#include <assert.h>
#include <limits.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "tlsf.h"
#include "tlsfbits.h"

// Public constants: may be modified.
enum tlsf_public {
	// log2 of number of linear subdivisions of block sizes.
	SL_INDEX_COUNT_LOG2 = 5,
};

// Private constants: do not modify.
enum tlsf_private {
	// All allocation sizes and addresses are aligned to 4 bytes.
	ALIGN_SIZE_LOG2 = 2,
	ALIGN_SIZE = (1 << ALIGN_SIZE_LOG2),

	//
	// This code supports allocations of sizes up to (1 << FL_INDEX_MAX) bits.
	// However, because we linearly subdivide the second-level lists, and
	// our minimum size granularity is 4 bytes, it doesn't make sense to
	// create first-level lists for sizes smaller than SL_INDEX_COUNT * 4,
	// or (1 << (SL_INDEX_COUNT_LOG2 + 2)) bytes, as there we will be
	// trying to split size ranges into more slots than we have available.
	// Instead, we calculate the minimum threshold size, and place all
	// blocks below that size into the 0th first-level list.
	//

	FL_INDEX_MAX   		= 30,
	SL_INDEX_COUNT 		= (1 << SL_INDEX_COUNT_LOG2),
	FL_INDEX_SHIFT 		= (SL_INDEX_COUNT_LOG2 + ALIGN_SIZE_LOG2),
	FL_INDEX_COUNT 		= (FL_INDEX_MAX - FL_INDEX_SHIFT + 1),
	SMALL_BLOCK_SIZE	= (1 << FL_INDEX_SHIFT),
};

//
// Cast and min/max macros.
//

#define tlsf_cast(t, exp)	((t) (exp))
#define tlsf_min(a, b)		((a) < (b) ? (a) : (b))
#define tlsf_max(a, b)		((a) > (b) ? (a) : (b))

//
// Set assert macro, if it has not been provided by the user.
//

#if !defined (tlsf_assert)
#define tlsf_assert // Add an assert function here
#endif


//
// Static assertion mechanism.
//

#define _tlsf_glue2(x, y) x ## y
#define _tlsf_glue(x, y) _tlsf_glue2(x, y)
#define tlsf_static_assert(exp) \
	typedef char _tlsf_glue(static_assert, __LINE__) [(exp) ? 1 : -1]

// This code has been tested on 32- and 64-bit (LP/LLP) architectures.
tlsf_static_assert(sizeof(int) * CHAR_BIT == 32);
tlsf_static_assert(sizeof(size_t) * CHAR_BIT >= 32);
tlsf_static_assert(sizeof(size_t) * CHAR_BIT <= 64);

// SL_INDEX_COUNT must be <= number of bits in sl_bitmap's storage type.
tlsf_static_assert(sizeof(unsigned int) * CHAR_BIT >= SL_INDEX_COUNT);

// Ensure we've properly tuned our sizes.
tlsf_static_assert(ALIGN_SIZE == SMALL_BLOCK_SIZE / SL_INDEX_COUNT);

//
// Data structures and associated constants.
//

//
// Block header structure.
//
// There are several implementation subtleties involved:
// - The prev_phys_block field is only valid if the previous block is free.
// - The prev_phys_block field is actually stored at the end of the
//   previous block. It appears at the beginning of this structure only to
//   simplify the implementation.
// - The next_free / prev_free fields are only valid if the block is free.
//
typedef struct block_header_t
{
	// Points to the previous physical block.
	struct block_header_t* prev_phys_block;

	// The size of this block, excluding the block header.
	size_t size;

	// Next and previous free blocks.
	struct block_header_t* next_free;
	struct block_header_t* prev_free;
} block_header_t;

//
// Since block sizes are always at least a multiple of 4, the two least
// significant bits of the size field are used to store the block status:
// - bit 0: whether block is busy or free
// - bit 1: whether previous block is busy or free
//

static const size_t block_header_free_bit = 1 << 0;
static const size_t block_header_prev_free_bit = 1 << 1;

//
// The size of the block header exposed to used blocks is the size field.
// The prev_phys_block field is stored *inside* the previous free block.
//
static const size_t block_header_overhead = sizeof(size_t);

