gnu_hash

pub const gnu_hash = struct {

    // See https://flapenguin.me/elf-dt-gnu-hash

    pub const Header = extern struct {
        nbuckets: u32,
        symoffset: u32,
        bloom_size: u32,
        bloom_shift: u32,
    };

    pub const ChainEntry = packed struct(u32) {
        end_of_chain: bool,
        /// Contains the top bits of the hash value.
        hash: u31,
    };

    /// Calculate the hash value for a name
    pub fn calculate(name: []const u8) u32 {
        var h: u32 = 5381;
        for (name) |char| {
            h = (h << 5) +% h +% char;
        }
        return h;
    }

    test calculate {
        try std.testing.expectEqual(0x00001505, calculate(""));
        try std.testing.expectEqual(0x156b2bb8, calculate("printf"));
        try std.testing.expectEqual(0x7c967e3f, calculate("exit"));
        try std.testing.expectEqual(0xbac212a0, calculate("syscall"));
        try std.testing.expectEqual(0x8ae9f18e, calculate("flapenguin.me"));
    }
}