Construct UART Data Frame with Parity Bit

Code

#include <stdint.h>
#include <stdio.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 & ~(1 << 7);
  } else {

    int c = 0;
    uint8_t tmp = data;

    while (tmp != 0) {

      if ((tmp & 1) != 0) {
        c += 1;
      }

      tmp >>= 1;
    }

    uint8_t parity_bit = 0;

    if (ctrl->parity_type == 0) {
      if (c % 2 == 0) {
        parity_bit = 0;
      } else {
        parity_bit = 1;
      }
    } else {
      if (c % 2 == 0) {
        parity_bit = 1;
      } else {
        parity_bit = 0;
      }
    }
    data &= ~(1 << 7);
    data |= (parity_bit << 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