tulpaforce/vendor/github.com/Xe/ln/context.go

39 lines
587 B
Go
Raw Normal View History

2018-03-24 02:17:22 +00:00
package ln
import (
"context"
)
type ctxKey int
const (
fKey = iota
)
// WithF stores or appends a given F instance into a context.
func WithF(ctx context.Context, f F) context.Context {
pf, ok := FFromContext(ctx)
if !ok {
return context.WithValue(ctx, fKey, f)
}
pf.Extend(f)
return context.WithValue(ctx, fKey, pf)
}
// FFromContext fetches the `F` out of the context if it exists.
func FFromContext(ctx context.Context) (F, bool) {
fvp := ctx.Value(fKey)
if fvp == nil {
return nil, false
}
f, ok := fvp.(F)
if !ok {
return nil, false
}
return f, true
}