diff --git a/README.md b/README.md
index f68b7f7..764480f 100644
--- a/README.md
+++ b/README.md
@@ -3,7 +3,7 @@ Automatic copy-on-write semantic memory slices for use in C (and C++)
 
 # Usage
 See `include/cow.h` for documentation on each function.
-Each function, macro, and type definition in the header will be prefixed with `cow_` or `COW_`.
+Each function, macro, and type definition in the header will be prefixed with `cow_` or `COW_`. Internal non-prototpyed items use the namespace `_cow_` or `_COW_`.
 
 ## Building
 Run `make` to build to build the `release` (optimised) target of the library.
diff --git a/include/cow.h b/include/cow.h
index af9fc4f..6249fdb 100644
--- a/include/cow.h
+++ b/include/cow.h
@@ -9,7 +9,7 @@ extern "C" {
 #include <stdlib.h>
 
 // Copy-on-write mapped memory.
-typedef struct cow cow_t;
+typedef struct cow_mapped_slice cow_t;
 
 /// Create a new copy-on-write area of `size` bytes. 
 /// Writes to this instance pointer (`cow_ptr()`) are written to the allocated memory.
diff --git a/src/cow.c b/src/cow.c
index de79f11..cd5e95a 100644
--- a/src/cow.c
+++ b/src/cow.c
@@ -31,14 +31,8 @@
 #define LASSERT(expr, msg) ASSERT(LIKELY(expr), "(unexpected) " msg)
 #define UASSERT(expr, msg) ASSERT(UNLIKELY(expr), "(expected) " msg)
 
-struct cow {
-	void* origin; // ptr to mapped memory. This *MUST* be the first field and have an offset of 0.
-
-	int fd; // Will be ORd with ~INT_MAX if it's a clone. Will be >0 if it's the original.
-	size_t size;
-}; // cow_t, *cow
-
-_Static_assert(offsetof(cow_t, origin) == 0, "`cow_t.origin` must have an offset of 0.");
+// struct cow { ... }
+#include "cow_t.h"
 
 static __attribute__((noreturn)) __attribute__((noinline)) __attribute__((cold)) void die(const char* error)
 {
@@ -92,7 +86,7 @@ size_t cow_size(const cow_t* cow)
 	return cow->size;
 }
 
-cow_t* cow_create(size_t size)
+inline internal cow_t _cow_create_unboxed(size_t size)
 {
 	cow_t ret;
 	ret.size = size;
@@ -101,15 +95,24 @@ cow_t* cow_create(size_t size)
 	if(ret.origin == MAP_FAILED) die("cow_create:mmap");
 
 	TRACE("mapped new origin cow page of %lu size at %p (memfd %d)", size, ret.origin, ret.fd);
-	return box_value(ret);
+	return ret;
+}
+cow_t* cow_create(size_t size)
+{	
+	return box_value(_cow_create_unboxed(size));
 }
 
-void cow_free(cow_t* restrict cow)
+inline internal void _cow_free_unboxed(const cow_t* cow)
 {
 	TRACE("unmapping %s cow of %lu size from %p (fd %d, real fd %d)", cow_is_fake(cow) ? "fake" : "and closing fd of origin", cow->size, cow->origin, cow->fd, cow_real_fd(cow));
 	munmap(cow->origin, cow->size);
 	if(!cow_is_fake(cow))
 		close(cow->fd);
+}
+
+void cow_free(cow_t* restrict cow)
+{
+	_cow_free_unboxed(cow);
 	free(cow);
 }
 
diff --git a/src/cow.cpp b/src/cow.cpp
index af7ceb3..f7faf80 100644
--- a/src/cow.cpp
+++ b/src/cow.cpp
@@ -2,8 +2,13 @@
 
 #include <utility>
 
+#include "cow_t.h"
+
 struct Cow::_inner {
-	cow_t* ptr;
+	cow_t cow;
+
+	inline const cow_t* ptr() const { return &cow; }
+	inline cow_t* ptr() { return &cow; }
 
 	~_inner();
 	_inner(size_t sz);
@@ -14,13 +19,13 @@ struct Cow::_inner {
 	_inner() = delete;
 };
 Cow::_inner::~_inner() {
-	if(ptr) {
-		cow_free(ptr);
-		ptr = nullptr;
-	}
+	_cow_free_unboxed(ptr());
+}
+Cow::_inner::_inner(size_t sz) : cow(_cow_create_unboxed(sz)){}
+Cow::_inner::_inner(cow_t* ptr) : cow(*ptr)
+{
+	free(ptr);
 }
-Cow::_inner::_inner(size_t sz) : ptr(cow_create(sz)){}
-Cow::_inner::_inner(cow_t* ptr) : ptr(ptr){}
 
 Cow::Cow(size_t size) : super(std::make_shared<_inner>(size)){}
 Cow::Cow(cow_t* raw) : super(std::make_shared<_inner>(raw)){}
@@ -32,9 +37,9 @@ Cow::~Cow(){}
 Cow Cow::from_raw(cow_t* owned) { if(cow_is_fake(owned)) throw "Trying to create real from fake raw"; else return Cow(owned); }
 
 Cow::Fake Cow::clone() const { return Fake::from_real(*this); }
-cow_t* Cow::get_raw() const { return super->ptr; }
+cow_t* Cow::get_raw() const { return super->ptr(); }
 
-Cow::Fake::Fake(const Cow& copy) : Cow(copy), fake(cow_clone(copy.super->ptr)){}
+Cow::Fake::Fake(const Cow& copy) : Cow(copy), fake(cow_clone(copy.super->ptr())){}
 Cow::Fake::Fake(const Fake& copy) : Cow(copy), fake(cow_clone(copy.fake)){}//Fake(*static_cast<const Cow*>(&copy)){}
 Cow::Fake::Fake(Fake&& move) : Cow(std::move(move)), fake(move.fake)
 {
diff --git a/src/cow_t.h b/src/cow_t.h
new file mode 100644
index 0000000..2267c62
--- /dev/null
+++ b/src/cow_t.h
@@ -0,0 +1,38 @@
+// Internal header for defining the `cow_t` concrete type to be used with the C and C++ APIs.
+#ifndef _COW_T_H
+#define _COW_T_H
+
+#define internal __attribute__((visibility("internal")))
+
+#ifdef __cplusplus
+#define restrict __restrict__
+extern "C" {
+#endif
+
+#include <stdlib.h>
+
+#include <cow.h>
+
+struct cow_mapped_slice {
+	void* origin; // ptr to mapped memory. This *MUST* be the first field and have an offset of 0.
+
+	int fd; // Will be ORd with ~INT_MAX if it's a clone. Will be >0 if it's the original.
+	size_t size;
+}; // cow_t, *cow
+
+#ifdef __cplusplus
+static_assert
+#else
+_Static_assert
+#endif
+		(offsetof(cow_t, origin) == 0, "`cow_t.origin` must have an offset of 0.");
+
+cow_t _cow_create_unboxed(size_t size) internal;
+void _cow_free_unboxed(const cow_t* cow) internal;
+
+#ifdef __cplusplus
+}
+#undef restruct
+#endif
+
+#endif /* _COW_T_H */