#ifndef LALLOC_H_
#define LALLOC_H_

#include <stdint.h>
#include <stddef.h>

#ifdef __ccplusplus
extern "C" {
#endif

// Internal header added in front of each allocation
typedef struct BlockHeader BlockHeader;
struct BlockHeader {
    uint32_t next;            // offset from base
    uint32_t prev;            // offset from base
    uint32_t size_and_flags;  // size | free_bit
    // Padding to ensure we always return 16 byte aligned pointers.
    uint8_t pad[4];
};
_Static_assert(sizeof(BlockHeader) == 16, "sizeof(BlockHeader) is not 16");

/**
 * General purpose allocator.
 * - Allocated pointers are aligned to 16 bytes.
 * - Backing buffer must be aligned to 16 bytes start
 * - 4Gb - 16 is max for the allocator backing buffer.
 * - Allocation of > 0 bytes returns a size aligned up to 16 bytes
 * - Allocation of 0 bytes returns a valid pointer with 0 usable space
 * The allocator maintains a doubly linked list of blocks,
 * when blocks are free'd, adjacent blocks are merged to keep
 * fragmentation to a minimum
 */
typedef struct LAlloc LAlloc;
struct LAlloc {
    uint8_t *base;            // backing store
    uint32_t size;            // total size
    BlockHeader *heap_start;  // first block
    BlockHeader *next_alloc;  // start of free block search
};

void lalloc_init(LAlloc *allocator, void *backing_store, uint32_t size);

void *lalloc(LAlloc *allocator, uint32_t size);
void lfree(LAlloc *allocator, void *ptr);

BlockHeader *block_from_offset(const LAlloc *allocator, uint32_t offset);
uint32_t block_size(const BlockHeader *block);
int block_is_free(const BlockHeader *block);

#ifdef __ccplusplus
}  // extern "C"
#endif
#endif