78 lines
2.9 KiB
V
78 lines
2.9 KiB
V
module context
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import time
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pub const (
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background = EmptyContext(0)
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todo = EmptyContext(1)
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cancel_context_key = 'context.CancelContext'
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// canceled is the error returned by Context.err when the context is canceled.
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canceled = 'context canceled'
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// deadline_exceeded is the error returned by Context.err when the context's
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// deadline passes.
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deadline_exceeded = 'context deadline exceeded'
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)
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pub interface Context {
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// deadline returns the time when work done on behalf of this context
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// should be canceled. deadline returns none when no deadline is
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// set. Successive calls to deadline return the same results.
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deadline() ?time.Time
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// done returns a channel that's closed when work done on behalf of this
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// context should be canceled. done may return nil if this context can
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// never be canceled. Successive calls to done return the same value.
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// The close of the done channel may happen asynchronously,
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// after the cancel function returns.
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//
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// with_cancel arranges for done to be closed when cancel is called;
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// with_deadline arranges for done to be closed when the deadline
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// expires; with_timeout arranges for done to be closed when the timeout
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// elapses.
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done() chan int
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// If done is not yet closed, err returns nil.
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// If done is closed, err returns a non-nil error explaining why:
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// canceled if the context was canceled
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// or deadline_exceeded if the context's deadline passed.
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// After err returns a non-nil error, successive calls to err return the same error.
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err() string
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// Value returns the value associated with this context for key, or nil
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// if no value is associated with key. Successive calls to Value with
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// the same key returns the same result.
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//
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// Use context values only for request-scoped data that transits
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// processes and API boundaries, not for passing optional parameters to
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// functions.
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//
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// A key identifies a specific value in a Context. Functions that wish
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// to store values in Context typically allocate a key in a global
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// variable then use that key as the argument to context.with_value and
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// Context.Value. A key can be any type that supports equality;
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// packages should define keys as an unexported type to avoid
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// collisions.
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value(key string) ?voidptr
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str() string
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}
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// background returns an empty Context. It is never canceled, has no
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// values, and has no deadline. It is typically used by the main function,
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// initialization, and tests, and as the top-level Context for incoming
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// requests.
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pub fn background() Context {
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return context.background
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}
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// todo returns an empty Context. Code should use todo when
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// it's unclear which Context to use or it is not yet available (because the
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// surrounding function has not yet been extended to accept a Context
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// parameter).
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pub fn todo() Context {
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return context.todo
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}
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fn context_name(ctx Context) string {
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return typeof(ctx)
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}
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