Add --js-library support (#16)

* Add `--js-library` support

* Dedupe code

Author: hazeycode

build.zig

@@ -151,7 +151,6 @@ pub const EmsdkAllocator = enum {
 pub const EmccDefaultSettingsOverrides = struct {
     optimize: std.builtin.OptimizeMode,
     emsdk_allocator: EmsdkAllocator = .emmalloc,
-    shell_file: ?[]const u8 = null,
 };
 
 pub fn emccDefaultSettings(allocator: std.mem.Allocator, options: EmccDefaultSettingsOverrides) EmccSettings {
@@ -182,6 +181,7 @@ pub const StepOptions = struct {
     embed_paths: ?[]const EmccFilePath = null,
     preload_paths: ?[]const EmccFilePath = null,
     shell_file_path: ?std.Build.LazyPath = null,
+    js_library_path: ?std.Build.LazyPath = null,
     out_file_name: ?[]const u8 = null,
     install_dir: std.Build.InstallDir,
 };
@@ -227,13 +227,9 @@ pub fn emccStep(
     }
 
     emcc.addArg("-o");
-    const out_file = out_file: {
-        if (options.out_file_name) |out_file_name| {
-            break :out_file emcc.addOutputFileArg(out_file_name);
-        } else {
-            break :out_file emcc.addOutputFileArg(b.fmt("{s}.html", .{wasm.name}));
-        }
-    };
+    const out_file = emcc.addOutputFileArg(
+        options.out_file_name orelse b.fmt("{s}.html", .{wasm.name}),
+    );
 
     if (options.use_preload_plugins) {
         emcc.addArg("--use-preload-plugins");
@@ -273,6 +269,12 @@ pub fn emccStep(
         emcc.addFileInput(shell_file_path);
     }
 
+    if (options.js_library_path) |js_library_path| {
+        emcc.addArg("--js-library");
+        emcc.addFileArg(js_library_path);
+        emcc.addFileInput(js_library_path);
+    }
+
     const install_step = b.addInstallDirectory(.{
         .source_dir = out_file.dirname(),
         .install_dir = options.install_dir,

src/zemscripten.zig

@@ -11,7 +11,7 @@ pub extern fn emscripten_sleep(ms: u32) void;
 pub const MainLoopCallback = *const fn () callconv(.c) void;
 extern fn emscripten_set_main_loop(MainLoopCallback, c_int, c_int) void;
 pub fn setMainLoop(cb: MainLoopCallback, maybe_fps: ?i16, simulate_infinite_loop: bool) void {
-    emscripten_set_main_loop(cb, if (maybe_fps) |fps| fps else -1, @intFromBool(simulate_infinite_loop));
+    emscripten_set_main_loop(cb, maybe_fps orelse -1, @intFromBool(simulate_infinite_loop));
 }
 
 extern fn emscripten_cancel_main_loop() void;
@@ -22,7 +22,7 @@ pub fn cancelMainLoop() void {
 pub const MainLoopArgCallback = *const fn (arg: *anyopaque) callconv(.c) void;
 extern fn emscripten_set_main_loop_arg(MainLoopArgCallback, arg: *anyopaque, c_int, c_int) void;
 pub fn setMainLoopArg(cb: MainLoopArgCallback, arg: *anyopaque, maybe_fps: ?i16, simulate_infinite_loop: bool) void {
-    emscripten_set_main_loop_arg(cb, arg, if (maybe_fps) |fps| fps else -1, @intFromBool(simulate_infinite_loop));
+    emscripten_set_main_loop_arg(cb, arg, maybe_fps orelse -1, @intFromBool(simulate_infinite_loop));
 }
 
 pub const AnimationFrameCallback = *const fn (f64, ?*anyopaque) callconv(.c) c_int;
@@ -111,9 +111,8 @@ pub const EmmallocAllocator = struct {
     ) ?[*]u8 {
         _ = ctx;
         _ = return_address;
-        const ptr_align: u32 = @as(u32, 1) << @as(u5, @intFromEnum(ptr_align_log2));
-        if (!std.math.isPowerOfTwo(ptr_align)) unreachable;
-        const ptr = emmalloc_memalign(ptr_align, len) orelse return null;
+        const ptr_align = ptr_align_log2.toByteUnits();
+        const ptr = emmalloc_memalign(@intCast(ptr_align), @intCast(len)) orelse return null;
         return @ptrCast(ptr);
     }
 
@@ -127,7 +126,7 @@ pub const EmmallocAllocator = struct {
         _ = ctx;
         _ = return_address;
         _ = buf_align_log2;
-        return emmalloc_realloc_try(buf.ptr, new_len) != null;
+        return emmalloc_realloc_try(buf.ptr, @intCast(new_len)) != null;
     }
 
     fn remap(