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Юрий
Asked:2020-07-10 17:27:55 +0000 UTC2020-07-10 17:27:55 +0000 UTC

将 N 个连续位分配为一个变量

  • 772

是否可以像使用 N 位的连续序列一样选择和处理纯 SI。N 大于 64。我设法分配的最大数量是 unsigned long long - 8 字节或 double - 10 字节。但这对我来说还不够。我需要共同存储约 150 位的数据，并使用按位运算来获取和放置值。如果您分配为指向某种类型的指针，那么您不能立即获得一整套位。在位域的帮助下，它也不起作用，因为您不能将它们顺序传递给函数。

c

2 个回答

  1. Best Answer

    你为什么不喜欢这样的东西？

    typedef struct { unsigned char b[32]; } bitfield;

void zero(bitfield*b)
{
    memset(b->b,0,sizeof(*b));
}

void set(bitfield*b, int i)
{
    int idx = i/8;
    unsigned char mask = 1 << i%8;
    b->b[idx] |= mask;
}

int get(bitfield*b, int i)
{
    int idx = i/8;
    return (b->b[idx] >> i%8)&0x01;
}

int main()
{
    bitfield b;
    zero(&b);
    set(&b,15);
    set(&b,2);
    printf("%d - %d, %d - %d, %d - %d, %d - %d\n",
           2,  get(&b,2),  10,get(&b,10),
           12, get(&b,12), 15,get(&b,15));
}

    编写其他函数不是问题...通过将常量 32 更改为所需的函数来缩放:)

    • 3

  2. 顺便说一句，一切都是通过将字段“推”到 ull 来决定的。不是很通用，但很有效。unsigned long long *data 这是一个包含两个元素的数组

    #define OILPressusreMask 0xF000000000000000;
#define OILTemperatureMask 0x0FE0000000000000;
#define FuelTemperatureMask 0x001FC00000000000;
#define FuelMassMask 0x00003FC000000000;
#define XMask 0x0000003FFF000000;
#define YMask 0x0000000000FFFC00;
#define mmMask 0x001FC000000003F0;
#define hhMask 0x001FC0000000000F;

#define RPMMask 0xFFF0000000000000;
#define ZMask 0x000FFFC000000000;
#define VelocityMask 0x0000003FE0000000;
#define HVelocityMask 0x000000001F000000;
#define AzimuthMask  0x0000000000FF8000;
#define HorizontMask 0x0000000000007FC0;
#define ssMask 0x000000000000003F;


struct U2
{
    // First 64 bits (8 bytes)
    unsigned long long OilPressure:4;
    unsigned long long OilTemperature:7;
    unsigned long long FuelTemperature:7;
    unsigned long long FuelMass:8;
    unsigned long long X:14;
    unsigned long long Y:14;
    unsigned long long mm:6;
    unsigned long long hh:4;
    
    // Second 64 bits (8 bytes)
    unsigned long long RPM:12;
    unsigned long long Z:14;
    unsigned long long Velocity:9;
    unsigned long long HVelocity:5;
    unsigned long long Azimuth:9;
    unsigned long long Horizont: 9;
    unsigned long long ss:6;
};

unsigned short packTo2LongLongInt( unsigned long long *data, struct U2 *aircraft)
{
    // Проверка на валидность данных. Коды ошибок подразумеваются......
    data[0] = 0; data[1] = 0;
    data[0] = aircraft->OilPressure;
    data[0] <<= 7;
    data[0] |= aircraft->OilTemperature;
    data[0] <<= 7;
    data[0] |= aircraft->FuelTemperature;
    data[0] <<= 8;
    data[0] |= aircraft->FuelMass;
    data[0] <<= 14;
    data[0] |= aircraft->X;
    data[0] <<= 14;
    data[0] |= aircraft->Y;
    data[0] <<= 6;
    data[0] |= aircraft->mm;
    data[0] <<= 4;
    data[0] |= aircraft->hh;
    
    #if defined(DEBUG)
        printf("Первые 64 бит упакованы успешно; ");
    #endif
    
    data[1] |= aircraft->RPM;
    data[1] <<= 14;
    data[1] |= aircraft->Z;
    data[1] <<= 9;
    data[1] |= aircraft->Velocity;
    data[1] <<= 5;
    data[1] |= aircraft->HVelocity;
    data[1] <<= 9;
    data[1] |= aircraft->Azimuth;
    data[1] <<= 9;
    data[1] |= aircraft->Horizont;
    data[1] <<= 6;
    data[1] |= aircraft->ss;
    
    #if defined(DEBUG)
        printf("Вторые 64 бит упакованы успешно; Упаковка завершена\n");
    #endif

    return 0;
}

unsigned short unpackFrom2LongLongInt( unsigned long long *data, struct U2 *aircraft)
{
    unsigned long long tmp;
    unsigned char i = 60;
    
    tmp = data[0] & OILPressusreMask;
    tmp >>= i;
    aircraft->OilPressure = tmp;
    
    i-=7;
    tmp = data[0] & OILTemperatureMask;
    tmp >>= i;
    aircraft->OilTemperature = tmp;
    
    i -= 7;
    tmp = data[0] & FuelTemperatureMask;
    tmp >>= i;
    aircraft->FuelTemperature = tmp;

    i -= 8;
    tmp = data[0] & FuelMassMask;
    tmp >>= i;
    aircraft->FuelMass = tmp;

    i -= 14;
    tmp = data[0] & XMask;
    tmp >>= i;
    aircraft->X = tmp;
    
    i -= 14;
    tmp = data[0] & YMask;
    tmp >>= i;
    aircraft->Y = tmp;

    i -= 6;
    tmp = data[0] & mmMask;
    tmp >>= i;
    aircraft->mm = tmp;

    i -= 4;
    tmp = data[0] & hhMask;
    tmp >>= i;
    aircraft->hh = tmp;

    i = 64-12;
    tmp = data[1] & RPMMask;
    tmp >>= i;
    aircraft->RPM = tmp;

    i -= 14;
    tmp = data[1] & ZMask;
    tmp >>= i;
    aircraft->Z = tmp;

    i -= 9;
    tmp = data[1] & VelocityMask;
    tmp >>= i;
    aircraft->Velocity = tmp;

    i -= 5;
    tmp = data[1] & HVelocityMask;
    tmp >>= i;
    aircraft->HVelocity = tmp;

    i -= 9;
    tmp = data[1] & AzimuthMask;
    tmp >>= i;
    aircraft->Azimuth = tmp;

    i -= 9;
    tmp = data[1] & HorizontMask;
    tmp >>= i;
    aircraft->Horizont = tmp;

    i -= 6;
    tmp = data[1] & ssMask;
    tmp >>= i;
    aircraft->ss = tmp;
    
    #if defined(DEBUG)
        printf("Данные распакованы\n");
    #endif

    return 0;
}
    • 0

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