如何将一个 16 位数字分解为两个 8 位数字？

Question

I have this piece of code in C and I want in nasm, decompose the 16bit to two 8bits, How Can I do it? C

uint16_t data = 0xCAFE; // global
uint8_t result[2];
...

decompose();
printf(
  "result %d %d \n", 
  result[0], result[1]
);

ASM

 global decompose
decompose:
  enter 0,0
  movzx ax, word[data],
  movzx al, [ax]
  leave
  ret

Answer 1

first: it is very bad design to create functions that have global side effects eg get their arguments or pass their results via globals.
second: there is absolutely no reason to use assembly on this. especially not if you pass the result to comparable slow printing routines.

If you really want to have functions for that I would suggest to introduce small inline functions

static inline uint8_t u16High(uint16_t v){ return (uint8_t)(v >> 8); }
static inline uint8_t u16Low (uint16_t v){ return (uint8_t)(v);      }

Another (in my eyes ugly) option would be:

static inline uint8_t* u16decompose(uint16_t* v){ return (uint8_t*)v; }

But beware: this only is allowed for uint8_t* you may not use this for 'decompose' uint32_t into uint16_t because this violates the strict aliasing rule.