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[#126] extend-freeze: include id collision odds in docstring

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Peter Taoussanis 2020-07-25 12:54:50 +02:00
parent cf84a441f4
commit 040da54936
1 changed files with 7 additions and 4 deletions
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11
src/taoensso/nippy.clj
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@ -1622,8 +1622,8 @@
(and (integer? custom-type-id) (<= 1 custom-type-id 128))))) (and (integer? custom-type-id) (<= 1 custom-type-id 128)))))
(defn- coerce-custom-type-id (defn- coerce-custom-type-id
"* +ive byte id -> -ive byte id (for unprefixed custom types) "* +ive byte id -> -ive byte id (for unprefixed custom types)
* Keyword id -> Short hash id (for prefixed custom types)" * Keyword id -> Short hash id (for prefixed custom types)"
[custom-type-id] [custom-type-id]
(assert-custom-type-id custom-type-id) (assert-custom-type-id custom-type-id)
(if-not (keyword? custom-type-id) (if-not (keyword? custom-type-id)
@ -1635,6 +1635,7 @@
;; Make sure hash ids can't collide with byte ids (unlikely anyway): ;; Make sure hash ids can't collide with byte ids (unlikely anyway):
(assert (not (<= -128 short-hash-id -1)) (assert (not (<= -128 short-hash-id -1))
"Custom type id hash collision; please choose a different id") "Custom type id hash collision; please choose a different id")
(int short-hash-id)))) (int short-hash-id))))
(comment (coerce-custom-type-id 77) (comment (coerce-custom-type-id 77)
@ -1643,8 +1644,9 @@
(defmacro extend-freeze (defmacro extend-freeze
"Extends Nippy to support freezing of a custom type (ideally concrete) with "Extends Nippy to support freezing of a custom type (ideally concrete) with
given id of form: given id of form:
* Keyword - 2 byte overhead, resistent to id collisions
* Integer ∈[1, 128] - no overhead, subject to id collisions * Keyword - 2 byte overhead, keywords hashed to 16 bit id
* ℕ∈[1, 128] - 0 byte overhead
NB: be careful about extending to interfaces, Ref. http://goo.gl/6gGRlU. NB: be careful about extending to interfaces, Ref. http://goo.gl/6gGRlU.
@ -1654,6 +1656,7 @@
;; or ;; or
(extend-freeze MyRec 1 [x data-output] ; Byte id (extend-freeze MyRec 1 [x data-output] ; Byte id
(.writeUTF [data-output] (:data x)))" (.writeUTF [data-output] (:data x)))"
[type custom-type-id [x out] & body] [type custom-type-id [x out] & body]
(assert-custom-type-id custom-type-id) (assert-custom-type-id custom-type-id)
(let [write-id-form (let [write-id-form