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package types
// Handler defines the core of the state transition function of an application.
type Handler func(ctx Context, msg Msg) Result
// AnteHandler authenticates transactions, before their internal messages are handled.
// If newCtx.IsZero(), ctx is used instead.
type AnteHandler func(ctx Context, tx Tx, simulate bool) (newCtx Context, err error)
// AnteDecorator wraps the next AnteHandler to perform custom pre- and post-processing.
type AnteDecorator interface {
AnteHandle(ctx Context, tx Tx, simulate bool, next AnteHandler) (newCtx Context, err error)
}
// ChainDecorator chains AnteDecorators together with each AnteDecorator
// wrapping over the decorators further along chain and returns a single AnteHandler.
//
// NOTE: The first element is outermost decorator, while the last element is innermost
// decorator. Decorator ordering is critical since some decorators will expect
// certain checks and updates to be performed (e.g. the Context) before the decorator
// is run. These expectations should be documented clearly in a CONTRACT docline
// in the decorator's godoc.
//
// NOTE: Any application that uses GasMeter to limit transaction processing cost
// MUST set GasMeter with the FIRST AnteDecorator. Failing to do so will cause
// transactions to be processed with an infinite gasmeter and open a DOS attack vector.
// Use `ante.SetUpContextDecorator` or a custom Decorator with similar functionality.
func ChainAnteDecorators(chain ...AnteDecorator) AnteHandler {
if (chain[len(chain)-1] != Terminator{}) {
chain = append(chain, Terminator{})
}
if len(chain) == 1 {
return func(ctx Context, tx Tx, simulate bool) (Context, error) {
return chain[0].AnteHandle(ctx, tx, simulate, nil)
}
}
return func(ctx Context, tx Tx, simulate bool) (Context, error) {
return chain[0].AnteHandle(ctx, tx, simulate, ChainAnteDecorators(chain[1:]...))
}
}
// Terminator AnteDecorator will get added to the chain to simplify decorator code
// Don't need to check if next == nil further up the chain
// ______
// <((((((\\\
// / . }\
// ;--..--._|}
// (\ '--/\--' )
// \\ | '-' :'|
// \\ . -==- .-|
// \\ \.__.' \--._
// [\\ __.--| // _/'--.
// \ \\ .'-._ ('-----'/ __/ \
// \ \\ / __>| | '--. |
// \ \\ | \ | / / /
// \ '\ / \ | | _/ /
// \ \ \ | | / /
// snd \ \ \ /
type Terminator struct{}
// Simply return provided Context and nil error
func (t Terminator) AnteHandle(ctx Context, _ Tx, _ bool, _ AnteHandler) (Context, error) {
return ctx, nil
}
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