#include <assert.h>
#include <stddef.h>   /* NULL, size_t */
#include <stdint.h>   /* uintptr_t */
#include <sys/mman.h> /* mmap */

#ifndef MEMSIZE
#define MEMSIZE 1024*4*1024*1024l
#endif

#define unlikely(x)     __builtin_expect((x),0)

#ifdef __cplusplus
extern "C" {
#endif

typedef struct bumpptr {
	uintptr_t end;
	uintptr_t ptr;
} bumpptr_t;

__thread bumpptr_t* tsd = NULL;

static inline void* bump_up(size_t size, size_t align) {
	assert(align % 2 == 0);

	if (unlikely(tsd == NULL)) {
		void* mem_start = mmap(NULL, MEMSIZE, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
		if(mem_start == MAP_FAILED) {
			perror("mmap");
			return NULL;
		}
		tsd = (bumpptr_t*)mem_start;
		tsd->ptr = (uintptr_t)mem_start + sizeof(bumpptr_t);
		tsd->end = (uintptr_t)mem_start + MEMSIZE;
	}

	// align ptr;
	uintptr_t aligned = (tsd->ptr + align - 1) & ~(align - 1);

	uintptr_t new_ptr = aligned + size;
	if (new_ptr > tsd->end)
		return NULL;
	else {
		tsd->ptr = new_ptr;
		return (void*)aligned;
	}
}

#ifdef __cplusplus
}
#endif