tiny.ui.Capacity

1/// `Capacity` is the layout `Capacity.derive` computes from one `Limits`.2/// `Capacity.offsets` holds the byte offset of each table in a block, in `arrays` order.3/// `Capacity.buffer_bytes` is the size of one block, and `admit` rejects a longer publish4/// buffer with `error.PublishTooLarge`. `Capacity.total_bytes` is the size of the one5/// allocation a `Store` makes.6pub const Capacity = struct {7    limits: Limits = .{},8    offsets: [array_count]u32 = @splat(0),9    buffer_bytes: u32 = 0,10    total_bytes: u64 = 0,1112    /// `Capacity.derive` places the ten tables after the 152 byte header, each at its element13    /// alignment, and rounds the block up to 8 bytes. The total is two blocks, two identity14    /// maps of `map_slots` words, two word arrays of `nodes` entries, one of `atoms` entries,15    /// and one of `texts` entries. It returns `error.CapacityOverflow` when a size overflows16    /// or when `map_slots` is below `slotCount(nodes)`.17    pub fn derive(limits: Limits) Error!Capacity {18        var out = Capacity{ .limits = limits };19        var cursor: u32 = abi.header_bytes;20        inline for (arrays, 0..) |entry, index| {21            cursor = try alignUp(cursor, entry.alignment);22            out.offsets[index] = cursor;23            cursor = try add(cursor, try mul(@field(limits, entry.limit), entry.bytes));24        }25        out.buffer_bytes = try alignUp(cursor, block_alignment);26        if (limits.map_slots < slotCount(limits.nodes)) return error.CapacityOverflow;27        const buffers = try mul64(out.buffer_bytes, 2);28        const maps = try mul64(try mul(limits.map_slots, 4), 2);29        const dirty = try mul(limits.nodes, 4);30        const place = try mul(limits.nodes, 4);31        const atom_remap = try mul(limits.atoms, 4);32        const text_remap = try mul(limits.texts, 4);33        var total = try add64(buffers, maps);34        total = try add64(total, dirty);35        total = try add64(total, place);36        total = try add64(total, atom_remap);37        out.total_bytes = try add64(total, text_remap);38        return out;39    }40};

1pub const Capacity = tree.Capacity;