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106 lines
3.6 KiB
V
106 lines
3.6 KiB
V
// This module defines the Context type, which carries deadlines, cancellation signals,
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// and other request-scoped values across API boundaries and between processes.
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// Based on: https://github.com/golang/go/tree/master/src/context
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// Last commit: https://github.com/golang/go/commit/52bf14e0e8bdcd73f1ddfb0c4a1d0200097d3ba2
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module context
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import time
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const (
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cancel_context_key = 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 = error('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 = error('context deadline exceeded')
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)
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// Key represents the type for the ValueContext key
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pub type Key = bool | f32 | f64 | i16 | i64 | i8 | int | string | u16 | u32 | u64 | u8 | voidptr
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// Any represents a generic type for the ValueContext
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pub interface Any {}
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// `Context` is an interface that defined the minimum required functionality
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// for a Context.
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//
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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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//
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// `value(key)` returns an Optional that wraps the value associated with this context for key.
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// It returns none 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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// modules should define keys as an unexported type to avoid
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// collisions.
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//
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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 a closed channel 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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//
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// `err()` returns an IError based on some conditions
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// If done is not yet closed, err returns none.
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// If done is closed, err returns a non-none 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-none error, successive calls to err return the same error.
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pub interface Context {
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deadline() ?time.Time
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value(key Key) ?Any
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mut:
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done() chan int
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err() IError
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}
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// str returns the `str` method of the corresponding Context struct
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pub fn (ctx &Context) str() string {
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// since `Context` is an interface we have to manually match every possible
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// type that implements `Context` if we want to use a `Context` as a field in a struct
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// since the `Context` interface has to implement its own `str` method.
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match ctx {
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BackgroundContext {
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return ctx.str()
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}
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EmptyContext {
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return ctx.str()
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}
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TodoContext {
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return ctx.str()
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}
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CancelContext {
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return ctx.str()
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}
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TimerContext {
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return ctx.str()
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}
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ValueContext {
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return ctx.str()
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}
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else {
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return context_name(ctx)
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}
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}
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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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