Rust f32 float fraction truncation

f32_trunc.rs

fn f32_to_f28(x: f32) -> f32 {
    let mut bytes = x.to_be_bytes();
    bytes[3] = bytes[3] & 0xF0;
    f32::from_be_bytes(bytes)
}

fn f32_to_f24(x: f32) -> f32 {
    let mut bytes = x.to_be_bytes();
    bytes[3] = 0;
    f32::from_be_bytes(bytes)
}

fn f32_to_f20(x: f32) -> f32 {
    let mut bytes = x.to_be_bytes();
    bytes[2] = bytes[2] & 0xF0;
    bytes[3] = 0;
    f32::from_be_bytes(bytes)
}

fn f32_to_f16(x: f32) -> f32 {
    let mut bytes = x.to_be_bytes();
    bytes[2] = 0;
    bytes[3] = 0;
    f32::from_be_bytes(bytes)
}

fn f32_to_f12(x: f32) -> f32 {
    let mut bytes = x.to_be_bytes();
    bytes[1] = bytes[1] & 0xF0;
    bytes[2] = 0;
    bytes[3] = 0;
    f32::from_be_bytes(bytes)
}

fn f32_to_f10(x: f32) -> f32 {
    let mut bytes = x.to_be_bytes();
    bytes[1] = bytes[1] & 0x80;
    bytes[2] = 0;
    bytes[3] = 0;
    f32::from_be_bytes(bytes)
}

fn main() {
    let original = std::f32::consts::PI;
    let truncated_28 = f32_to_f28(original);
    let truncated_24 = f32_to_f24(original);
    let truncated_20 = f32_to_f20(original);
    let truncated_16 = f32_to_f16(original);
    let truncated_12 = f32_to_f12(original);
    let truncated_10 = f32_to_f10(original);

    println!("f32: {:#034b} | {:08X} => {}", original.to_bits(), original.to_bits(), original);
    println!("f28: {:#034b} | {:08X} => {}", truncated_28.to_bits(), truncated_28.to_bits(), truncated_28);
    println!("f24: {:#034b} | {:08X} => {}", truncated_24.to_bits(), truncated_24.to_bits(), truncated_24);
    println!("f20: {:#034b} | {:08X} => {}", truncated_20.to_bits(), truncated_20.to_bits(), truncated_20);
    println!("f16: {:#034b} | {:08X} => {}", truncated_16.to_bits(), truncated_16.to_bits(), truncated_16);
    println!("f12: {:#034b} | {:08X} => {}", truncated_12.to_bits(), truncated_12.to_bits(), truncated_12);
    println!("f10: {:#034b} | {:08X} => {}", truncated_10.to_bits(), truncated_10.to_bits(), truncated_10);

}