编写一个结构体合并函数从struct STRUCT_BITS { Uint16 bit1:1; Uint16 bit2:1; Uint16 bit3:1; Uint16 bit4:1; Uint16 bit5:1; Uint16 bit6:1; Uint16 bit7:1; Uint16 bit8:1; Uint16 bit9:1; Uint16 bit10:1; Uint16 bit11:1; Uint16 bit12:1; Uint16 bit13:1; Uint16 bit14:1; Uint16 bit15:1; Uint16 bit16:1; }; union Uint16_BIT_STRUCT { Uint16 all; struct STRUCT_BITS bit; };中实现随意取addr_a的bit1-4或bit2-3

可以使用位域来实现结构体合并函数，具体代码如下：

#include <stdio.h>

typedef unsigned short Uint16;

struct STRUCT_BITS {
    Uint16 bit1:1;
    Uint16 bit2:1;
    Uint16 bit3:1;
    Uint16 bit4:1;
    Uint16 bit5:1;
    Uint16 bit6:1;
    Uint16 bit7:1;
    Uint16 bit8:1;
    Uint16 bit9:1;
    Uint16 bit10:1;
    Uint16 bit11:1;
    Uint16 bit12:1;
    Uint16 bit13:1;
    Uint16 bit14:1;
    Uint16 bit15:1;
    Uint16 bit16:1;
};

union Uint16_BIT_STRUCT {
    Uint16 all;
    struct STRUCT_BITS bit;
};

void merge_struct(union Uint16_BIT_STRUCT* dest, union Uint16_BIT_STRUCT* src, int start, int end) {
    int i;
    for (i = start; i <= end; i++) {
        switch (i) {
            case 1:
                dest->bit.bit1 = src->bit.bit1;
                break;
            case 2:
                dest->bit.bit2 = src->bit.bit2;
                break;
            case 3:
                dest->bit.bit3 = src->bit.bit3;
                break;
            case 4:
                dest->bit.bit4 = src->bit.bit4;
                break;
            case 5:
                dest->bit.bit5 = src->bit.bit5;
                break;
            case 6:
                dest->bit.bit6 = src->bit.bit6;
                break;
            case 7:
                dest->bit.bit7 = src->bit.bit7;
                break;
            case 8:
                dest->bit.bit8 = src->bit.bit8;
                break;
            case 9:
                dest->bit.bit9 = src->bit.bit9;
                break;
            case 10:
                dest->bit.bit10 = src->bit.bit10;
                break;
            case 11:
                dest->bit.bit11 = src->bit.bit11;
                break;
            case 12:
                dest->bit.bit12 = src->bit.bit12;
                break;
            case 13:
                dest->bit.bit13 = src->bit.bit13;
                break;
            case 14:
                dest->bit.bit14 = src->bit.bit14;
                break;
            case 15:
                dest->bit.bit15 = src->bit.bit15;
                break;
            case 16:
                dest->bit.bit16 = src->bit.bit16;
                break;
            default:
                break;
        }
    }
}

int main() {
    union Uint16_BIT_STRUCT a, b;

    a.all = 0b1111000000000000; // 0xF000
    b.all = 0b0000000000001100; // 0x000C

    merge_struct(&a, &b, 1, 4); // 取bit1-4
    printf("0x%04X\n", a.all); // 输出 0xF00C

    a.all = 0b1111000000000000; // 0xF000
    b.all = 0b0000000000000110; // 0x0006

    merge_struct(&a, &b, 2, 3); // 取bit2-3
    printf("0x%04X\n", a.all); // 输出 0xF006

    return 0;
}

在 `merge_struct` 函数中，使用 `switch` 语句将需要合并的位域一个一个赋值给目标结构体。可以通过传入的参数 `start` 和 `end` 来指定需要合并的位域。

在 `main` 函数中，先初始化两个结构体 `a` 和 `b`，然后分别通过 `merge_struct` 函数合并指定的位域，最后输出合并后的结果。

注意，上面的代码中使用了二进制字面量，需要使用 C99 标准或更高版本的编译器才能编译通过。如果编译器不支持二进制字面量，可以使用十六进制字面量替代。