#include <errno.h>
#include <stdint.h>

static uint8_t *__sbrk_heap_end = NULL;

void *_sbrk(ptrdiff_t incr)
{
	extern uint8_t _end; /* Symbol defined in the linker script */
	extern uint8_t _estack; /* Symbol defined in the linker script */
	extern uint32_t _Min_Stack_Size; /* Symbol defined in the linker script */
	const uint32_t stack_limit = (uint32_t)&_estack - (uint32_t)&_Min_Stack_Size;
	const uint8_t *max_heap = (uint8_t *)stack_limit;
	uint8_t *prev_heap_end;

	if (NULL == __sbrk_heap_end) {
		__sbrk_heap_end = &_end;
	}

	if (__sbrk_heap_end + incr > max_heap) {
		errno = ENOMEM;
		return (void *)-1;
	}

	prev_heap_end = __sbrk_heap_end;
	__sbrk_heap_end += incr;

	return (void *)prev_heap_end;
}