Systems, system resource requests, simple runner

src/graph.zig

@@ -1,64 +1,196 @@
 const std = @import("std");
 
 // TODO:
-// - Fix alignment
+// - Use arena allocator?
+// - Resolve missing resource problem
+// - Split up this file
+
+const MAX_SYSTEM_REQUESTS = 8;
+const DEFAULT_SYSTEM_CAPACITY = 16;
 
 const HashType = u32;
 pub const HashAlgorithm = std.crypto.hash.blake2.Blake2s(32);
 
-const ResourceMap = std.AutoArrayHashMapUnmanaged(u32, *anyopaque);
+const Resource = struct {
+    /// Aligned pointer
+    pointer: *anyopaque,
+    /// Storage
+    mem: []u8,
+};
+const ResourceMap = std.AutoArrayHashMapUnmanaged(u32, Resource);
+
+const System = struct {
+    const Request = union(enum) {
+        resource: HashType,
+        // TODO:
+        // - Params
+        // - Controller
+    };
+    const RequestList = []const Request;
+
+    function_runner: *const fn ([]const *anyopaque) void,
+    requested_types: RequestList,
+
+    fn from_function(comptime function: anytype, alloc: std.mem.Allocator) !System {
+        validate_system(function);
+
+        var requests: [@typeInfo(@TypeOf(function)).Fn.params.len]Request = undefined;
+        inline for (0.., @typeInfo(@TypeOf(function)).Fn.params) |i, param| {
+            switch (@typeInfo(param.type.?).Pointer.child) {
+                else => |resource_type| requests[i] = .{ .resource = hash_type(resource_type) },
+            }
+        }
+
+        return System{
+            .requested_types = try alloc.dupe(Request, &requests),
+            .function_runner = generate_runner(function),
+        };
+    }
+    fn deinit(self: System, alloc: std.mem.Allocator) void {
+        alloc.free(self.requested_types);
+    }
+};
+const SystemQueue = std.ArrayListUnmanaged(System);
 
 alloc: std.mem.Allocator,
 resources: ResourceMap,
+system_queue: SystemQueue,
 
 const Self = @This();
 pub fn init(alloc: std.mem.Allocator) !Self {
-    const resources = try ResourceMap.init(alloc);
+    var resources = try ResourceMap.init(alloc, &.{}, &.{});
     errdefer resources.deinit(alloc);
 
+    var system_queue = try SystemQueue.initCapacity(alloc, DEFAULT_SYSTEM_CAPACITY);
+    errdefer system_queue.deinit(alloc);
+
     return .{
         .alloc = alloc,
         .resources = resources,
+        .system_queue = system_queue,
     };
 }
 
 pub fn deinit(self: *Self) void {
     var resource_iter = self.resources.iterator();
     while (resource_iter.next()) |entry| {
-        self.alloc.free(entry.value_ptr.*);
+        self.alloc.free(entry.value_ptr.mem);
     }
     self.resources.clearAndFree(self.alloc);
     self.resources.deinit(self.alloc);
+
+    for (self.system_queue.items) |system| {
+        self.alloc.free(system.requested_types);
+    }
+    self.system_queue.deinit(self.alloc);
+}
+
+fn enqueue_system(self: *Self, comptime function: anytype) !void {
+    validate_system(function);
+    const system = try System.from_function(function, self.alloc);
+    errdefer system.deinit(self.alloc);
+
+    try self.system_queue.append(self.alloc, system);
+}
+
+fn run_all_systems(self: *Self) GraphError!void {
+    while (self.system_queue.items.len > 0) {
+        const next_system = self.system_queue.getLast();
+        defer next_system.deinit(self.alloc);
+        defer _ = self.system_queue.pop();
+
+        try self.run_system(next_system);
+    }
+}
+
+/// Does not consume the system
+fn run_system(self: *Self, system: System) GraphError!void {
+    var buffer: [MAX_SYSTEM_REQUESTS]*anyopaque = undefined;
+    var buffer_len: usize = 0;
+    for (system.requested_types) |request| {
+        switch (request) {
+            .resource => |resource| {
+                buffer[buffer_len] = self.get_anyopaque_resource(resource) orelse return GraphError.MissingResource;
+            },
+        }
+        buffer_len += 1;
+    }
+    system.function_runner(buffer[0..buffer_len]);
+}
+
+pub inline fn get_resource(self: *Self, comptime resource: type) ?*resource {
+    validate_resource(resource);
+    if (get_anyopaque_resource(self, hash_type(resource))) |ptr| {
+        return @alignCast(@ptrCast(ptr));
+    }
+    return null;
+}
+
+fn get_anyopaque_resource(self: *Self, resource_hash: HashType) ?*anyopaque {
+    if (self.resources.get(resource_hash)) |resource| {
+        return resource.pointer;
+    }
+    return null;
 }
 
 /// Copies resource into storage, returning previous value if any
 pub inline fn add_resource(self: *Self, resource: anytype) !?@TypeOf(resource) {
-    // Inlined to not create millions of functions
+    validate_resource(@TypeOf(resource));
     var previous: @TypeOf(resource) = undefined;
-    if (try self.add_anyopaque_resource(&resource, hash_type(@TypeOf(resource)), @sizeOf(resource), &previous)) {
+    if (try self.add_anyopaque_resource(
+        @ptrCast(&resource),
+        hash_type(@TypeOf(resource)),
+        @sizeOf(@TypeOf(resource)),
+        @alignOf(@TypeOf(resource)),
+        @ptrCast(&previous),
+    )) {
         return previous;
     }
+    return null;
 }
 