// User data starts directly after the size field in a used block.
static const size_t block_start_offset =
	offsetof(block_header_t, size) + sizeof(size_t);

//
// A free block must be large enough to store its header minus the size of
// the prev_phys_block field, and no larger than the number of addressable
// bits for FL_INDEX.
//
static const size_t block_size_min =
	sizeof(block_header_t) - sizeof(block_header_t*);
static const size_t block_size_max = tlsf_cast(size_t, 1) << FL_INDEX_MAX;


// The TLSF pool structure.
typedef struct pool_t
{
	// Empty lists point at this block to indicate they are free.
	block_header_t block_null;

	// Bitmaps for free lists.
	unsigned int fl_bitmap;
	unsigned int sl_bitmap[FL_INDEX_COUNT];

	// Head of free lists.
	block_header_t* blocks[FL_INDEX_COUNT][SL_INDEX_COUNT];
} pool_t;

// A type used for casting when doing pointer arithmetic.
typedef ptrdiff_t tlsfptr_t;

static void* tlsf_memcpy(void* dest, const void* src, size_t count)
{
	char* dst8 = (char*)dest;
	char* src8 = (char*)src;

	while (count--) {
		*dst8++ = *src8++;
	}
	return dest;
}

//
// block_header_t member functions.
//

static size_t block_size(const block_header_t* block)
{
	return block->size & ~(block_header_free_bit | block_header_prev_free_bit);
}

static void block_set_size(block_header_t* block, size_t size)
{
	const size_t oldsize = block->size;
	block->size = size | (oldsize & (block_header_free_bit | block_header_prev_free_bit));
}

static int block_is_last(const block_header_t* block)
{
	return 0 == block_size(block);
}

static int block_is_free(const block_header_t* block)
{
	return tlsf_cast(int, block->size & block_header_free_bit);
}

static void block_set_free(block_header_t* block)
{
	block->size |= block_header_free_bit;
}

static void block_set_used(block_header_t* block)
{
	block->size &= ~block_header_free_bit;
}

static int block_is_prev_free(const block_header_t* block)
{
	return tlsf_cast(int, block->size & block_header_prev_free_bit);
}

static void block_set_prev_free(block_header_t* block)
{
	block->size |= block_header_prev_free_bit;
}

static void block_set_prev_used(block_header_t* block)
{
	block->size &= ~block_header_prev_free_bit;
}

static block_header_t* block_from_ptr(const void* ptr)
{
	return tlsf_cast(block_header_t*,
		tlsf_cast(unsigned char*, ptr) - block_start_offset);
}

static void* block_to_ptr(const block_header_t* block)
{
	return tlsf_cast(void*,
		tlsf_cast(unsigned char*, block) + block_start_offset);
}

// Return location of next block after block of given size.
static block_header_t* offset_to_block(const void* ptr, size_t size)
{
	return tlsf_cast(block_header_t*, tlsf_cast(tlsfptr_t, ptr) + size);
}

// Return location of previous block.
static block_header_t* block_prev(const block_header_t* block)
{
	return block->prev_phys_block;
}

// Return location of next existing block.
static block_header_t* block_next(const block_header_t* block)
{
	block_header_t* next = offset_to_block(block_to_ptr(block),
		block_size(block) - block_header_overhead);
	tlsf_assert(!block_is_last(block));
	return next;
}

// Link a new block with its physical neighbor, return the neighbor.
static block_header_t* block_link_next(block_header_t* block)
{
	block_header_t* next = block_next(block);
	next->prev_phys_block = block;
	return next;
}

static void block_mark_as_free(block_header_t* block)
{
	// Link the block to the next block, first.
	block_header_t* next = block_link_next(block);
	block_set_prev_free(next);
	block_set_free(block);
}

static void block_mark_as_used(block_header_t* block)
{
	block_header_t* next = block_next(block);
	block_set_prev_used(next);
	block_set_used(block);
}

static size_t align_up(size_t x, size_t align)
{
	tlsf_assert(0 == (align & (align - 1)) && "must align to a power of two");
	return (x + (align - 1)) & ~(align - 1);
}

static size_t align_down(size_t x, size_t align)
{
	tlsf_assert(0 == (align & (align - 1)) && "must align to a power of two");
	return x - (x & (align - 1));
}

static void* align_ptr(const void* ptr, size_t align)
{
	const tlsfptr_t aligned =
		(tlsf_cast(tlsfptr_t, ptr) + (align - 1)) & ~(align - 1);
	tlsf_assert(0 == (align & (align - 1)) && "must align to a power of two");
	return tlsf_cast(void*, aligned);
}

