tlsf.c

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#include <assert.h>
#include <limits.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.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
{
#if defined (TLSF_64BIT)
        /* All allocation sizes and addresses are aligned to 8 bytes. */
        ALIGN_SIZE_LOG2 = 3,
#else
        /* All allocation sizes and addresses are aligned to 4 bytes. */
        ALIGN_SIZE_LOG2 = 2,
#endif
        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.
        */
 
#if defined (TLSF_64BIT)
        /*
        ** TODO: We can increase this to support larger sizes, at the expense
        ** of more overhead in the TLSF structure.
        */
        FL_INDEX_MAX = 32,
#else
        FL_INDEX_MAX = 30,
#endif
        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]
 
/* 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 control structure. */
typedef struct control_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];
} control_t;
 
/* A type used for casting when doing pointer arithmetic. */
typedef ptrdiff_t tlsfptr_t;
 
/*
** 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(control_t* control, 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 = control->sl_bitmap[fl] & (~0 << sl);
        if (!sl_map)
        {
                /* No block exists. Search in the next largest first-level list. */
                const unsigned int fl_map = control->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 = control->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 control->blocks[fl][sl];
}
 
/* Remove a free block from the free list.*/
static void remove_free_block(control_t* control, 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 (control->blocks[fl][sl] == block)
        {
                control->blocks[fl][sl] = next;
 
                /* If the new head is null, clear the bitmap. */
                if (next == &control->block_null)
                {
                        control->sl_bitmap[fl] &= ~(1 << sl);
 
                        /* If the second bitmap is now empty, clear the fl bitmap. */
                        if (!control->sl_bitmap[fl])
                        {
                                control->fl_bitmap &= ~(1 << fl);
                        }
                }
        }
}
 
/* Insert a free block into the free block list. */
static void insert_free_block(control_t* control, block_header_t* block, int fl, int sl)
{
        block_header_t* current = control->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 = &control->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.
        */
        control->blocks[fl][sl] = block;
        control->fl_bitmap |= (1 << fl);
        control->sl_bitmap[fl] |= (1 << sl);
}
 
/* Remove a given block from the free list. */
static void block_remove(control_t* control, block_header_t* block)
{
        int fl, sl;
        mapping_insert(block_size(block), &fl, &sl);
        remove_free_block(control, block, fl, sl);
}
 
/* Insert a given block into the free list. */
static void block_insert(control_t* control, block_header_t* block)
{
        int fl, sl;
        mapping_insert(block_size(block), &fl, &sl);
        insert_free_block(control, 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(control_t* control, 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(control, 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(control_t* control, 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(control, 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(control_t* control, 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(control, remaining_block);
        }
}
 
/* Trim any trailing block space off the end of a used block, return to pool. */
static void block_trim_used(control_t* control, 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(control, remaining_block);
                block_insert(control, remaining_block);
        }
}
 
static block_header_t* block_trim_free_leading(control_t* control, 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(control, block);
        }
 
        return remaining_block;
}
 
static block_header_t* block_locate_free(control_t* control, size_t size)
{
        int fl = 0, sl = 0;
        block_header_t* block = 0;
 
        if (size)
        {
                mapping_search(size, &fl, &sl);
                block = search_suitable_block(control, &fl, &sl);
                if(block && !block->size)
                        block = NULL;
 
        }
 
        if (block)
        {
                tlsf_assert(block_size(block) >= size);
                remove_free_block(control, block, fl, sl);
        }
 
        return block;
}
 
static void* block_prepare_used(control_t* control, block_header_t* block, size_t size)
{
        void* p = 0;
        if (block)
        {
                block_trim_free(control, 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 control_construct(control_t* control)
{
        int i, j;
 
        control->block_null.next_free = &control->block_null;
        control->block_null.prev_free = &control->block_null;
 
        control->fl_bitmap = 0;
        for (i = 0; i < FL_INDEX_COUNT; ++i)
        {
                control->sl_bitmap[i] = 0;
                for (j = 0; j < SL_INDEX_COUNT; ++j)
                {
                        control->blocks[i][j] = &control->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(tlsf_t tlsf)
{
        int i, j;
 
        control_t* control = tlsf_cast(control_t*, tlsf);
        int status = 0;
 
