Subversion Repositories freemyipod

#include "../../global.h"

#include "../include/assert.h"

#include <limits.h>

#include <stddef.h>

#include "../include/stdio.h"

#include "../include/stdlib.h"

#include "../include/string.h"

#include "../../console.h"

#include "../../thread.h"

#include "tlsf.h"

#include "tlsfbits.h"

/*

** Constants.

*/

/* 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),

	/*

	** We support 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 assert

#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]

/* FIXME: This code only currently supports 32-bit architectures. */

tlsf_static_assert(sizeof(size_t) * CHAR_BIT == 32);

/* 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);

/* sizeof fl_bitmap must be >= FL_INDEX_COUNT. */

tlsf_static_assert(sizeof(unsigned int) * CHAR_BIT >= FL_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 in the last word 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 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 = 1 << FL_INDEX_MAX;

/* Empty lists point at this block to indicate they are free. */

static block_header_t block_null;

/* The TLSF pool structure. */

typedef struct pool_t

{

	/* 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 unsigned int tlsfptr_t;

/*

** block_header_t member functions.

*/

static size_t block_size(const block_header_t* block) ICODE_ATTR;

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) ICODE_ATTR;

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) ICODE_ATTR;

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) ICODE_ATTR;

static int block_is_free(const block_header_t* block)

{

	return block->size & block_header_free_bit;

}

static void block_set_free(block_header_t* block) ICODE_ATTR;

static void block_set_free(block_header_t* block)

{

	block->size |= block_header_free_bit;

}

static void block_set_used(block_header_t* block) ICODE_ATTR;

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) ICODE_ATTR;

static int block_is_prev_free(const block_header_t* block)

{

	return block->size & block_header_prev_free_bit;

}

static void block_set_prev_free(block_header_t* block) ICODE_ATTR;

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) ICODE_ATTR;

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) ICODE_ATTR;

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) ICODE_ATTR;

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) ICODE_ATTR;

static block_header_t* offset_to_block(const void* ptr, size_t size)

{

	return tlsf_cast(block_header_t*,

		tlsf_cast(unsigned char*, ptr) + size);

}

/* Return location of previous block. */

static block_header_t* block_prev(const block_header_t* block) ICODE_ATTR;

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) ICODE_ATTR;

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) ICODE_ATTR;

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) ICODE_ATTR;

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) ICODE_ATTR;

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) ICODE_ATTR;

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) ICODE_ATTR;

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(void* ptr, size_t align) ICODE_ATTR;

static void* align_ptr(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) ICODE_ATTR;

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) ICODE_ATTR;

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 = size / (SMALL_BLOCK_SIZE / SL_INDEX_COUNT);

	}

	else

	{

		fl = tlsf_fls(size);

		sl = (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) ICODE_ATTR;

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(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) ICODE_ATTR;

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] & (0xffffffff << sl);

	if (!sl_map)

	{

		/* No block exists. Search in the next largest first-level list. */

		const unsigned int fl_map = pool->fl_bitmap & (0xffffffff << (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) ICODE_ATTR;

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 == &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) ICODE_ATTR;

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 = &block_null;

	current->prev_free = block;

	/*

	** 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) ICODE_ATTR;

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) ICODE_ATTR;

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) ICODE_ATTR;

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) ICODE_ATTR;

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_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) ICODE_ATTR;

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) ICODE_ATTR;

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) ICODE_ATTR;

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) ICODE_ATTR;

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) ICODE_ATTR;

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) ICODE_ATTR;

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) ICODE_ATTR;

static block_header_t* block_locate_free(pool_t* pool, size_t size)

{

	int fl, sl;

	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) ICODE_ATTR;

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) ICODE_ATTR;

static void pool_construct(pool_t* pool)

{

	int i, j;

	block_null.next_free = &block_null;

	block_null.prev_free = &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] = &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)

{

	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 == &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 != &block_null) && "block should not be null");

			while (block != &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 (used)

    {

        struct scheduler_thread* owner = *((struct scheduler_thread**)(ptr + size - 4));

        cprintf((int)user, "%08X: %08X+8 bytes owned by %08X%s\n", ptr,

                size - 4, owner, owner == current_thread ? " (self)" : "");

    }

    else cprintf((int)user, "%08X: %08X bytes free\n", ptr, size + 4);

}

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)

	{

		cprintf(CONSOLE_BOOT, "tlsf_create: Pool size must be between %d and %d bytes.\n", 

			pool_overhead + block_size_min, pool_overhead + block_size_max);

		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, align_down(pool_bytes, ALIGN_SIZE));

	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. */

	pool = 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 ptrdiff_t gap_minimum = tlsf_cast(ptrdiff_t, 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);

		ptrdiff_t gap = tlsf_cast(ptrdiff_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 ptrdiff_t gap_remain = gap_minimum - gap;

			const ptrdiff_t offset = tlsf_max(gap_remain, tlsf_cast(ptrdiff_t, align));

			void* next_aligned = tlsf_cast(void*,

				tlsf_cast(tlsfptr_t, aligned) + tlsf_cast(tlsfptr_t, offset));

			aligned = align_ptr(next_aligned, align);

			gap = tlsf_cast(ptrdiff_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(tlsf_pool tlsf, void* ptr, 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_malloc(tlsf, 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 (adjust > cursize && (!block_is_free(next) || adjust > combined))

		{

			p = tlsf_malloc(tlsf, size);

			if (p)

			{

				const size_t minsize = tlsf_min(cursize, size);

				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;

}