ea336061c2
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The PR introduces the `platform.Select()` API, wrapping `select(2)` on POSIX and emulated in some cases on Windows. RATIONALE.md contains a full explanation of the approach followed in `poll_oneoff` to handle Stdin and the other types of file descriptors, and the clock subscriptions. It also introduces an abstraction (`StdioFilePoller`) to allow the simulation of different scenarios (waiting for input, input ready, timeout expired, etc.) when unit-testing interactive input. This closes #1317. Signed-off-by: Edoardo Vacchi <evacchi@users.noreply.github.com>
93 lines
2.1 KiB
Go
93 lines
2.1 KiB
Go
package platform
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import (
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"os"
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"runtime"
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"syscall"
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"testing"
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"time"
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"github.com/tetratelabs/wazero/internal/testing/require"
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)
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func TestSelect(t *testing.T) {
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t.Run("should return immediately with no fds and duration 0", func(t *testing.T) {
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for {
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dur := time.Duration(0)
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n, err := Select(0, nil, nil, nil, &dur)
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if err == syscall.EINTR {
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t.Logf("Select interrupted")
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continue
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}
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require.NoError(t, err)
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require.Equal(t, 0, n)
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break
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}
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})
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t.Run("should wait for the given duration", func(t *testing.T) {
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dur := 250 * time.Millisecond
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var took time.Duration
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for {
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// On some platforms (e.g. Linux), the passed-in timeval is
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// updated by select(2). We are not accounting for this
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// in our implementation.
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start := time.Now()
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n, err := Select(0, nil, nil, nil, &dur)
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took = time.Since(start)
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if err == syscall.EINTR {
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t.Logf("Select interrupted after %v", took)
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continue
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}
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require.NoError(t, err)
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require.Equal(t, 0, n)
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break
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}
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// On some platforms the actual timeout might be arbitrarily
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// less than requested.
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if took < dur {
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if runtime.GOOS == "linux" {
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// Linux promises to only return early if a file descriptor
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// becomes ready (not applicable here), or the call
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// is interrupted by a signal handler (explicitly retried in the loop above),
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// or the timeout expires.
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t.Errorf("Select: slept for %v, expected %v", took, dur)
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} else {
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t.Logf("Select: slept for %v, requested %v", took, dur)
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}
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}
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})
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t.Run("should return 1 if a given FD has data", func(t *testing.T) {
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rr, ww, err := os.Pipe()
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require.NoError(t, err)
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defer rr.Close()
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defer ww.Close()
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_, err = ww.Write([]byte("TEST"))
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require.NoError(t, err)
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rFdSet := &FdSet{}
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fd := int(rr.Fd())
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rFdSet.Set(fd)
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for {
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n, err := Select(fd+1, rFdSet, nil, nil, nil)
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if runtime.GOOS == "windows" {
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// Not implemented for fds != wasiFdStdin
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require.ErrorIs(t, err, syscall.ENOSYS)
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require.Equal(t, -1, n)
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break
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}
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if err == syscall.EINTR {
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t.Log("Select interrupted")
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continue
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}
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require.NoError(t, err)
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require.Equal(t, 1, n)
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break
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}
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})
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}
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