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The (goblins actor-lib sealers) module provides a mechanism for
ensuring the authenticity of data. A sealer is used to place data
within a wrapper. This wrapper can only be unsealed by the
corresponding unsealer, and can be checked with a predicate to ensure
it is authentic. Sealers and unsealers are analogous to public key
cryptography, but do not use any cryptography at all.
Return values holding a sealer, unsealer, and
check capability. name, if provided, is the debug name
of the underlying Scheme record object. make-sealer-triplet, if
provided, is the primitive used to create the sealer objects. Each
sealer object can be invoked with a single argument:
sealer value: Seal value and return a reference to the
sealed object.
unsealer value: Unseal the value sealed with the
corresponding sealer. If the unsealed object is near,
it is returned directly; otherwise, a promise is returned.
As an example, consider a metaphorical food delivery service and its rival service:
> (define-values (our-lunch:seal our-lunch:unseal our-can?) (spawn-sealer-triplet)) > (define-values (rival-lunch:seal rival-lunch:unseal rival-can?) (spawn-sealer-triplet)) > ($ our-lunch:seal 'fried-rice) => #<local-object sealed-value> > (define chickpea-lunch ($ our-lunch:seal 'chickpea-salad)) > ($ our-can? chickpea-lunch) => #t > ($ our-can? ($ rival-lunch:seal 'melted-ice-cream)) => #f > ($ our-lunch:unseal chickpea-lunch) => chickpea-salad
[default-make-sealer-triplet]
Returns two values, the first is a spawn-sealer-triplet
function setup with a set of custom sealers and the second is a
persistence environment for Goblins’ persistence system.
namespace is a atomic value which must uniquely identify this set of sealers within the object graph.
known-sealers is an alist mapping a unique name to a thunk which returns three values (sealer function, unsealer function and trademark function).
default-make-sealer-triplet specifies what the default make-sealer-triplet function is used when none is specified.
If a custom sealer triplet is provided to the returned
spawn-sealer-triplet function without being specified in the
known-sealers alist, an error will be thrown.
(define* (my-custom-sealer-triplet #:optional name) (define-record-type <custom-sealers> (seal val) sealed? (val unseal)) (values seal unseal sealed?)) (define custom-sealers-list `(((ward-sealer-triplet) . ,my-custom-sealer-triplet))) (define-values (custom-spawn-sealer-triplet custom-sealer-env) (make-spawn-sealer-triplet '(my-library sealers) custom-sealers-list #:default-make-sealer-triplet my-custom-sealer-triplet))
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