From b16d7c6a8772e5b043a629211eff79d0be9d2558 Mon Sep 17 00:00:00 2001
From: Avril <flanchan@cumallover.me>
Date: Sat, 5 Jun 2021 11:39:00 +0100
Subject: [PATCH] added slice

---
 include/cow.hpp   | 23 ++++++-----------------
 include/slice.hpp | 33 +++++++++++++++++++++++++++++++++
 src/test/main.cpp | 28 ++++++++++++++++++++++------
 3 files changed, 61 insertions(+), 23 deletions(-)
 create mode 100644 include/slice.hpp

diff --git a/include/cow.hpp b/include/cow.hpp
index 70c6e15..ab1364e 100644
--- a/include/cow.hpp
+++ b/include/cow.hpp
@@ -4,8 +4,9 @@
 
 #include <memory>
 
+#include "slice.hpp"
 
-struct Cow {
+struct Cow : public Slice<unsigned char> {
 	struct Fake;
 	Cow() = delete;
 
@@ -15,13 +16,13 @@ struct Cow {
 
 	virtual Fake clone() const;
 
-	inline void* area() { return cow_ptr(get_raw()); }
-	inline const void* area() const { return cow_ptr_of(const void, get_raw()); }
+	inline void* area() override { return cow_ptr(get_raw()); }
+	inline const void* area() const override { return cow_ptr_of(const void, get_raw()); }
 
 	/// Get the size of the mapped area.
 	///
 	/// Note: This calls into `_inner`'s internals. To skip the call on non-LTO builds, use `size_unsafe()`.
-	size_t size() const;
+	size_t size() const override;
 	/// Get the size by assuming the ABI layout of cow_t to be correct. Potentially faster but ABI sensitive.
 	/// This shouldn't be a problem if all build static assertions passed.
 	///
@@ -31,18 +32,6 @@ struct Cow {
 	/// XXX: Deprecated function for now. It seems `size()` offers better codegen on LTO and non-LTO enabled builds.
 	[[deprecated]] inline size_t size_unsafe() const { return _cow_size_unsafe(get_raw()); }
 	
-	inline unsigned char* as_bytes() { return (unsigned char*)area(); }
-	inline const unsigned char* as_bytes() const { return (const unsigned char*)area(); }
-
-	inline unsigned char& operator[](size_t index) {
-		if(index >= size()) throw "Size too large";
-		return as_bytes()[index];
-	}
-	inline const unsigned char& operator[](size_t index) const {
-		if(index >= size()) throw "Size too large";
-		return as_bytes()[index];
-	}
-
 	static Cow from_raw(cow_t* owned);
 
 	private:
@@ -56,7 +45,7 @@ struct Cow {
 
 };
 
-struct Cow::Fake : Cow {
+struct Cow::Fake : public Cow {
 	Fake() = delete;
 	Fake(const Cow& real);
 	Fake(const Fake& copy);
diff --git a/include/slice.hpp b/include/slice.hpp
new file mode 100644
index 0000000..29f343e
--- /dev/null
+++ b/include/slice.hpp
@@ -0,0 +1,33 @@
+#pragma once
+
+template<typename T>
+struct Slice {
+	virtual const void* area() const =0;
+	virtual void* area() = 0;
+	virtual size_t size() const = 0;
+
+	inline T* ptr() { return (T*)area(); }
+	inline const T* ptr() const { return (const T*)area(); }
+
+	inline size_t size_bytes() const { return size() * sizeof(T); }
+
+	inline unsigned char* as_bytes() { return (unsigned char*)area(); }
+	inline const unsigned char* as_bytes() const { return (const unsigned char*)area(); }
+
+	inline T& operator[](size_t index) {
+		if(index >= size()) throw "Size too large";
+		return ptr()[index];
+	}
+	inline const T& operator[](size_t index) const {
+		if(index >= size()) throw "Size too large";
+		return ptr()[index];
+	}
+
+	template<typename U>
+	inline U* area_as() requires(sizeof(T) % sizeof(U) == 0) { return (U*)area(); }
+	template<typename U>
+	inline const U* area_as() const requires(sizeof(T) % sizeof(U) == 0) { return (U*)area(); }
+
+	template<typename U>
+	size_t size_as() const requires(sizeof(T) % sizeof(U) == 0) { return size_bytes() / sizeof(U); }
+};
diff --git a/src/test/main.cpp b/src/test/main.cpp
index 6878d99..f40771e 100644
--- a/src/test/main.cpp
+++ b/src/test/main.cpp
@@ -1,18 +1,34 @@
 #include <cow.hpp>
 
 #include <cstdio>
+#include <cstring>
+
+void write_fake(Cow& clone, const char* string)
+{
+	strncpy(clone.area_as<char>(), string, clone.size_as<char>()-1);
+}
+
+void read_fake(const Cow& clone)
+{
+	printf("read_fake: %s\n", clone.area_as<char>());
+}
 
 int main()
 {
 	Cow real(4096);
 
+	write_fake(real, "Hello world");
+	read_fake(real);
+	
+	Cow::Fake clone = real;
+	printf("Fake size: %lu\n", clone.size());
+	printf("Fake ptr: %p\n", clone.area());
 
-	printf("Fast size: %lu, slow size: %lu\n", real.size_unsafe(), real.size());
+	read_fake(clone);
+	write_fake(clone, "hello fake!");
+	read_fake(clone);
+	read_fake(real);
 
-	Cow::Fake clone = real;
-	{
-		Cow::Fake clone2 = clone;
-	}
-	if(0) cow_size_unsafe(NULL);
+	printf("First byte of: real = %x, fake = %x\n", real[0], clone[0]);
 	return 0;
 }