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>
32 lines
1.3 KiB
Go
32 lines
1.3 KiB
Go
package platform
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import "time"
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// Select exposes the select(2) syscall.
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//
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// # Notes on Parameters
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//
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// For convenience, we expose a pointer to a time.Duration instead of a pointer to a syscall.Timeval.
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// It must be a pointer because `nil` means "wait forever".
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//
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// However, notice that select(2) may mutate the pointed Timeval on some platforms,
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// for instance if the call returns early.
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//
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// This implementation *will not* update the pointed time.Duration value accordingly.
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//
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// See also: https://github.com/golang/sys/blob/master/unix/syscall_unix_test.go#L606-L617
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//
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// # Notes on the Syscall
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//
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// Because this is a blocking syscall, it will also block the carrier thread of the goroutine,
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// preventing any means to support context cancellation directly.
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//
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// There are ways to obviate this issue. We outline here one idea, that is however not currently implemented.
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// A common approach to support context cancellation is to add a signal file descriptor to the set,
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// e.g. the read-end of a pipe or an eventfd on Linux.
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// When the context is canceled, we may unblock a Select call by writing to the fd, causing it to return immediately.
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// This however requires to do a bit of housekeeping to hide the "special" FD from the end-user.
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func Select(n int, r, w, e *FdSet, timeout *time.Duration) (int, error) {
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return syscall_select(n, r, w, e, timeout)
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}
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