Start pulling out IO thread and IO implementation

src/termio/Thread.zig

@@ -0,0 +1,140 @@
+//! Represents the IO thread logic. The IO thread is responsible for
+//! the child process and pty management.
+pub const Thread = @This();
+
+const std = @import("std");
+const builtin = @import("builtin");
+const libuv = @import("libuv");
+const termio = @import("../termio.zig");
+
+const Allocator = std.mem.Allocator;
+const log = std.log.scoped(.io_thread);
+
+/// The main event loop for the thread. The user data of this loop
+/// is always the allocator used to create the loop. This is a convenience
+/// so that users of the loop always have an allocator.
+loop: libuv.Loop,
+
+/// This can be used to wake up the thread.
+wakeup: libuv.Async,
+
+/// This can be used to stop the thread on the next loop iteration.
+stop: libuv.Async,
+
+/// The underlying IO implementation.
+impl: *termio.Impl,
+
+/// Initialize the thread. This does not START the thread. This only sets
+/// up all the internal state necessary prior to starting the thread. It
+/// is up to the caller to start the thread with the threadMain entrypoint.
+pub fn init(
+    alloc: Allocator,
+    impl: *termio.Impl,
+) !Thread {
+    // We always store allocator pointer on the loop data so that
+    // handles can use our global allocator.
+    const allocPtr = try alloc.create(Allocator);
+    errdefer alloc.destroy(allocPtr);
+    allocPtr.* = alloc;
+
+    // Create our event loop.
+    var loop = try libuv.Loop.init(alloc);
+    errdefer loop.deinit(alloc);
+    loop.setData(allocPtr);
+
+    // This async handle is used to "wake up" the renderer and force a render.
+    var wakeup_h = try libuv.Async.init(alloc, loop, wakeupCallback);
+    errdefer wakeup_h.close((struct {
+        fn callback(h: *libuv.Async) void {
+            const loop_alloc = h.loop().getData(Allocator).?.*;
+            h.deinit(loop_alloc);
+        }
+    }).callback);
+
+    // This async handle is used to stop the loop and force the thread to end.
+    var stop_h = try libuv.Async.init(alloc, loop, stopCallback);
+    errdefer stop_h.close((struct {
+        fn callback(h: *libuv.Async) void {
+            const loop_alloc = h.loop().getData(Allocator).?.*;
+            h.deinit(loop_alloc);
+        }
+    }).callback);
+
+    return Thread{
+        .loop = loop,
+        .wakeup = wakeup_h,
+        .stop = stop_h,
+        .impl = impl,
+    };
+}
+
+/// Clean up the thread. This is only safe to call once the thread
+/// completes executing; the caller must join prior to this.
+pub fn deinit(self: *Thread) void {
+    // Get a copy to our allocator
+    const alloc_ptr = self.loop.getData(Allocator).?;
+    const alloc = alloc_ptr.*;
+
+    // Schedule our handles to close
+    self.stop.close((struct {
+        fn callback(h: *libuv.Async) void {
+            const handle_alloc = h.loop().getData(Allocator).?.*;
+            h.deinit(handle_alloc);
+        }
+    }).callback);
+    self.wakeup.close((struct {
+        fn callback(h: *libuv.Async) void {
+            const handle_alloc = h.loop().getData(Allocator).?.*;
+            h.deinit(handle_alloc);
+        }
+    }).callback);
+
+    // Run the loop one more time, because destroying our other things
+    // like windows usually cancel all our event loop stuff and we need
+    // one more run through to finalize all the closes.
+    _ = self.loop.run(.default) catch |err|
+        log.err("error finalizing event loop: {}", .{err});
+
+    // Dealloc our allocator copy
+    alloc.destroy(alloc_ptr);
+
+    self.loop.deinit(alloc);
+}
+
+/// The main entrypoint for the thread.
+pub fn threadMain(self: *Thread) void {
+    // Call child function so we can use errors...
+    self.threadMain_() catch |err| {
+        // In the future, we should expose this on the thread struct.
+        log.warn("error in io thread err={}", .{err});
+    };
+}
+
+fn threadMain_(self: *Thread) !void {
+    // Run our thread start/end callbacks. This allows the implementation
+    // to hook into the event loop as needed.
+    try self.impl.threadEnter(self.loop);
+    defer self.impl.threadExit();
+
+    // Set up our async handler to support rendering
+    self.wakeup.setData(self);
+    defer self.wakeup.setData(null);
+
+    // Run
+    log.debug("starting IO thread", .{});
+    defer log.debug("exiting IO thread", .{});
+    _ = try self.loop.run(.default);
+}
+
+fn wakeupCallback(h: *libuv.Async) void {
+    _ = h;
+    // const t = h.getData(Thread) orelse {
+    //     // This shouldn't happen so we log it.
+    //     log.warn("render callback fired without data set", .{});
+    //     return;
+    // };
+}
+
+fn stopCallback(h: *libuv.Async) void {
+    h.loop().stop();
+}