35 lines
551 B
Go
35 lines
551 B
Go
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package ln
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import (
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"context"
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)
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type ctxKey int
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const (
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fKey = iota
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)
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// WithF stores or appends a given F instance into a context.
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func WithF(ctx context.Context, f F) context.Context {
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pf, ok := FFromContext(ctx)
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if !ok {
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return context.WithValue(ctx, fKey, f)
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}
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pf.Extend(f)
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return context.WithValue(ctx, fKey, pf)
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}
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// FFromContext fetches the `F` out of the context if it exists.
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func FFromContext(ctx context.Context) (F, bool) {
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fvp := ctx.Value(fKey)
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if fvp == nil {
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return nil, false
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}
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f, ok := fvp.(F)
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return f, ok
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}
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