//
// Adjust an allocation size to be aligned to word size, and no smaller
// than internal minimum.
//
static size_t adjust_request_size(size_t size, size_t align)
{
	size_t adjust = 0;
	if (size && size < block_size_max) {
		const size_t aligned = align_up(size, align);
		adjust = tlsf_max(aligned, block_size_min);
	}
	return adjust;
}

//
// TLSF utility functions. In most cases, these are direct translations of
// the documentation found in the white paper.
//

static void mapping_insert(size_t size, int* fli, int* sli)
{
	int fl, sl;
	if (size < SMALL_BLOCK_SIZE) {
		// Store small blocks in first list.
		fl = 0;
		sl = tlsf_cast(int, size) / (SMALL_BLOCK_SIZE / SL_INDEX_COUNT);
	} else {
		fl = tlsf_fls_sizet(size);
		sl = tlsf_cast(int, size >> (fl - SL_INDEX_COUNT_LOG2)) ^ (1 << SL_INDEX_COUNT_LOG2);
		fl -= (FL_INDEX_SHIFT - 1);
	}
	*fli = fl;
	*sli = sl;
}

// This version rounds up to the next block size (for allocations)
static void mapping_search(size_t size, int* fli, int* sli)
{
	if (size >= (1 << SL_INDEX_COUNT_LOG2)) {
		const size_t round = (1 << (tlsf_fls_sizet(size) - SL_INDEX_COUNT_LOG2)) - 1;
		size += round;
	}
	mapping_insert(size, fli, sli);
}

static block_header_t* search_suitable_block(pool_t* pool, int* fli, int* sli)
{
	int fl = *fli;
	int sl = *sli;

	//
	// First, search for a block in the list associated with the given
	// fl/sl index.
	//
	unsigned int sl_map = pool->sl_bitmap[fl] & (~0 << sl);
	if (!sl_map) {
		// No block exists. Search in the next largest first-level list.
		const unsigned int fl_map = pool->fl_bitmap & (~0 << (fl + 1));
		if (!fl_map) {
			// No free blocks available, memory has been exhausted.
			return 0;
		}
		fl = tlsf_ffs(fl_map);
		*fli = fl;
		sl_map = pool->sl_bitmap[fl];
	}
	tlsf_assert(sl_map && "internal error - second level bitmap is null");
	sl = tlsf_ffs(sl_map);
	*sli = sl;
	// Return the first block in the free list.
	return pool->blocks[fl][sl];
}

// Remove a free block from the free list.
static void remove_free_block(pool_t* pool, block_header_t* block, int fl, int sl)
{
	block_header_t* prev = block->prev_free;
	block_header_t* next = block->next_free;
	tlsf_assert(prev && "prev_free field can not be null");
	tlsf_assert(next && "next_free field can not be null");
	next->prev_free = prev;
	prev->next_free = next;

	// If this block is the head of the free list, set new head.
	if (pool->blocks[fl][sl] == block) {
		pool->blocks[fl][sl] = next;
		// If the new head is null, clear the bitmap.
		if (next == &pool->block_null) {
			pool->sl_bitmap[fl] &= ~(1 << sl);
			/* If the second bitmap is now empty, clear the fl bitmap. */
			if (!pool->sl_bitmap[fl]) {
				pool->fl_bitmap &= ~(1 << fl);
			}
		}
	}
}

