LibJS: Add Uint8ClampedArray :^)

This is a special kind of byte array that clamps its values to 0...255
It will be used for HTML ImageData objects.

I made Object::put_by_index() and get_by_index() virtual for this.
We'll probably need to make non-numeric property name lookups virtual
as well, but this solves my current problem well enough.

Libraries/LibJS/Forward.h

@@ -69,6 +69,7 @@ class PrimitiveString;
 class ScopeNode;
 class Shape;
 class Statement;
+class Uint8ClampedArray;
 class Value;
 enum class DeclarationKind;
 

Libraries/LibJS/Makefile

@@ -43,6 +43,7 @@ OBJS = \
     Runtime/StringConstructor.o \
     Runtime/StringObject.o \
     Runtime/StringPrototype.o \
+    Runtime/Uint8ClampedArray.o \
     Runtime/Value.o \
     Token.o
 

Libraries/LibJS/Runtime/Object.h

@@ -46,11 +46,11 @@ public:
     Shape& shape() { return *m_shape; }
     const Shape& shape() const { return *m_shape; }
 
-    Optional<Value> get_by_index(i32 property_index) const;
+    virtual Optional<Value> get_by_index(i32 property_index) const;
     Optional<Value> get(const FlyString& property_name) const;
     Optional<Value> get(PropertyName) const;
 
-    void put_by_index(i32 property_index, Value);
+    virtual void put_by_index(i32 property_index, Value);
     void put(const FlyString& property_name, Value);
     void put(PropertyName, Value);
 

Libraries/LibJS/Runtime/Uint8ClampedArray.cpp

@@ -0,0 +1,82 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <AK/Function.h>
+#include <LibJS/Interpreter.h>
+#include <LibJS/Runtime/Error.h>
+#include <LibJS/Runtime/GlobalObject.h>
+#include <LibJS/Runtime/Uint8ClampedArray.h>
+
+namespace JS {
+
+Uint8ClampedArray* Uint8ClampedArray::create(GlobalObject& global_object, i32 length)
+{
+    ASSERT(length >= 0);
+    auto& interpreter = global_object.interpreter();
+    return interpreter.heap().allocate<Uint8ClampedArray>(length, *global_object.array_prototype());
+}
+
+Uint8ClampedArray::Uint8ClampedArray(i32 length, Object& prototype)
+    : Object(&prototype)
+    , m_length(length)
+{
+    ASSERT(m_length >= 0);
+    put_native_property("length", length_getter, nullptr);
+    m_data = new u8[m_length];
+}
+
+Uint8ClampedArray::~Uint8ClampedArray()
+{
+    ASSERT(m_data);
+    delete[] m_data;
+    m_data = nullptr;
+}
+
+Value Uint8ClampedArray::length_getter(Interpreter& interpreter)
+{
+    auto* this_object = interpreter.this_value().to_object(interpreter.heap());
+    if (!this_object)
+        return {};
+    if (StringView(this_object->class_name()) != "Uint8ClampedArray")
+        return interpreter.throw_exception<TypeError>("Not a Uint8ClampedArray");
+    return Value(static_cast<const Uint8ClampedArray*>(this_object)->length());
+}
+
+void Uint8ClampedArray::put_by_index(i32 property_index, Value value)
+{
+    ASSERT(property_index >= 0);
+    ASSERT(property_index < m_length);
+    m_data[property_index] = clamp(value.to_i32(), 0, 255);
+}
+
+Optional<Value> Uint8ClampedArray::get_by_index(i32 property_index) const
+{
+    ASSERT(property_index >= 0);
+    ASSERT(property_index < m_length);
+    return Value((i32)m_data[property_index]);
+}
+
+}

Libraries/LibJS/Runtime/Uint8ClampedArray.h

@@ -0,0 +1,58 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <LibJS/Runtime/Object.h>
+
+namespace JS {
+
+class Uint8ClampedArray final : public Object {
+public:
+    static Uint8ClampedArray* create(GlobalObject&, i32 length);
+
+    Uint8ClampedArray(i32 length, Object& prototype);
+    virtual ~Uint8ClampedArray() override;
+
+    i32 length() const { return m_length; }
+
+    virtual void put_by_index(i32 property_index, Value value) override;
+    virtual Optional<Value> get_by_index(i32 property_index) const override;
+
+    u8* data() { return m_data; }
+    const u8* data() const { return m_data; }
+
+private:
+    virtual const char* class_name() const override { return "Uint8ClampedArray"; }
+    virtual bool is_array() const override { return true; }
+
+    static Value length_getter(Interpreter&);
+
+    u8* m_data { nullptr };
+    i32 m_length { 0 };
+};
+
+}