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) return -1; 
    if (ctrl->parity_enable == 0) return data;
    int count = 0; 

    // count 1s
    for (int i = 0; i < 7; i++) // only count from 0 to 6 since 7 is parity bit
    {
        count += (data >> i) & 1;  
    }

    // check parity enable
    int parity_bit = 0; 
    if (ctrl->parity_type == 0) // even parity type
    {
        if (count & 1) // 1s are odd
        {
            parity_bit = 1; 
        }
        else // 1s are even
        {
            parity_bit = 0; 
        }
    }
    else                        // odd parity type
    {
        if (count & 1) // 1s are odd
        {
            parity_bit = 0; 
        }
        else // 1s are even
        {
            parity_bit = 1; 
        }
    }

    // assign parity bit
    if (parity_bit == 1)
    {
        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