// Insert a free block into the free block list.
static void insert_free_block(pool_t* pool, block_header_t* block, int fl, int sl)
{
	block_header_t* current = pool->blocks[fl][sl];
	tlsf_assert(current && "free list cannot have a null entry");
	tlsf_assert(block && "cannot insert a null entry into the free list");
	block->next_free = current;
	block->prev_free = &pool->block_null;
	current->prev_free = block;

	tlsf_assert(block_to_ptr(block) == align_ptr(block_to_ptr(block), ALIGN_SIZE)
		&& "block not aligned properly");
	//
	// Insert the new block at the head of the list, and mark the first-
	// and second-level bitmaps appropriately.
	//
	pool->blocks[fl][sl] = block;
	pool->fl_bitmap |= (1 << fl);
	pool->sl_bitmap[fl] |= (1 << sl);
}

// Remove a given block from the free list.
static void block_remove(pool_t* pool, block_header_t* block)
{
	int fl, sl;
	mapping_insert(block_size(block), &fl, &sl);
	remove_free_block(pool, block, fl, sl);
}

// Insert a given block into the free list.
static void block_insert(pool_t* pool, block_header_t* block)
{
	int fl, sl;
	mapping_insert(block_size(block), &fl, &sl);
	insert_free_block(pool, block, fl, sl);
}

static int block_can_split(block_header_t* block, size_t size)
{
	return block_size(block) >= sizeof(block_header_t) + size;
}

// Split a block into two, the second of which is free.
static block_header_t* block_split(block_header_t* block, size_t size)
{
	/* Calculate the amount of space left in the remaining block. */
	block_header_t* remaining =
		offset_to_block(block_to_ptr(block), size - block_header_overhead);

	const size_t remain_size = block_size(block) - (size + block_header_overhead);

	tlsf_assert(block_to_ptr(remaining) == align_ptr(block_to_ptr(remaining), ALIGN_SIZE)
		&& "remaining block not aligned properly");

	tlsf_assert(block_size(block) == remain_size + size + block_header_overhead);
	block_set_size(remaining, remain_size);
	tlsf_assert(block_size(remaining) >= block_size_min && "block split with invalid size");

	block_set_size(block, size);
	block_mark_as_free(remaining);

	return remaining;
}

// Absorb a free block's storage into an adjacent previous free block.
static block_header_t* block_absorb(block_header_t* prev, block_header_t* block)
{
	tlsf_assert(!block_is_last(prev) && "previous block can't be last!");
	/* Note: Leaves flags untouched. */
	prev->size += block_size(block) + block_header_overhead;
	block_link_next(prev);
	return prev;
}

// Merge a just-freed block with an adjacent previous free block.
static block_header_t* block_merge_prev(pool_t* pool, block_header_t* block)
{
	if (block_is_prev_free(block)) {
		block_header_t* prev = block_prev(block);
		tlsf_assert(prev && "prev physical block can't be null");
		tlsf_assert(block_is_free(prev) && "prev block is not free though marked as such");
		block_remove(pool, prev);
		block = block_absorb(prev, block);
	}
	return block;
}

// Merge a just-freed block with an adjacent free block.
static block_header_t* block_merge_next(pool_t* pool, block_header_t* block)
{
	block_header_t* next = block_next(block);
	tlsf_assert(next && "next physical block can't be null");

	if (block_is_free(next)) {
		tlsf_assert(!block_is_last(block) && "previous block can't be last!");
		block_remove(pool, next);
		block = block_absorb(block, next);
	}

	return block;
}

// Trim any trailing block space off the end of a block, return to pool.
static void block_trim_free(pool_t* pool, block_header_t* block, size_t size)
{
	tlsf_assert(block_is_free(block) && "block must be free");
	if (block_can_split(block, size)) {
		block_header_t* remaining_block = block_split(block, size);
		block_link_next(block);
		block_set_prev_free(remaining_block);
		block_insert(pool, remaining_block);
	}
}

