c++ - C/C++ 更好的写法？

Question

我正在尝试编写易于调试的代码。有没有更好的方法来编写函数do_save():

int one;
int two[10];
char three;

...

unsigned char *state = (unsigned char*)malloc(1024);

...

void do_save()
{
    memcpy(state, &one, 4);
    memcpy(state+4, two, 40);
    memcpy(state+44, &three, 1);
}

当我说更好时，我指的是一种避免产生错误的方法，因为我弄乱了大小计数，尤其是当有 10 或 20 个变量要保存在状态中时。

Answer 1

使用结构。

int one;
int two[10];
char three;
typedef struct {
    int one;
    int two[10];
    char three;
} State;

...

State *state = new State; // C++ish
State *state = malloc(sizeof(State));  //Cish

...

void do_save(State* state) {
    state->one = &one;
    memcpy(state->two, &two, sizeof(state->two));
    state->three = three;
}

一旦有了结构，您就可以轻松地做很多事情。例如，您可以将当前状态和保存状态分开，保存/恢复可以用等号来完成。使用 fread/fwrite 写入二进制文件很容易。您可以根据需要将状态结构放在堆上或堆栈上。

#include <stdlib.h>
#include <stdio.h>

typedef struct {
    int one;
    int two[10];
    char three;
} State;

void print_state(State* state) {
    printf("%i ",   state->one);
    int i;
    for (i = 0; i < 10; ++i) {
        printf("%i ",   state->two[i]);
    }
    printf("%c\n",  state->three);
}

int main() {
    State* state = (State*)(malloc(sizeof(State)));
    State current_state;
    FILE* input = fopen("binary.data", "rb");
    if (input) {
        fread(&current_state, sizeof(State), 1, input);
        fclose(input);
    }

    print_state(&current_state);

    current_state.one = 1;
    int i;
    for (i = 0; i < 10; ++i) {
        current_state.two[i] = i + 1;
    }
    current_state.three = 'Z';
    *state = current_state;

    FILE* output = fopen("binary.data", "wb");
    fwrite(state, sizeof(State), 1, output);
    fclose(output);
        free(state);
}