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Update readme example with manual serdes for style

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Joshua Suskalo 2022-01-19 10:57:01 -06:00
parent 7ec2cd1575
commit 5ae32161b3
1 changed files with 23 additions and 21 deletions
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README.md
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@ -593,27 +593,29 @@ As an example, when wrapping a function that returns an array of big-endian
floats, the following code might be used. floats, the following code might be used.
``` clojure ``` clojure
(let [function-handle (ffi/make-downcall "returns_float_array" [::mem/pointer] ::mem/int) (def ^:private returns-float-array* (ffi/make-downcall "returns_float_array" [::mem/pointer] ::mem/int))
release-floats (ffi/make-downcall "releases_float_array" [::mem/pointer] ::mem/void) (def ^:private release-floats* (ffi/make-downcall "releases_float_array" [::mem/pointer] ::mem/void))
pointer-size (mem/size-of ::mem/pointer)
float-size (mem/size-of ::mem/float)] (defn returns-float-array
(defn returns-float-array
[] []
(with-open [scope (mem/stack-scope)] (with-open [scope (mem/stack-scope)]
(let [out-floats (mem/alloc pointer-size scope) (let [out-floats (mem/alloc mem/pointer-size scope)
num-floats (function-handle (mem/address-of out-floats)) num-floats (function-handle (mem/address-of out-floats))
floats-addr (mem/read-address out-floats) floats-addr (mem/read-address out-floats)
floats-slice (mem/slice-global floats-addr (unchecked-multiply-int float-size num-floats)) floats-slice (mem/slice-global floats-addr (unchecked-multiply-int mem/float-size num-floats))]
ret (loop [floats (transient []) ;; Using a try/finally to perform an operation when the stack frame exits,
;; but not to try to catch anything.
(try
(loop [floats (transient [])
index 0] index 0]
(if (>= index num-floats) (if (>= index num-floats)
(persistent! floats) (persistent! floats)
(recur (conj! floats (mem/read-float floats-slice (recur (conj! floats (mem/read-float floats-slice
(unchecked-multiply-int index float-size) (unchecked-multiply-int index mem/float-size)
mem/big-endian)) mem/big-endian))
(unchecked-inc-int index))))] (unchecked-inc-int index))))
(release-floats floats-addr) (finally
ret)))) (release-floats floats-addr))))))
``` ```
The above code manually performs all memory operations rather than relying on The above code manually performs all memory operations rather than relying on