From f4ea6b182404e510d05ebd1e36c4160660d1ef1a Mon Sep 17 00:00:00 2001
From: Timothy Flynn <trflynn89@pm.me>
Date: Sun, 11 Jul 2021 08:57:54 -0400
Subject: LibJS: Implement TypedArray GetModifySetValueInBuffer abstract
 operation

---
 Userland/Libraries/LibJS/Runtime/ArrayBuffer.h | 21 +++++++++++++++++++++
 Userland/Libraries/LibJS/Runtime/TypedArray.h  |  3 +++
 2 files changed, 24 insertions(+)

(limited to 'Userland/Libraries')

diff --git a/Userland/Libraries/LibJS/Runtime/ArrayBuffer.h b/Userland/Libraries/LibJS/Runtime/ArrayBuffer.h
index 4d712e56f4..681f363190 100644
--- a/Userland/Libraries/LibJS/Runtime/ArrayBuffer.h
+++ b/Userland/Libraries/LibJS/Runtime/ArrayBuffer.h
@@ -7,6 +7,7 @@
 #pragma once
 
 #include <AK/ByteBuffer.h>
+#include <AK/Function.h>
 #include <AK/Variant.h>
 #include <LibJS/Runtime/GlobalObject.h>
 #include <LibJS/Runtime/Object.h>
@@ -16,6 +17,9 @@ namespace JS {
 struct ClampedU8 {
 };
 
+// 25.1.1 Notation (read-modify-write modification function), https://tc39.es/ecma262/#sec-arraybuffer-notation
+using ReadWriteModifyFunction = Function<ByteBuffer(ByteBuffer, ByteBuffer)>;
+
 class ArrayBuffer : public Object {
     JS_OBJECT(ArrayBuffer, Object);
 
@@ -45,6 +49,8 @@ public:
     Value get_value(size_t byte_index, bool is_typed_array, Order, bool is_little_endian = true);
     template<typename type>
     Value set_value(size_t byte_index, Value value, bool is_typed_array, Order, bool is_little_endian = true);
+    template<typename T>
+    Value get_modify_set_value(size_t byte_index, Value value, ReadWriteModifyFunction operation, bool is_little_endian = true);
 
 private:
     virtual void visit_edges(Visitor&) override;
@@ -190,4 +196,19 @@ Value ArrayBuffer::set_value(size_t byte_index, Value value, [[maybe_unused]] bo
     return js_undefined();
 }
 
+// 25.1.2.13 GetModifySetValueInBuffer ( arrayBuffer, byteIndex, type, value, op [ , isLittleEndian ] ), https://tc39.es/ecma262/#sec-getmodifysetvalueinbuffer
+template<typename T>
+Value ArrayBuffer::get_modify_set_value(size_t byte_index, Value value, ReadWriteModifyFunction operation, bool is_little_endian)
+{
+    auto raw_bytes = numeric_to_raw_bytes<T>(global_object(), value, is_little_endian);
+
+    // FIXME: Check for shared buffer
+
+    auto raw_bytes_read = buffer_impl().slice(byte_index, sizeof(T));
+    auto raw_bytes_modified = operation(raw_bytes_read, raw_bytes);
+    raw_bytes_modified.span().copy_to(buffer_impl().span().slice(byte_index));
+
+    return raw_bytes_to_numeric<T>(global_object(), raw_bytes_read, is_little_endian);
+}
+
 }
diff --git a/Userland/Libraries/LibJS/Runtime/TypedArray.h b/Userland/Libraries/LibJS/Runtime/TypedArray.h
index 83d40f6cc7..fb501170e1 100644
--- a/Userland/Libraries/LibJS/Runtime/TypedArray.h
+++ b/Userland/Libraries/LibJS/Runtime/TypedArray.h
@@ -44,6 +44,8 @@ public:
     virtual Value get_value_from_buffer(size_t byte_index, ArrayBuffer::Order, bool is_little_endian = true) const = 0;
     // 25.1.2.12 SetValueInBuffer ( arrayBuffer, byteIndex, type, value, isTypedArray, order [ , isLittleEndian ] ), https://tc39.es/ecma262/#sec-setvalueinbuffer
     virtual void set_value_in_buffer(size_t byte_index, Value, ArrayBuffer::Order, bool is_little_endian = true) = 0;
+    // 25.1.2.13 GetModifySetValueInBuffer ( arrayBuffer, byteIndex, type, value, op [ , isLittleEndian ] ), https://tc39.es/ecma262/#sec-getmodifysetvalueinbuffer
+    virtual Value get_modify_set_value_in_buffer(size_t byte_index, Value value, ReadWriteModifyFunction operation, bool is_little_endian = true) = 0;
 
 protected:
     explicit TypedArrayBase(Object& prototype)
@@ -438,6 +440,7 @@ public:
 
     Value get_value_from_buffer(size_t byte_index, ArrayBuffer::Order order, bool is_little_endian = true) const override { return viewed_array_buffer()->template get_value<T>(byte_index, true, order, is_little_endian); }
     void set_value_in_buffer(size_t byte_index, Value value, ArrayBuffer::Order order, bool is_little_endian = true) override { viewed_array_buffer()->template set_value<T>(byte_index, value, true, order, is_little_endian); }
+    Value get_modify_set_value_in_buffer(size_t byte_index, Value value, ReadWriteModifyFunction operation, bool is_little_endian = true) override { return viewed_array_buffer()->template get_modify_set_value<T>(byte_index, value, move(operation), is_little_endian); }
 
 protected:
     TypedArray(u32 array_length, Object& prototype)
-- 
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