const expect = @import("std").testing.expect;
const print = @import("std").debug.print;

// Normal pointers in Zig cannot have 0 or null as a value. They follow the syntax *T, where T is the child type.
// Referencing is done with &variable, and dereferencing is done with variable.*.
fn increment(num: *u8) void {
    num.* += 1;
}

test "pointers" {
    var x: u8 = 1;
    increment(&x);
    try expect(x == 2);
}

// Trying to set a *T to the value 0 is detectable illegal behaviour.
test "naughty pointer" {
    var x: u16 = 5;
    x -= 5;
    var y: *u8 = @ptrFromInt(x);
    y = y;
}

// Test [23/126] test.naughty pointer... thread 21598 panic: cast causes pointer to be null
// ./test-c1.zig:252:18: 0x260a91 in test.naughty pointer (test)
//     var y: *u8 = @ptrFromInt(x);
//                  ^

// Zig also has const pointers, which cannot be used to modify the referenced data.
// Referencing a const variable will yield a const pointer.

test "const pointers" {
    // const x: u8 = 1;
    // var y = &x;
    // y.* += 1;
}

// error: cannot assign to constant
//     y.* += 1;
//         ^
// A *T coerces to a *const T.

// Pointer Sized Integers
// `usize` and `isize` are given as unsigned and signed integers which are the same size as pointers.

test "usize" {
    try expect(@sizeOf(usize) == @sizeOf(*u8));
    try expect(@sizeOf(isize) == @sizeOf(*u8));
}