C中的数组asm函数

时间:2014-02-07 00:55:01

标签: c assembly arm

如何在C中返回此数组asm函数的值?在这种情况下,我不确定如何使用sprintf。

我需要在显示中显示数组函数之前和之后的一些值。

//*****************************************************************************
//FUNCTION: InitXa
//DESCRIPTION: array X of size N with a constant value V, using pointers:
//PARAMETERS: r0 = *X
//            r1 = Size N
//            r2 = Value V
//RETURN: None
//*****************************************************************************

// local register definitions
#define        rXA        r0        // register to hold address of X
#define        rN    r1    // register to hold value of N
#define        rV    r2    // register to hold value of V

__asm void InitXa (uint32 *X, uint32 N, uint32 V)
{
    STR rN, [rXA]     ; Store the value at first address of array.
    SUBS rV, #1       ; decrement the count 
loop
    STR rN,[rXA],#4   ; Store the value and increment the pointer
    SUBS rV,rV,#1     ; decrement the count
    BNE loop          ; branch until the count is 0
    BX lr             ; return to caller
}

C部分代码:

uint32 X = {10, 2, 3};
uint32 N = 10;
uint32 V = 3;
uint32 result32;

sprintf (str, "%d", result32);    //  **display the first few values of the array before     initialization on the top line of the OLED.**

InitXa (X, N, V); 

sprintf (str, "%d", result32); //**Use the second line to display values after** initialization.

1 个答案:

答案 0 :(得分:0)

您似乎不熟悉如何访问数组元素。此外,未使用result32值,因此无需打印它。我认为这就是你的意图:

printf("Before calling asm function: %d, %d, %d \n", X[0], X[1], X[2]);

InitXa (X, N, V); 

printf("After calling asm function: %d, %d, %d \n", X[0], X[1], X[2]);

P.S。 - 我建议你读这本书: http://www.amazon.com/The-Programming-Language-Brian-Kernighan/dp/0131101633/ref=sr_1_2?ie=UTF8&qid=1391790669&sr=8-2&keywords=k%26r+the+c+programming+language

写作风格相当干燥,但它帮助我理解了30年前的C并且它今天同样有效。