// Trim any trailing block space off the end of a used block, return to pool.
static void block_trim_used(pool_t* pool, block_header_t* block, size_t size)
{
	tlsf_assert(!block_is_free(block) && "block must be used");
	if (block_can_split(block, size)) {
		/* If the next block is free, we must coalesce. */
		block_header_t* remaining_block = block_split(block, size);
		block_set_prev_used(remaining_block);

		remaining_block = block_merge_next(pool, remaining_block);
		block_insert(pool, remaining_block);
	}
}

static block_header_t* block_trim_free_leading(pool_t* pool, block_header_t* block, size_t size)
{
	block_header_t* remaining_block = block;
	if (block_can_split(block, size)) {
		/* We want the 2nd block. */
		remaining_block = block_split(block, size - block_header_overhead);
		block_set_prev_free(remaining_block);

		block_link_next(block);
		block_insert(pool, block);
	}
	return remaining_block;
}

static block_header_t* block_locate_free(pool_t* pool, size_t size)
{
	int fl = 0, sl = 0;
	block_header_t* block = 0;

	if (size) {
		mapping_search(size, &fl, &sl);
		block = search_suitable_block(pool, &fl, &sl);
	}

	if (block) {
		tlsf_assert(block_size(block) >= size);
		remove_free_block(pool, block, fl, sl);
	}

	return block;
}

static void* block_prepare_used(pool_t* pool, block_header_t* block, size_t size)
{
	void* p = 0;
	if (block) {
		block_trim_free(pool, block, size);
		block_mark_as_used(block);
		p = block_to_ptr(block);
	}
	return p;
}

// Clear structure and point all empty lists at the null block.
static void pool_construct(pool_t* pool)
{
	int i, j;

	pool->block_null.next_free = &pool->block_null;
	pool->block_null.prev_free = &pool->block_null;

	pool->fl_bitmap = 0;
	for (i = 0; i < FL_INDEX_COUNT; ++i) {
		pool->sl_bitmap[i] = 0;
		for (j = 0; j < SL_INDEX_COUNT; ++j) {
			pool->blocks[i][j] = &pool->block_null;
		}
	}
}

//
// Debugging utilities.
///

typedef struct integrity_t
{
	int prev_status;
	int status;
} integrity_t;

#define tlsf_insist(x) { tlsf_assert(x); if (!(x)) { status--; } }

static void integrity_walker(void* ptr, size_t size, int used, void* user)
{
	(void)used;

	block_header_t* block = block_from_ptr(ptr);
	integrity_t* integ = tlsf_cast(integrity_t*, user);
	const int this_prev_status = block_is_prev_free(block) ? 1 : 0;
	const int this_status = block_is_free(block) ? 1 : 0;
	const size_t this_block_size = block_size(block);

	int status = 0;
	tlsf_insist(integ->prev_status == this_prev_status && "prev status incorrect");
	tlsf_insist(size == this_block_size && "block size incorrect");

	integ->prev_status = this_status;
	integ->status += status;
}

int tlsf_check_heap(tlsf_pool tlsf)
{
	int i, j;

	pool_t* pool = tlsf_cast(pool_t*, tlsf);
	int status = 0;

	/* Check that the blocks are physically correct. */
	integrity_t integ = { 0, 0 };
	tlsf_walk_heap(tlsf, integrity_walker, &integ);
	status = integ.status;

	/* Check that the free lists and bitmaps are accurate. */
	for (i = 0; i < FL_INDEX_COUNT; ++i) {
		for (j = 0; j < SL_INDEX_COUNT; ++j) {
			const int fl_map = pool->fl_bitmap & (1 << i);
			const int sl_list = pool->sl_bitmap[i];
			const int sl_map = sl_list & (1 << j);
			const block_header_t* block = pool->blocks[i][j];

			/* Check that first- and second-level lists agree. */
			if (!fl_map) {
				tlsf_insist(!sl_map && "second-level map must be null");
			}

			if (!sl_map) {
				tlsf_insist(block == &pool->block_null && "block list must be null");
				continue;
			}

