobalObject* globalObject, JSC::Structure* structure, JSStringDecoderPrototype* prototype);
+
+    static constexpr unsigned StructureFlags = Base::StructureFlags;
+    static constexpr bool needsDestruction = false;
+
+    static JSC::Structure* createStructure(JSC::VM& vm, JSC::JSGlobalObject* globalObject, JSC::JSValue prototype)
+    {
+        return JSC::Structure::create(vm, globalObject, prototype, JSC::TypeInfo(JSC::InternalFunctionType, StructureFlags), info());
+    }
+
+    template<typename, JSC::SubspaceAccess mode> static JSC::GCClient::IsoSubspace* subspaceFor(JSC::VM& vm)
+    {
+        if constexpr (mode == JSC::SubspaceAccess::Concurrently)
+            return nullptr;
+        return subspaceForImpl(vm);
+    }
+
+    static JSC::GCClient::IsoSubspace* subspaceForImpl(JSC::VM& vm);
+
+    void initializeProperties(JSC::VM& vm, JSC::JSGlobalObject* globalObject, JSStringDecoderPrototype* prototype);
+
+    // Must be defined for each specialization class.
+    static JSC::EncodedJSValue JSC_HOST_CALL_ATTRIBUTES construct(JSC::JSGlobalObject*, JSC::CallFrame*);
+    DECLARE_EXPORT_INFO;
+private:
+    JSStringDecoderConstructor(JSC::VM& vm, JSC::Structure* structure, JSC::NativeFunction nativeFunction)
+        : Base(vm, structure, nativeFunction, nativeFunction)
+    {
+    }
+
+    void finishCreation(JSC::VM&, JSC::JSGlobalObject* globalObject, JSStringDecoderPrototype* prototype);
+};
+
+}