; memory.asm — bump allocator via brk/mmap
%include "include/syscall.inc"
%include "include/memory.inc"

section .bss
align 16
heap_base: resq 1
heap_ptr:  resq 1
heap_end:  resq 1

section .text
global mem_init
global mem_alloc

; void mem_init()
mem_init:
    push rbp
    mov rbp, rsp
    ; brk(0) to get current break
    xor rdi, rdi
    mov rax, SYS_BRK
    syscall
    mov [rel heap_base], rax
    mov [rel heap_ptr], rax
    ; brk(base + HEAP_SIZE)
    add rax, HEAP_SIZE
    mov rdi, rax
    mov rax, SYS_BRK
    syscall
    mov [rel heap_end], rax
    pop rbp
    ret

; void* mem_alloc(size_t bytes) — bump allocator
mem_alloc:
    ; align to 8
    add rdi, 7
    and rdi, ~7
    mov rax, [rel heap_ptr]
    mov rcx, rax
    add rcx, rdi
    cmp rcx, [rel heap_end]
    jg .oom
    mov [rel heap_ptr], rcx
    ret
.oom:
    xor rax, rax
    ret