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std: Uniform polling logic for Windows and Unix

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Keep polling until there are enough open handles, if the child process
terminates closing the handles or explicitly closes them we just quit
polling and wait for the process handle to signal the termination
condition.
This commit is contained in:
LemonBoy 2020-10-21 16:54:38 +02:00 committed by Andrew Kelley
parent 2c16a96686
commit 1667c937a0
1 changed files with 21 additions and 28 deletions
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49
lib/std/child_process.zig
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@ -225,11 +225,11 @@ pub const ChildProcess = struct {
}
fn collectOutputWindows(child: *const ChildProcess, stdout: *std.ArrayList(u8), stderr: *std.ArrayList(u8), max_output_bytes: usize) !void {
// The order of the objects here is important, WaitForMultipleObjects
// uses the same order when scanning the events.
var wait_objects = [_]windows.kernel32.HANDLE{
child.handle, child.stdout.?.handle, child.stderr.?.handle,
child.stdout.?.handle, child.stderr.?.handle,
};
var waiting_objects: u32 = wait_objects.len;
// XXX: Calling zeroes([2]windows.OVERLAPPED) causes the stage1 compiler
// to crash and burn.
var overlapped = [_]windows.OVERLAPPED{
@ -241,38 +241,31 @@ pub const ChildProcess = struct {
// Kickstart the loop by issuing two async reads.
// ReadFile returns false and GetLastError returns ERROR_IO_PENDING if
// everything is ok.
_ = windows.kernel32.ReadFile(wait_objects[1], &temp_buf[0], temp_buf[0].len, null, &overlapped[0]);
_ = windows.kernel32.ReadFile(wait_objects[2], &temp_buf[1], temp_buf[1].len, null, &overlapped[1]);
_ = windows.kernel32.ReadFile(wait_objects[0], &temp_buf[0], temp_buf[0].len, null, &overlapped[0]);
_ = windows.kernel32.ReadFile(wait_objects[1], &temp_buf[1], temp_buf[1].len, null, &overlapped[1]);
while (true) {
const status = windows.kernel32.WaitForMultipleObjects(wait_objects.len, &wait_objects, 0, windows.INFINITE);
std.debug.print("status {x}\n", .{status});
poll: while (waiting_objects > 0) {
const status = windows.kernel32.WaitForMultipleObjects(waiting_objects, &wait_objects, 0, windows.INFINITE);
switch (status) {
windows.WAIT_OBJECT_0 + 0 => {
// The child process was terminated.
break;
},
windows.WAIT_OBJECT_0 + 1 => {
// stdout is ready.
windows.WAIT_OBJECT_0 + 0...windows.WAIT_OBJECT_0 + 1 => {
// stdout (or stderr) is ready.
const object = status - windows.WAIT_OBJECT_0;
var read_bytes: u32 = undefined;
if (windows.kernel32.GetOverlappedResult(wait_objects[1], &overlapped[0], &read_bytes, 0) == 0) {
if (windows.kernel32.GetOverlappedResult(wait_objects[object], &overlapped[object], &read_bytes, 0) == 0) {
switch (windows.kernel32.GetLastError()) {
.BROKEN_PIPE => {
// Move it to the end to remove it.
if (object != waiting_objects - 1)
mem.swap(windows.kernel32.HANDLE, &wait_objects[object], &wait_objects[waiting_objects - 1]);
waiting_objects -= 1;
continue :poll;
},
else => |err| return windows.unexpectedError(err),
}
}
try stdout.appendSlice(temp_buf[0][0..read_bytes]);
_ = windows.kernel32.ReadFile(wait_objects[1], &temp_buf[0], temp_buf[0].len, null, &overlapped[0]);
},
windows.WAIT_OBJECT_0 + 2 => {
// stderr is ready.
var read_bytes: u32 = undefined;
if (windows.kernel32.GetOverlappedResult(wait_objects[2], &overlapped[1], &read_bytes, 0) == 0) {
switch (windows.kernel32.GetLastError()) {
else => |err| return windows.unexpectedError(err),
}
}
try stdout.appendSlice(temp_buf[1][0..read_bytes]);
_ = windows.kernel32.ReadFile(wait_objects[2], &temp_buf[1], temp_buf[1].len, null, &overlapped[1]);
try stdout.appendSlice(temp_buf[object][0..read_bytes]);
_ = windows.kernel32.ReadFile(wait_objects[object], &temp_buf[object], temp_buf[object].len, null, &overlapped[object]);
},
windows.WAIT_FAILED => {
switch (windows.kernel32.GetLastError()) {