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better API for Io.async

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This commit is contained in:
Andrew Kelley 2025-03-29 15:22:00 -07:00
parent 90cc7f4adf
commit dab5dd286f
1 changed files with 9 additions and 14 deletions
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23
lib/std/Io.zig
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@ -913,7 +913,6 @@ test {
}
const Io = @This();
const fs = std.fs;
pub const EventLoop = @import("Io/EventLoop.zig");
@ -971,20 +970,16 @@ pub fn Future(Result: type) type {
};
}
/// `s` is a struct instance that contains a function like this:
/// ```
/// struct {
/// pub fn start(s: S) Result { ... }
/// }
/// ```
/// where `Result` is any type.
pub fn async(io: Io, S: type, s: S) Future(@typeInfo(@TypeOf(S.start)).@"fn".return_type.?) {
const Result = @typeInfo(@TypeOf(S.start)).@"fn".return_type.?;
/// Calls `function` with `args`, such that the return value of the function is
/// not guaranteed to be available until `await` is called.
pub fn async(io: Io, function: anytype, args: anytype) Future(@typeInfo(@TypeOf(function)).@"fn".return_type.?) {
const Result = @typeInfo(@TypeOf(function)).@"fn".return_type.?;
const Args = @TypeOf(args);
const TypeErased = struct {
fn start(context: *const anyopaque, result: *anyopaque) void {
const context_casted: *const S = @alignCast(@ptrCast(context));
const args_casted: *const Args = @alignCast(@ptrCast(context));
const result_casted: *Result = @ptrCast(@alignCast(result));
result_casted.* = S.start(context_casted.*);
result_casted.* = @call(.auto, function, args_casted.*);
}
};
var future: Future(Result) = undefined;
@ -992,8 +987,8 @@ pub fn async(io: Io, S: type, s: S) Future(@typeInfo(@TypeOf(S.start)).@"fn".ret
io.userdata,
@ptrCast((&future.result)[0..1]),
.fromByteUnits(@alignOf(Result)),
if (@sizeOf(S) == 0) &.{} else @ptrCast((&s)[0..1]), // work around compiler bug
.fromByteUnits(@alignOf(S)),
if (@sizeOf(Args) == 0) &.{} else @ptrCast((&args)[0..1]), // work around compiler bug
.fromByteUnits(@alignOf(Args)),
TypeErased.start,
);
return future;