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improvements for async-io

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This commit is contained in:
Chris Boesch
2026-04-06 16:57:48 +02:00
parent 446da3ce5a
commit 63e506586f
2 changed files with 13 additions and 7 deletions
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12
exercises/089_async5.zig
View File

@@ -5,7 +5,7 @@
// Every Future has a .cancel() method that: // Every Future has a .cancel() method that:
// 1. Requests the task to stop (via error.Canceled at the // 1. Requests the task to stop (via error.Canceled at the
// next "cancellation point") // next "cancellation point")
// 2. Waits for the task to actually finish // 2. BLOCKS until the task actually finishes
// 3. Returns whatever result the task produced // 3. Returns whatever result the task produced
// //
// A "cancellation point" is any Io function that can return // A "cancellation point" is any Io function that can return
@@ -13,7 +13,7 @@
// //
// fn myTask(io: std.Io) u32 { // fn myTask(io: std.Io) u32 {
// io.sleep(...) catch |err| switch (err) { // io.sleep(...) catch |err| switch (err) {
// error.Canceled => return 0, // handle gracefully // error.Canceled => return 0, // error handle
// }; // };
// return 42; // return 42;
// } // }
@@ -21,6 +21,11 @@
// This is fundamentally different from killing a thread - // This is fundamentally different from killing a thread -
// the task gets a chance to clean up and return a value! // the task gets a chance to clean up and return a value!
// //
// Remember: both .await() and .cancel() block and return the
// result. The only difference is that .cancel() also sends
// the cancellation request. And both are idempotent — calling
// either one again just returns the same result.
//
// Fix this program: the slow task would take 10 seconds, // Fix this program: the slow task would take 10 seconds,
// but we cancel it after 1 second. The task should detect // but we cancel it after 1 second. The task should detect
// the cancellation and return early. // the cancellation and return early.
@@ -32,6 +37,7 @@ pub fn main(init: std.process.Init) !void {
const io = init.io; const io = init.io;
var future = io.async(slowTask, .{io}); var future = io.async(slowTask, .{io});
defer _ = future.cancel(io); // safety net
// Wait 1 second, then cancel instead of waiting the full 10. // Wait 1 second, then cancel instead of waiting the full 10.
io.sleep(std.Io.Duration.fromSeconds(1), .awake) catch {}; io.sleep(std.Io.Duration.fromSeconds(1), .awake) catch {};
@@ -40,7 +46,7 @@ pub fn main(init: std.process.Init) !void {
// We don't want to wait 10 seconds! // We don't want to wait 10 seconds!
// Which Future method requests cancellation AND returns the result? // Which Future method requests cancellation AND returns the result?
const result = ???; const result = future.???(io);
print("Task returned: {}\n", .{result}); print("Task returned: {}\n", .{result});
} }

8
patches/patches/089_async5.patch
View File

@@ -1,10 +1,10 @@
--- exercises/089_async5.zig 2026-04-01 23:40:40.505855238 +0200 --- exercises/089_async5.zig 2026-04-06 14:38:54.443726849 +0200
+++ answers/089_async5.zig 2026-04-01 23:40:10.176236971 +0200 +++ answers/089_async5.zig 2026-04-06 14:38:39.945438309 +0200
@@ -40,7 +40,7 @@ @@ -46,7 +46,7 @@
// We don't want to wait 10 seconds! // We don't want to wait 10 seconds!
// Which Future method requests cancellation AND returns the result? // Which Future method requests cancellation AND returns the result?
- const result = ???; - const result = future.???(io);
+ const result = future.cancel(io); + const result = future.cancel(io);
print("Task returned: {}\n", .{result}); print("Task returned: {}\n", .{result});