[kutil] Rename 'size' to 'order' when meaning 2^N

Heap allocator is a buddy allocator that deals with power-of-two block
sizes. Previously it referred to both a number of bytes and an order of
magnitude as a 'size'. Rename functions and variables referring to
orders of magnitude to 'order'.

Tags: pedantry

src/libraries/kutil/heap_allocator.cpp

@@ -7,15 +7,15 @@ namespace kutil {
 
 struct heap_allocator::mem_header
 {
-	mem_header(mem_header *prev, mem_header *next, uint8_t size) :
+	mem_header(mem_header *prev, mem_header *next, uint8_t order) :
 		m_prev(prev), m_next(next)
 	{
-		set_size(size);
+		set_order(order);
 	}
 
-	inline void set_size(uint8_t size) {
+	inline void set_order(uint8_t order) {
 		m_prev = reinterpret_cast<mem_header *>(
-			reinterpret_cast<uintptr_t>(prev()) | (size & 0x3f));
+			reinterpret_cast<uintptr_t>(prev()) | (order & 0x3f));
 	}
 
 	inline void set_used(bool used) {
@@ -30,9 +30,9 @@ struct heap_allocator::mem_header
 	}
 
 	inline void set_prev(mem_header *prev) {
-		uint8_t s = size();
+		uint8_t s = order();
 		m_prev = prev;
-		set_size(s);
+		set_order(s);
 	}
 
 	void remove() {
@@ -47,12 +47,12 @@ struct heap_allocator::mem_header
 
 	inline mem_header * buddy() const {
 		return reinterpret_cast<mem_header *>(
-			reinterpret_cast<uintptr_t>(this) ^ (1 << size()));
+			reinterpret_cast<uintptr_t>(this) ^ (1 << order()));
 	}
 
 	inline bool eldest() const { return this < buddy(); }
 
-	inline uint8_t size() const { return reinterpret_cast<uintptr_t>(m_prev) & 0x3f; }
+	inline uint8_t order() const { return reinterpret_cast<uintptr_t>(m_prev) & 0x3f; }
 	inline bool used() const { return reinterpret_cast<uintptr_t>(m_next) & 0x1; }
 
 private:
@@ -73,16 +73,17 @@ void *
 heap_allocator::allocate(size_t length)
 {
 	size_t total = length + sizeof(mem_header);
-	unsigned size = min_size;
-	while (total > (1 << size)) size++;
 
-	kassert(size <= max_size, "Tried to allocate a block bigger than max_size");
-	if (size > max_size)
+	unsigned order = min_order;
+	while (total > (1 << order)) order++;
+
+	kassert(order <= max_order, "Tried to allocate a block bigger than max_order");
+	if (order > max_order)
 		return nullptr;
 
-	mem_header *header = pop_free(size);
+	mem_header *header = pop_free(order);
 	header->set_used(true);
-	m_allocated_size += (1 << size);
+	m_allocated_size += (1 << order);
 	return header + 1;
 }
 
@@ -94,66 +95,66 @@ heap_allocator::free(void *p)
 	mem_header *header = reinterpret_cast<mem_header *>(p);
 	header -= 1; // p points after the header
 	header->set_used(false);
-	m_allocated_size -= (1 << header->size());
+	m_allocated_size -= (1 << header->order());
 
-	while (header->size() != max_size) {
-		auto size = header->size();
+	while (header->order() != max_order) {
+		auto order = header->order();
 
 		mem_header *buddy = header->buddy();
-		if (buddy->used() || buddy->size() != size)
+		if (buddy->used() || buddy->order() != order)
 			break;
 
-		if (get_free(size) == buddy)
-			get_free(size) = buddy->next();
+		if (get_free(order) == buddy)
+			get_free(order) = buddy->next();
 
 		buddy->remove();
 
 		header = header->eldest() ? header : buddy;
-		header->set_size(size + 1);
+		header->set_order(order + 1);
 	}
 
