update the init templates to new std API

lib/init/src/main.zig

@@ -1,10 +1,32 @@
 const std = @import("std");
+const Io = std.Io;
+
 const _NAME = @import(".NAME");
 
 pub fn main() !void {
-    // Prints to stderr, ignoring potential errors.
+    // Prints to stderr, unbuffered, ignoring potential errors.
     std.debug.print("All your {s} are belong to us.\n", .{"codebase"});
-    try _NAME.bufferedPrint();
+
+    // In order to allocate memory we must construct an `Allocator` instance.
+    var debug_allocator: std.heap.DebugAllocator(.{}) = .init;
+    defer _ = debug_allocator.deinit(); // This checks for leaks.
+    const gpa = debug_allocator.allocator();
+
+    // In order to do I/O operations we must construct an `Io` instance.
+    var threaded: std.Io.Threaded = .init(gpa);
+    defer threaded.deinit();
+    const io = threaded.io();
+
+    // Stdout is for the actual output of your application, for example if you
+    // are implementing gzip, then only the compressed bytes should be sent to
+    // stdout, not any debugging messages.
+    var stdout_buffer: [1024]u8 = undefined;
+    var stdout_file_writer: Io.File.Writer = .init(.stdout(), io, &stdout_buffer);
+    const stdout_writer = &stdout_file_writer.interface;
+
+    try _NAME.printAnotherMessage(stdout_writer);
+
+    try stdout_writer.flush(); // Don't forget to flush!
 }
 
 test "simple test" {

lib/init/src/root.zig

@@ -1,17 +1,12 @@
-//! By convention, root.zig is the root source file when making a library.
+//! By convention, root.zig is the root source file when making a package.
 const std = @import("std");
+const Io = std.Io;
 
-pub fn bufferedPrint() !void {
-    // Stdout is for the actual output of your application, for example if you
-    // are implementing gzip, then only the compressed bytes should be sent to
-    // stdout, not any debugging messages.
-    var stdout_buffer: [1024]u8 = undefined;
-    var stdout_writer = std.fs.File.stdout().writer(&stdout_buffer);
-    const stdout = &stdout_writer.interface;
-
-    try stdout.print("Run `zig build test` to run the tests.\n", .{});
-
-    try stdout.flush(); // Don't forget to flush!
+/// This is a documentation comment to explain the `printAnotherMessage` function below.
+///
+/// Accepting an `Io.Writer` instance is a handy way to write reusable code.
+pub fn printAnotherMessage(writer: *Io.Writer) Io.Writer.Error!void {
+    try writer.print("Run `zig build test` to run the tests.\n", .{});
 }
 
 pub fn add(a: i32, b: i32) i32 {