-pub fn add_anyopaque_resource(self: *Self, resource: *const anyopaque, hash: HashType, size: usize, previous_output: *anyopaque) !bool {
+/// `previous_output` is expected to be aligned accordingly
-    const resource_buffer = try self.alloc.alloc(u8, size);
+fn add_anyopaque_resource(
-    std.mem.copyForwards(u8, resource_buffer, resource);
+    self: *Self,
-    const previous = try self.resources.fetchPut(self.alloc, hash, resource_buffer);
+    resource: *const anyopaque,
-    if (previous != null) |previous_value| {
+    hash: HashType,
-        std.mem.copyForwards(u8, previous_output, &previous_value.value);
+    size: usize,
+    align_to: usize,
+    previous_output: *anyopaque,
+) !bool {
+    // TODO: Review this shady function
+    const resource_buffer = try self.alloc.alloc(u8, size + align_to);
+    errdefer self.alloc.free(resource_buffer);
+
+    const align_offset = std.mem.alignPointerOffset(
+        @as([*]u8, @ptrCast(resource_buffer)),
+        align_to,
+    ) orelse unreachable;
+
+    @memcpy(
+        resource_buffer[align_offset..size],
+        @as([*]const u8, @ptrCast(resource))[0..size],
+    );
+    const previous = try self.resources.fetchPut(self.alloc, hash, .{
+        .pointer = @ptrCast(resource_buffer[align_offset..]),
+        .mem = resource_buffer,
+    });
+    if (previous) |previous_value| {
+        @memcpy(
+            @as([*]u8, @ptrCast(previous_output)),
+            @as([*]const u8, @ptrCast(&previous_value.value.pointer))[0..size],
+        );
+        self.alloc.free(previous_value.value.mem);
         return true;
     }
     return false;
 }
 
-fn hash_type(comptime h_type: type) HashType {
+inline fn hash_type(comptime h_type: type) HashType {
-    comptime {
     return hash_string(@typeName(h_type));
-    }
 }
 
 fn hash_string(comptime name: []const u8) HashType {
-    comptime {
     @setEvalBranchQuota(100000);
     var output: [@divExact(@bitSizeOf(HashType), 8)]u8 = undefined;
 
@@ -68,5 +200,71 @@ fn hash_string(comptime name: []const u8) HashType {
         output[0..],
         @import("builtin").cpu.arch.endian(),
     );
+}
+
+fn validate_resource(comptime resource_type: type) void {
+    switch (@typeInfo(resource_type)) {
+        .Struct, .Enum, .Union => return,
+        else => @compileError("Invalid resource type \"" ++ @typeName(resource_type) ++ "\""),
     }
 }
+
+fn validate_system(comptime system: anytype) void {
+    const info = @typeInfo(@TypeOf(system));
+    if (info != .Fn) @compileError("System can only be a function, got " ++ @typeName(system));
+    if (info.Fn.return_type != void) @compileError("Systems are not allowed to return any value (" ++ @typeName(info.Fn.return_type.?) ++ " returned)");
+    if (info.Fn.is_var_args) @compileError("System cannot be variadic");
+    if (info.Fn.is_generic) @compileError("System cannot be generic");
+    inline for (info.Fn.params) |param| {
+        if (@typeInfo(param.type.?) != .Pointer) @compileError("Systems can only have pointer parameters");
+        validate_resource(@typeInfo(param.type.?).Pointer.child);
+    }
+}
+
+fn generate_runner(comptime system: anytype) fn ([]const *anyopaque) void {
+    const RunnerImpl = struct {
+        fn runner(resources: []const *anyopaque) void {
+            var args: std.meta.ArgsTuple(@TypeOf(system)) = undefined;
+            inline for (0..@typeInfo(@TypeOf(system)).Fn.params.len) |index| {
+                args[index] = @alignCast(@ptrCast(resources[index]));
+            }
+            @call(.always_inline, system, args);
+        }
+    };
+    return RunnerImpl.runner;
+}
+
+const GraphError = error{
+    MissingResource,
+};
+
+test {
+    const Graph = @This();
+    const TestResource = struct {
+        number: u32,
+
+        fn add_one(rsc: *@This()) void {
+            rsc.number += 1;
+        }
+        fn add_ten(rsc: *@This()) void {
+            rsc.number += 10;
+        }
+    };
+
+    var graph = try Graph.init(std.testing.allocator);
+    defer graph.deinit();
+
+    try std.testing.expectEqual(graph.add_resource(TestResource{ .number = 100 }), null);
+
+    try graph.enqueue_system(TestResource.add_one);
+    try graph.enqueue_system(TestResource.add_one);
+    try graph.enqueue_system(TestResource.add_one);
+
+    try graph.enqueue_system(TestResource.add_ten);
+    try graph.enqueue_system(TestResource.add_ten);
+
+    try graph.run_all_systems();
+
+    const result = graph.get_resource(TestResource);
+    try std.testing.expectEqual(result.?.number, 123);
+}