util/{Const,Writable}Buffer: add operator==(nullptr_t)

src/util/AllocatedArray.hxx

@@ -100,6 +100,14 @@ public:
 		return buffer.IsNull();
 	}
 
+	constexpr bool operator==(std::nullptr_t) const {
+		return buffer == nullptr;
+	}
+
+	constexpr bool operator!=(std::nullptr_t) const {
+		return buffer != nullptr;
+	}
+
 	/**
 	 * Returns true if no memory was allocated so far.
 	 */

src/util/ConstBuffer.hxx

@@ -76,6 +76,14 @@ struct ConstBuffer<void> {
 		return data == nullptr;
 	}
 
+	constexpr bool operator==(std::nullptr_t) const {
+		return data == nullptr;
+	}
+
+	constexpr bool operator!=(std::nullptr_t) const {
+		return data != nullptr;
+	}
+
 	constexpr bool IsEmpty() const {
 		return size == 0;
 	}
@@ -143,6 +151,14 @@ struct ConstBuffer {
 		return data == nullptr;
 	}
 
+	constexpr bool operator==(std::nullptr_t) const {
+		return data == nullptr;
+	}
+
+	constexpr bool operator!=(std::nullptr_t) const {
+		return data != nullptr;
+	}
+
 	constexpr bool IsEmpty() const {
 		return size == 0;
 	}

src/util/WritableBuffer.hxx

@@ -68,6 +68,14 @@ struct WritableBuffer<void> {
 		return data == nullptr;
 	}
 
+	constexpr bool operator==(std::nullptr_t) const {
+		return data == nullptr;
+	}
+
+	constexpr bool operator!=(std::nullptr_t) const {
+		return data != nullptr;
+	}
+
 	constexpr bool IsEmpty() const {
 		return size == 0;
 	}
@@ -137,6 +145,14 @@ struct WritableBuffer {
 		return data == nullptr;
 	}
 
+	constexpr bool operator==(std::nullptr_t) const {
+		return data == nullptr;
+	}
+
+	constexpr bool operator!=(std::nullptr_t) const {
+		return data != nullptr;
+	}
+
 	constexpr bool IsEmpty() const {
 		return size == 0;
 	}