Components

src/components.zig

@@ -0,0 +1,89 @@
+const std = @import("std");
+const err = @import("error.zig");
+const Game = @import("game.zig");
+
+pub const StorageOptions = struct {
+    min_capacity: usize = 32,
+};
+
+pub fn Storage(comptime T: type, comptime options: StorageOptions) type {
+    return struct {
+        pub const Key = packed struct {
+            cell: u32,
+            version: u32,
+        };
+        pub const MIN_CAPACITY = options.min_capacity;
+
+        const Array = std.ArrayListUnmanaged;
+        const Cell = struct {
+            component: T,
+            version: u32,
+            count: u32,
+        };
+
+        components: Array(Cell),
+
+        const Self = @This();
+        pub fn init() Self {
+            return .{
+                .components = Array(Cell).empty,
+            };
+        }
+        pub fn deinit(self: *Self) void {
+            self.components.deinit(Game.alloc);
+        }
+        pub fn add(self: *Self, component: T) Key {
+            for (0.., self.components.items) |i, *cell| {
+                if (cell.count == 0) {
+                    return populateCell(cell, i, component);
+                }
+            }
+            const cell = self.components.addOne(Game.alloc) catch err.oom();
+            return populateCell(cell, self.components.items.len - 1, component);
+        }
+        pub fn lock(self: *Self, key: Key) void {
+            self.components.items[key.cell].count += 1;
+        }
+        pub fn get(self: *Self, key: Key) ?*T {
+            const cell = &self.components.items[key.cell];
+            if (cell.version == key.version) {
+                return &cell.component;
+            }
+            return null;
+        }
+        pub fn free(self: *Self, key: Key) bool {
+            self.components.items[key.cell].count -= 1;
+        }
+        pub fn iter(self: *Self) Iterator {
+            return .{
+                .array = self.components.items,
+                .current = 0,
+            };
+        }
+
+        fn populateCell(cell: *Cell, index: usize, component: T) Key {
+            cell.version += 1;
+            cell.count = 1;
+            cell.component = component;
+            return .{
+                .cell = @intCast(index),
+                .version = cell.version,
+            };
+        }
+
+        pub const Iterator = struct {
+            array: []Cell,
+            current: usize,
+
+            pub fn next(self: *@This()) ?*T {
+                while (self.current < self.array.len) {
+                    defer self.current += 1;
+                    if (self.array[self.current].count != 0) {
+                        return &self.array[self.current].component;
+                    }
+                }
+                return null;
+            }
+        };
+    };
+}

src/game.zig

@@ -13,7 +13,7 @@ const Time = struct {
     now: sdl.Time,
 };
 
-var alloc: std.mem.Allocator = undefined;
+pub var alloc: std.mem.Allocator = undefined;
 
 var running: bool = false;
 var time: Time = .{ .delta = 0, .now = 0 };

src/world.zig

@@ -1,10 +1,11 @@
 const Graphics = @import("graphics.zig");
 const Entity = @import("entity.zig");
 const Time = @import("time.zig");
+const comp = @import("components.zig");
 
 pub var time: Time = undefined;
 var next_stop: Time = undefined;
-var entities: [16]?Entity = undefined;
+var entities: comp.Storage(Entity, .{}) = undefined;
 
 pub var plane_mesh: Graphics.Mesh = undefined;
 pub var cube_mesh: Graphics.Mesh = undefined;
@@ -12,25 +13,25 @@ pub var texture: Graphics.Texture = undefined;
 
 const World = @This();
 pub fn initDebug() void {
-    entities = .{null} ** 16;
-    entities[0] = .{
+    entities = comp.Storage(Entity, .{}).init();
+    _ = entities.add(.{
         .position = .{ 0, 0 },
         .player = true,
-    };
-    entities[1] = .{
+    });
+    _ = entities.add(.{
         .position = .{ 2, 0 },
         .enemy = true,
         .controller = .{
             .move_units = 0.25,
         },
-    };
-    entities[2] = .{
+    });
+    _ = entities.add(.{
         .position = .{ 3, 0 },
         .enemy = true,
         .controller = .{
             .move_units = 0.25,
         },
-    };
+    });
     time = Time.ZERO;
     World.plane_mesh = Graphics.loadMesh(@ptrCast(&PLANE_MESH_DATA));
     World.cube_mesh = Graphics.loadMesh(@ptrCast(&CUBE_MESH_DATA));
@@ -41,6 +42,7 @@ pub fn deinit() void {
     Graphics.unloadMesh(World.plane_mesh);
     Graphics.unloadMesh(World.cube_mesh);
     Graphics.unloadTexture(World.texture);
+    World.entities.deinit();
 }
 
 pub fn updateReal(delta: f32) void {
@@ -49,16 +51,18 @@ pub fn updateReal(delta: f32) void {
         const current = Time.earliest(World.next_stop, update_until);
         defer World.time = current;
 
-        for (&World.entities) |*entity| {
-            if (entity.*) |*e| e.update();
+        var iter = World.entities.iter();
+        while (iter.next()) |entity| {
+            entity.update();
         }
     }
 }
 
 pub fn draw(delta: f32) void {
     Graphics.drawMesh(World.plane_mesh, World.texture, .{ .scale = @splat(5) });
-    for (&World.entities) |*entity| {
-        if (entity.*) |*e| e.draw(delta);
+    var iter = World.entities.iter();
+    while (iter.next()) |entity| {
+        entity.draw(delta);
     }
 }
 
@@ -67,11 +71,10 @@ pub fn requestUpdate(at: Time) void {
 }
 
 pub fn entityAt(position: @Vector(2, i32)) ?*Entity {
-    for (&World.entities) |*maybe_entity| {
-        if (maybe_entity.*) |*entity| {
-            if (@reduce(.And, entity.position == position))
-                return entity;
-        }
+    var iter = World.entities.iter();
+    while (iter.next()) |entity| {
+        if (@reduce(.And, entity.position == position))
+            return entity;
     }
     return null;
 }
@@ -81,11 +84,10 @@ pub fn isFree(position: @Vector(2, i32)) bool {
 }
 
 pub fn getPlayer() ?*Entity {
-    for (&World.entities) |*maybe_entity| {
-        if (maybe_entity.*) |*entity| {
-            if (entity.player)
-                return entity;
-        }
+    var iter = World.entities.iter();
+    while (iter.next()) |entity| {
+        if (entity.player)
+            return entity;
     }
     return null;
 }