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) {
    if (!ctrl->parity_enable) {
        return data;   
    }

    int count = 0;
    uint8_t temp = data;

    // count number of 1s
    while (temp) {
        count += temp & 1;
        temp >>= 1;
    }

    uint8_t parity_bit;

    if (ctrl->parity_type == 0) {     // Even parity
        parity_bit = (count % 2);
    } 
    else {                         // Odd parity
        parity_bit = !(count % 2);
    }

    return (parity_bit << 7) | data;
    
}

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;
}