        /* 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 = control->fl_bitmap & (1 << i);
                        const int sl_list = control->sl_bitmap[i];
                        const int sl_map = sl_list & (1 << j);
                        const block_header_t* block = control->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 == &control->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 != &control->block_null && "block should not be null");
 
                        while (block != &control->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)
{
        (void)user;
        printf("\t%p %s size: %x (%p)\n", ptr, used ? "used" : "free", (unsigned int)size, block_from_ptr(ptr));
}
 
void tlsf_walk_pool(pool_t pool, tlsf_walker walker, void* user)
{
        tlsf_walker pool_walker = walker ? walker : default_walker;
        block_header_t* block =
                offset_to_block(pool, -(int)block_header_overhead);
 
        while (block && !block_is_last(block))
        {
                pool_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;
}
 
int tlsf_check_pool(pool_t pool)
{
        /* Check that the blocks are physically correct. */
        integrity_t integ = { 0, 0 };
        tlsf_walk_pool(pool, integrity_walker, &integ);
 
        return integ.status;
}
 
/*
** Size of the TLSF structures in a given memory block passed to
** tlsf_create, equal to the size of a control_t
*/
size_t tlsf_size()
{
        return sizeof(control_t);
}
 
size_t tlsf_align_size()
{
        return ALIGN_SIZE;
}
 
size_t tlsf_block_size_min()
{
        return block_size_min;
}
 
size_t tlsf_block_size_max()
{
        return block_size_max;
}
 
/*
** Overhead of the TLSF structures in a given memory block passes to
** tlsf_add_pool, equal to the overhead of a free block and the
** sentinel block.
*/
size_t tlsf_pool_overhead()
{
        return 2 * block_header_overhead;
}
 
size_t tlsf_alloc_overhead()
{
        return block_header_overhead;
}
 
pool_t tlsf_add_pool(tlsf_t tlsf, void* mem, size_t bytes)
{
        block_header_t* block;
        block_header_t* next;
 
        const size_t pool_overhead = tlsf_pool_overhead();
        const size_t pool_bytes = align_down(bytes - pool_overhead, ALIGN_SIZE);
 
        if (((ptrdiff_t)mem % ALIGN_SIZE) != 0)
        {
                printf("tlsf_add_pool: Memory must be aligned by %u bytes.\n",
                        (unsigned int)ALIGN_SIZE);
                return 0;
        }
 
        if (pool_bytes < block_size_min || pool_bytes > block_size_max)
        {
#if defined (TLSF_64BIT)
                printf("tlsf_add_pool: Memory size must be between 0x%x and 0x%x00 bytes.\n", 
                        (unsigned int)(pool_overhead + block_size_min),
                        (unsigned int)((pool_overhead + block_size_max) / 256));
#else
                printf("tlsf_add_pool: Memory 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;
        }
 
        /*
        ** Create the main free block. Offset the start of the block slightly
        ** so that the prev_phys_block field falls outside of the pool -
        ** it will never be used.
        */
        block = offset_to_block(mem, -(tlsfptr_t)block_header_overhead);
        block_set_size(block, pool_bytes);
        block_set_free(block);
        block_set_prev_used(block);
        block_insert(tlsf_cast(control_t*, tlsf), block);
 
        /* Split the block to create a zero-size sentinel block. */
        next = block_link_next(block);
        block_set_size(next, 0);
        block_set_used(next);
        block_set_prev_free(next);
 
        return mem;
}
 
void tlsf_remove_pool(tlsf_t tlsf, pool_t pool)
{
        control_t* control = tlsf_cast(control_t*, tlsf);
        block_header_t* block = offset_to_block(pool, -(int)block_header_overhead);
 
        int fl = 0, sl = 0;
 
        tlsf_assert(block_is_free(block) && "block should be free");
        tlsf_assert(!block_is_free(block_next(block)) && "next block should not be free");
        tlsf_assert(block_size(block_next(block)) == 0 && "next block size should be zero");
 
        mapping_insert(block_size(block), &fl, &sl);
        remove_free_block(control, block, fl, sl);
}
 