-	uint8_t size = header->size();
-	header->set_next(get_free(size));
-	get_free(size) = header;
+	uint8_t order = header->order();
+	header->set_next(get_free(order));
+	get_free(order) = header;
 	if (header->next())
 		header->next()->set_prev(header);
 }
 
 void
-heap_allocator::ensure_block(unsigned size)
+heap_allocator::ensure_block(unsigned order)
 {
-	if (get_free(size) != nullptr)
+	if (get_free(order) != nullptr)
 		return;
 
-	if (size == max_size) {
-		size_t bytes = (1 << max_size);
+	if (order == max_order) {
+		size_t bytes = (1 << max_order);
 		if (bytes <= m_size) {
 			mem_header *next = reinterpret_cast<mem_header *>(m_next);
-			new (next) mem_header(nullptr, nullptr, size);
-			get_free(size) = next;
+			new (next) mem_header(nullptr, nullptr, order);
+			get_free(order) = next;
 			m_next += bytes;
 			m_size -= bytes;
 		}
 	} else {
-		mem_header *orig = pop_free(size + 1);
+		mem_header *orig = pop_free(order + 1);
 		if (orig) {
-			mem_header *next = kutil::offset_pointer(orig, 1 << size);
-			new (next) mem_header(orig, nullptr, size);
+			mem_header *next = kutil::offset_pointer(orig, 1 << order);
+			new (next) mem_header(orig, nullptr, order);
 
 			orig->set_next(next);
-			orig->set_size(size);
-			get_free(size) = orig;
+			orig->set_order(order);
+			get_free(order) = orig;
 		}
 	}
 }
 
 heap_allocator::mem_header *
-heap_allocator::pop_free(unsigned size)
+heap_allocator::pop_free(unsigned order)
 {
-	ensure_block(size);
-	mem_header *block = get_free(size);
+	ensure_block(order);
+	mem_header *block = get_free(order);
 	if (block) {
-		get_free(size) = block->next();
+		get_free(order) = block->next();
 		block->remove();
 	}
 	return block;

src/libraries/kutil/include/kutil/heap_allocator.h

@@ -29,32 +29,32 @@ public:
 	/// \arg p  A pointer previously retuned by allocate()
 	virtual void free(void *p);
 
-	/// Minimum block size is (2^min_size). Must be at least 6.
-	static const unsigned min_size = 6;
+	/// Minimum block size is (2^min_order). Must be at least 6.
+	static const unsigned min_order = 6;
 
-	/// Maximum block size is (2^max_size). Must be less than 64.
-	static const unsigned max_size = 22;
+	/// Maximum block size is (2^max_order). Must be less than 64.
+	static const unsigned max_order = 22;
 
 protected:
 	class mem_header;
 
-	/// Ensure there is a block of a given size, recursively splitting
-	/// \arg size   Size category of the block we want
-	void ensure_block(unsigned size);
+	/// Ensure there is a block of a given order, recursively splitting
+	/// \arg order   Order (2^N) of the block we want
+	void ensure_block(unsigned order);
 
-	/// Helper accessor for the list of blocks of a given size
-	/// \arg size   Size category of the block we want
+	/// Helper accessor for the list of blocks of a given order
+	/// \arg order  Order (2^N) of the block we want
 	/// \returns    A mutable reference to the head of the list
-	mem_header *& get_free(unsigned size)  { return m_free[size - min_size]; }
+	mem_header *& get_free(unsigned order)  { return m_free[order - min_order]; }
 
-	/// Helper to get a block of the given size, growing if necessary
-	/// \arg size   Size category of the block we want
-	/// \returns    A detached block of the given size
-	mem_header * pop_free(unsigned size);
+	/// Helper to get a block of the given order, growing if necessary
+	/// \arg order  Order (2^N) of the block we want
+	/// \returns    A detached block of the given order
+	mem_header * pop_free(unsigned order);
 
 	uintptr_t m_next;
 	size_t m_size;
-	mem_header *m_free[max_size - min_size + 1];
+	mem_header *m_free[max_order - min_order + 1];
 	size_t m_allocated_size;
 
 	heap_allocator(const heap_allocator &) = delete;