Bitwise Ops

// Bit flags built from the bitwise operators: `<<`, `|`, `&`, `^`.
//
// Each step prints the permission word it produced, in decimal and in binary,
// so the mask arithmetic is legible rather than implied.

func is_flag_set(flags: i32, mask: i32) -> bool {
    return (flags & mask) != 0
}

func set_flag(flags: i32, mask: i32) -> i32 {
    return flags | mask
}

func toggle_flag(flags: i32, mask: i32) -> i32 {
    return flags ^ mask
}

func main() -> i32 {
    val READ:    i32 = 1 << 0   // 0b001 = 1
    val WRITE:   i32 = 1 << 1   // 0b010 = 2
    val EXECUTE: i32 = 1 << 2   // 0b100 = 4

    mut perms: i32 = 0

    perms = set_flag(perms, READ)
    println("set READ    -> {perms:03b}")
    perms = set_flag(perms, WRITE)
    println("set WRITE   -> {perms:03b}")

    val has_read:    bool = is_flag_set(perms, READ)
    val has_execute: bool = is_flag_set(perms, EXECUTE)
    println("has READ    -> {has_read}")
    println("has EXECUTE -> {has_execute}")

    perms = toggle_flag(perms, WRITE)
    println("xor WRITE   -> {perms:03b}")

    val full_mask: i32 = READ | WRITE | EXECUTE   // 0b111 = 7
    val active: i32 = perms & full_mask
    println("masked      -> {active:03b} = {active}")

    return active
}