Construct UART Data Frame with Parity Bit

Code

#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) {
        uint8_t cnt = 0;
        uint8_t set = 0;
        uint8_t tmp = ((1 << 7) - 1) & data;
        /* count number of 1 */
        while (tmp) {
            if (tmp & 0x1)
                cnt++;
            tmp >>= 1;
        }
        if (ctrl->parity_type) {
            /* 1: odd */
            set = (cnt & 0x1) ? 0 : 1;
        } else {
            /* 0: even */
            set = (cnt & 0x1) ? 1 : 0;
        }
        if (set)
            data |= (1 << 7);
        else
            data &= ~(1 << 7);
    }
    return 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;
}

Solving Approach