			// Check that there is at least one free block.
			tlsf_insist(sl_list && "no free blocks in second-level map");
			tlsf_insist(block != &pool->block_null && "block should not be null");

			while (block != &pool->block_null) {
				int fli, sli;
				tlsf_insist(block_is_free(block) && "block should be free");
				tlsf_insist(!block_is_prev_free(block) && "blocks should have coalesced");
				tlsf_insist(!block_is_free(block_next(block)) && "blocks should have coalesced");
				tlsf_insist(block_is_prev_free(block_next(block)) && "block should be free");
				tlsf_insist(block_size(block) >= block_size_min && "block not minimum size");

				mapping_insert(block_size(block), &fli, &sli);
				tlsf_insist(fli == i && sli == j && "block size indexed in wrong list");
				block = block->next_free;
			}
		}
	}

	return status;
}

#undef tlsf_insist

static void default_walker(void* ptr, size_t size, int used, void* user)
{
#if 0
	(void)user;
	printf("\t%p %s size: %x (%p)\n", ptr, used ? "used" : "free", (unsigned int)size, block_from_ptr(ptr));
#endif
}

void tlsf_walk_heap(tlsf_pool pool, tlsf_walker walker, void* user)
{
	tlsf_walker heap_walker = walker ? walker : default_walker;
	block_header_t* block =
		offset_to_block(pool, sizeof(pool_t) - block_header_overhead);

	while (block && !block_is_last(block)) {
		heap_walker(
			block_to_ptr(block),
			block_size(block),
			!block_is_free(block),
			user);
		block = block_next(block);
	}
}

size_t tlsf_block_size(void* ptr)
{
	size_t size = 0;
	if (ptr) {
		const block_header_t* block = block_from_ptr(ptr);
		size = block_size(block);
	}
	return size;
}

//
// Overhead of the TLSF structures in a given memory block passed to
// tlsf_create, equal to the size of a pool_t plus overhead of the initial
// free block and the sentinel block.
//
size_t tlsf_overhead()
{
	const size_t pool_overhead = sizeof(pool_t) + 2 * block_header_overhead;
	return pool_overhead;
}

//
// TLSF main interface. Right out of the white paper.
//

tlsf_pool tlsf_create(void* mem, size_t bytes)
{
	block_header_t* block;
	block_header_t* next;

	const size_t pool_overhead = tlsf_overhead();
	const size_t pool_bytes = align_down(bytes - pool_overhead, ALIGN_SIZE);
	pool_t* pool = tlsf_cast(pool_t*, mem);


	if (pool_bytes < block_size_min || pool_bytes > block_size_max) {
#if 0
		printf("tlsf_create: Pool size must be between %u and %u bytes.\n",
			(unsigned int)(pool_overhead + block_size_min),
			(unsigned int)(pool_overhead + block_size_max));
#endif
		return 0;
	}

	// Construct a valid pool object.
	pool_construct(pool);

	//
	// Create the main free block. Offset the start of the block slightly
	// so that the prev_phys_block field falls inside of the pool
	// structure - it will never be used.
	//
	block = offset_to_block(
		tlsf_cast(void*, pool), sizeof(pool_t) - block_header_overhead);
	block_set_size(block, pool_bytes);
	block_set_free(block);
	block_set_prev_used(block);
	block_insert(pool, block);

	// Split the block to create a zero-size pool sentinel block.
	next = block_link_next(block);
	block_set_size(next, 0);
	block_set_used(next);
	block_set_prev_free(next);

	return tlsf_cast(tlsf_pool, pool);
}

void tlsf_destroy(tlsf_pool pool)
{
	// Nothing to do.
	(void) pool;
}

void* tlsf_malloc(tlsf_pool tlsf, size_t size)
{
	pool_t* pool = tlsf_cast(pool_t*, tlsf);
	const size_t adjust = adjust_request_size(size, ALIGN_SIZE);
	block_header_t* block = block_locate_free(pool, adjust);
	return block_prepare_used(pool, block, adjust);
}

void* tlsf_memalign(tlsf_pool tlsf, size_t align, size_t size)
{
	pool_t* pool = tlsf_cast(pool_t*, tlsf);
	const size_t adjust = adjust_request_size(size, ALIGN_SIZE);

	//
	// We must allocate an additional minimum block size bytes so that if
	// our free block will leave an alignment gap which is smaller, we can
	// trim a leading free block and release it back to the heap. We must
	// do this because the previous physical block is in use, therefore
	// the prev_phys_block field is not valid, and we can't simply adjust
	// the size of that block.
	//
	const size_t gap_minimum = sizeof(block_header_t);
	const size_t size_with_gap = adjust_request_size(adjust + align + gap_minimum, align);

