; utils/parse.asm - decimal parsing helper.

section .text

; parse_u64: read decimal digits at [RSI] into RAX, advancing RSI past them.
; Stops on the first non-digit. Clobbers RAX, RDX.
parse_u64:
    xor     rax, rax
.digit:
    mov     dl, [rsi]
    cmp     dl, '0'
    jl      .done
    cmp     dl, '9'
    jg      .done
    sub     dl, '0'
    movzx   rdx, dl
    imul    rax, rax, 10
    add     rax, rdx
    inc     rsi
    jmp     .digit
.done:
    ret