76. Construct UART Data Frame with Parity Bit

#include <stdio.h>
#include <stdint.h>

typedef struct {
    uint8_t parity_enable : 1;
    uint8_t parity_type   : 1;
    uint8_t reserved      : 6;
} UART_Control;

uint8_t create_uart_frame(uint8_t data, UART_Control *ctrl) 
{
    data &= 0x7F;
    if (ctrl->parity_enable == 0)
    {
        return data;
    }
    uint8_t p = data;
    uint8_t cnt = 0;

    while (p)
    {
        p &= (p - 1u);
        cnt++;
    }
    
    uint8_t parity_bit = (cnt & 1u) ^ ctrl->parity_type;
    return data | (parity_bit << 7);
}

int main() {
    uint8_t data;
    scanf("%hhu", &data);  // 7-bit input

    uint8_t parity_enable, parity_type;
    scanf("%hhu %hhu", &parity_enable, &parity_type);

    UART_Control ctrl;
    ctrl.parity_enable = parity_enable;
    ctrl.parity_type = parity_type;

    uint8_t frame = create_uart_frame(data, &ctrl);
    printf("frame = 0x%02X", frame);

    return 0;
}