/*
** Two Level Segregated Fit memory allocator, version 3.1.
** Written by Matthew Conte
**	http://tlsf.baisoku.org
**
** Based on the original documentation by Miguel Masmano:
**	http://www.gii.upv.es/tlsf/main/docs
**
** This implementation was written to the specification
** of the document, therefore no GPL restrictions apply.
**
** Copyright (c) 2006-2016, Matthew Conte
** All rights reserved.
**
** Redistribution and use in source and binary forms, with or without
** modification, are permitted provided that the following conditions are met:
**     * Redistributions of source code must retain the above copyright
**       notice, this list of conditions and the following disclaimer.
**     * Redistributions in binary form must reproduce the above copyright
**       notice, this list of conditions and the following disclaimer in the
**       documentation and/or other materials provided with the distribution.
**     * Neither the name of the copyright holder nor the
**       names of its contributors may be used to endorse or promote products
**       derived from this software without specific prior written permission.
**
** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
** ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
** WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
** DISCLAIMED. IN NO EVENT SHALL MATTHEW CONTE BE LIABLE FOR ANY
** DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
** (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
** ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
** SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

#pragma once

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

/*
** 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
*/
#define block_header_free_bit  (1 << 0)
#define 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.
*/
#define block_header_overhead  (sizeof(size_t))

/* User data starts directly after the size field in a used block. */
#define 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.
*/
#define block_size_min  (sizeof(block_header_t) - sizeof(block_header_t*))

/*
** block_header_t member functions.
*/
static inline __attribute__((__always_inline__)) size_t block_size(const block_header_t* block)
{
	return block->size & ~(block_header_free_bit | block_header_prev_free_bit);
}

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

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

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

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

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

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

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

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

static inline __attribute__((__always_inline__)) 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 inline __attribute__((__always_inline__)) 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 inline __attribute__((__always_inline__)) block_header_t* block_prev(const block_header_t* block)
{
	return block->prev_phys_block;
}

/* Return location of next existing block. */
static inline __attribute__((__always_inline__)) 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);
	return next;
}

/* Link a new block with its physical neighbor, return the neighbor. */
static inline __attribute__((__always_inline__)) 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 inline __attribute__((__always_inline__)) 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 inline __attribute__((__always_inline__)) 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);
}