/*
** TLSF main interface.
*/
 
#if _DEBUG
int test_ffs_fls()
{
        /* Verify ffs/fls work properly. */
        int rv = 0;
        rv += (tlsf_ffs(0) == -1) ? 0 : 0x1;
        rv += (tlsf_fls(0) == -1) ? 0 : 0x2;
        rv += (tlsf_ffs(1) == 0) ? 0 : 0x4;
        rv += (tlsf_fls(1) == 0) ? 0 : 0x8;
        rv += (tlsf_ffs(0x80000000) == 31) ? 0 : 0x10;
        rv += (tlsf_ffs(0x80008000) == 15) ? 0 : 0x20;
        rv += (tlsf_fls(0x80000008) == 31) ? 0 : 0x40;
        rv += (tlsf_fls(0x7FFFFFFF) == 30) ? 0 : 0x80;
 
#if defined (TLSF_64BIT)
        rv += (tlsf_fls_sizet(0x80000000) == 31) ? 0 : 0x100;
        rv += (tlsf_fls_sizet(0x100000000) == 32) ? 0 : 0x200;
        rv += (tlsf_fls_sizet(0xffffffffffffffff) == 63) ? 0 : 0x400; 
#endif
 
        if (rv)
        {
                printf("tlsf_create: %x ffs/fls tests failed!\n", rv);
        }
        return rv;
}
#endif
 
tlsf_t tlsf_create(void* mem)
{
#if _DEBUG
        if (test_ffs_fls())
        {
                return 0;
        }
#endif
 
        if (((tlsfptr_t)mem % ALIGN_SIZE) != 0)
        {
                printf("tlsf_create: Memory must be aligned to %u bytes.\n",
                        (unsigned int)ALIGN_SIZE);
                return 0;
        }
 
        control_construct(tlsf_cast(control_t*, mem));
 
        return tlsf_cast(tlsf_t, mem);
}
 
tlsf_t tlsf_create_with_pool(void* mem, size_t bytes)
{
        tlsf_t tlsf = tlsf_create(mem);
        tlsf_add_pool(tlsf, (char*)mem + tlsf_size(), bytes - tlsf_size());
        return tlsf;
}
 
void tlsf_destroy(tlsf_t tlsf)
{
        /* Nothing to do. */
        (void)tlsf;
}
 
pool_t tlsf_get_pool(tlsf_t tlsf)
{
        return tlsf_cast(pool_t, (char*)tlsf + tlsf_size());
}
 
void* tlsf_malloc(tlsf_t tlsf, size_t size)
{
        control_t* control = tlsf_cast(control_t*, tlsf);
        const size_t adjust = adjust_request_size(size, ALIGN_SIZE);
        block_header_t* block = block_locate_free(control, adjust);
        return block_prepare_used(control, block, adjust);
}
 
void* tlsf_memalign(tlsf_t tlsf, size_t align, size_t size)
{
        control_t* control = tlsf_cast(control_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 pool. 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(control, 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(control, block, gap);
                }
        }
 
        return block_prepare_used(control, block, adjust);
}
 
void tlsf_free(tlsf_t tlsf, void* ptr)
{
        /* Don't attempt to free a NULL pointer. */
        if (ptr)
        {
                control_t* control = tlsf_cast(control_t*, tlsf);
                block_header_t* block = block_from_ptr(ptr);
                tlsf_assert(!block_is_free(block) && "block already marked as free");
                block_mark_as_free(block);
                block = block_merge_prev(control, block);
                block = block_merge_next(control, block);
                block_insert(control, 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_t tlsf, void* ptr, size_t size)
{
        control_t* control = tlsf_cast(control_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);
 
                tlsf_assert(!block_is_free(block) && "block already marked as free");
 
                /*
                ** 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(control, block);
                                block_mark_as_used(block);
                        }
 
                        /* Trim the resulting block and return the original pointer. */
                        block_trim_used(control, block, adjust);
                        p = ptr;
                }
        }
 
        return p;
}