LibPDF: Create basic object structure

This commit is the start of LibPDF, and introduces some basic structure
objects. This emulates LibJS's Value structure, where Value is a simple
class that can contain a pointer to a more complex Object class with
more data. All of the basic PDF objects have a representation.

1 files changed, 134 insertions, 0 deletions

diff --git a/Userland/Libraries/LibPDF/Value.h b/Userland/Libraries/LibPDF/Value.h
new file mode 100644
index 0000000000..6999902bfc
--- /dev/null
+++ b/Userland/Libraries/LibPDF/Value.h
@@ -0,0 +1,134 @@
+/*
+ * Copyright (c) 2021, Matthew Olsson <mattco@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Format.h>
+
+namespace PDF {
+
+class Object;
+
+class Value {
+public:
+    Value()
+        : m_type(Type::Null)
+    {
+    }
+
+    Value(bool b)
+        : m_type(Type::Bool)
+    {
+        m_as_bool = b;
+    }
+
+    Value(int i)
+        : m_type(Type::Int)
+    {
+        m_as_int = i;
+    }
+
+    Value(float f)
+        : m_type(Type::Float)
+    {
+        m_as_float = f;
+    }
+
+    template<IsObject T>
+    Value(NonnullRefPtr<T> obj)
+        : m_type(Type::Object)
+    {
+        obj->ref();
+        m_as_object = obj;
+    }
+
+    Value(const Value& other)
+    {
+        *this = other;
+    }
+
+    ~Value();
+
+    Value& operator=(const Value& other);
+
+    [[nodiscard]] ALWAYS_INLINE bool is_null() const { return m_type == Type::Null; }
+    [[nodiscard]] ALWAYS_INLINE bool is_bool() const { return m_type == Type::Bool; }
+    [[nodiscard]] ALWAYS_INLINE bool is_int() const { return m_type == Type::Int; }
+    [[nodiscard]] ALWAYS_INLINE bool is_float() const { return m_type == Type::Float; }
+    [[nodiscard]] ALWAYS_INLINE bool is_number() const { return is_int() || is_float(); }
+
+    [[nodiscard]] ALWAYS_INLINE bool is_object() const { return m_type == Type::Object; }
+
+    [[nodiscard]] ALWAYS_INLINE bool as_bool() const
+    {
+        VERIFY(is_bool());
+        return m_as_bool;
+    }
+
+    [[nodiscard]] ALWAYS_INLINE int as_int() const
+    {
+        VERIFY(is_int());
+        return m_as_int;
+    }
+
+    [[nodiscard]] ALWAYS_INLINE int to_int() const
+    {
+        if (is_int())
+            return as_int();
+        return static_cast<int>(as_float());
+    }
+
+    [[nodiscard]] ALWAYS_INLINE float as_float() const
+    {
+        VERIFY(is_float());
+        return m_as_float;
+    }
+
+    [[nodiscard]] ALWAYS_INLINE float to_float() const
+    {
+        if (is_float())
+            return as_float();
+        return static_cast<float>(as_int());
+    }
+
+    [[nodiscard]] ALWAYS_INLINE NonnullRefPtr<Object> as_object() const { return *m_as_object; }
+
+    [[nodiscard]] ALWAYS_INLINE explicit operator bool() const { return !is_null(); }
+
+    [[nodiscard]] String to_string(int indent = 0) const;
+
+private:
+    enum class Type {
+        Null,
+        Bool,
+        Int,
+        Float,
+        Object,
+    };
+
+    union {
+        bool m_as_bool;
+        int m_as_int;
+        float m_as_float;
+        Object* m_as_object;
+    };
+
+    Type m_type;
+};
+
+}
+
+namespace AK {
+
+template<>
+struct Formatter<PDF::Value> : Formatter<StringView> {
+    void format(FormatBuilder& builder, const PDF::Value& value)
+    {
+        Formatter<StringView>::format(builder, value.to_string());
+    }
+};
+
+}