alloc_observe.Identity

1/// Identifies an allocation source by recording a producer identifier, a2/// producer kind, an owner-supplied generation number, and an owner-supplied3/// cookie value. When observation is enabled, starting a span requires a4/// nonzero producer identifier, and specifying a nonzero generation number5/// requires a nonzero cookie. The observation layer stores and forwards these6/// values as provided by the caller without automatically tracking lifetime7/// state or advancing generation numbers.8pub const Identity = struct {9    producer_id: u64,10    producer: Producer,11    generation: u64,12    owner_cookie: usize,1314    /// Derives an identity whose cookie is computed from a nonzero producer15    /// identifier rather than a memory address. The constructor requires a16    /// nonzero producer identifier, folds the identifier into a `usize` by17    /// XORing the high word on narrower targets and truncating, and substitutes18    /// one whenever the folded result is zero. Deriving the cookie from an19    /// identifier allows owner structs to move in memory without altering their20    /// identity. This derivation does not guarantee collision-free cookie21    /// values and does not update existing allocator handles that continue to22    /// borrow old owner addresses.23    pub fn movable(24        producer_id: u64,25        producer: Producer,26        generation: u64,27    ) Identity {28        std.debug.assert(producer_id != 0);29        const folded = if (comptime @bitSizeOf(usize) < @bitSizeOf(u64))30            producer_id ^ (producer_id >> @bitSizeOf(usize))31        else32            producer_id;33        const cookie: usize = @truncate(folded);34        return .{35            .producer_id = producer_id,36            .producer = producer,37            .generation = generation,38            .owner_cookie = if (cookie == 0) 1 else cookie,39        };40    }41};

1/// Identifies an allocation source by recording a producer identifier, a2/// producer kind, an owner-supplied generation number, and an owner-supplied3/// cookie value. When observation is enabled, starting a span requires a4/// nonzero producer identifier, and specifying a nonzero generation number5/// requires a nonzero cookie. The observation layer stores and forwards these6/// values as provided by the caller without automatically tracking lifetime7/// state or advancing generation numbers.8pub const Identity = protocol.Identity;