	// If alignment is less than or equals base alignment, we're done.
	const size_t aligned_size = (align <= ALIGN_SIZE) ? adjust : size_with_gap;

	block_header_t* block = block_locate_free(pool, aligned_size);

	// This can't be a static assert.
	tlsf_assert(sizeof(block_header_t) == block_size_min + block_header_overhead);

	if (block) {
		void* ptr = block_to_ptr(block);
		void* aligned = align_ptr(ptr, align);
		size_t gap = tlsf_cast(size_t,
			tlsf_cast(tlsfptr_t, aligned) - tlsf_cast(tlsfptr_t, ptr));

		// If gap size is too small, offset to next aligned boundary.
		if (gap && gap < gap_minimum) {
			const size_t gap_remain = gap_minimum - gap;
			const size_t offset = tlsf_max(gap_remain, align);
			const void* next_aligned = tlsf_cast(void*,
				tlsf_cast(tlsfptr_t, aligned) + offset);

			aligned = align_ptr(next_aligned, align);
			gap = tlsf_cast(size_t,
				tlsf_cast(tlsfptr_t, aligned) - tlsf_cast(tlsfptr_t, ptr));
		}

		if (gap) {
			tlsf_assert(gap >= gap_minimum && "gap size too small");
			block = block_trim_free_leading(pool, block, gap);
		}
	}

	return block_prepare_used(pool, block, adjust);
}

void tlsf_free(tlsf_pool tlsf, void* ptr)
{
	// Don't attempt to free a NULL pointer.
	if (ptr) {
		pool_t* pool = tlsf_cast(pool_t*, tlsf);
		block_header_t* block = block_from_ptr(ptr);
		block_mark_as_free(block);
		block = block_merge_prev(pool, block);
		block = block_merge_next(pool, block);
		block_insert(pool, block);
	}
}

//
// The TLSF block information provides us with enough information to
// provide a reasonably intelligent implementation of realloc, growing or
// shrinking the currently allocated block as required.
//
// This routine handles the somewhat esoteric edge cases of realloc:
// - a non-zero size with a null pointer will behave like malloc
// - a zero size with a non-null pointer will behave like free
// - a request that cannot be satisfied will leave the original buffer
//   untouched
// - an extended buffer size will leave the newly-allocated area with
//   contents undefined
//
void* tlsf_realloc_aligned(tlsf_pool tlsf, void* ptr, size_t align, size_t size)
{
	pool_t* pool = tlsf_cast(pool_t*, tlsf);
	void* p = 0;

	// Zero-size requests are treated as free.
	if (ptr && size == 0) {
		tlsf_free(tlsf, ptr);
	}
	// Requests with NULL pointers are treated as malloc.
	else if (!ptr) {
		p = tlsf_memalign(tlsf, align, size);
	} else {
		block_header_t* block = block_from_ptr(ptr);
		block_header_t* next = block_next(block);

		const size_t cursize = block_size(block);
		const size_t combined = cursize + block_size(next) + block_header_overhead;
		const size_t adjust = adjust_request_size(size, ALIGN_SIZE);

		//
		// If the next block is used, or when combined with the current
		// block, does not offer enough space, we must reallocate and copy.
		// If wanted align is stricter then current align, reallocate and copy.
		//
		if ((adjust > cursize && (!block_is_free(next) || adjust > combined))
			 || (align_ptr(ptr, align) != ptr)
		   ) {
			p = tlsf_memalign(tlsf, align, size);
			if (p) {
				const size_t minsize = tlsf_min(cursize, size);
				tlsf_memcpy(p, ptr, minsize);
				tlsf_free(tlsf, ptr);
			}
		} else {
			// Do we need to expand to the next block?
			if (adjust > cursize) {
				block_merge_next(pool, block);
				block_mark_as_used(block);
			}
			// Trim the resulting block and return the original pointer.
			block_trim_used(pool, block, adjust);
			p = ptr;
		}
	}

	return p;
}

void* tlsf_realloc(tlsf_pool tlsf, void* ptr, size_t size)
{
	return tlsf_realloc_aligned(tlsf, ptr, ALIGN_SIZE, size);
}