Library
Module
Module type
Parameter
Class
Class type
Extism bindings for OCaml
Extism is a framework for executing WebAssembly plugins. The OCaml bindings require libextism, installation information is available on the Extism website
Plugin
and Manifest
modules are the main modules to look at.Type
provides different types that can be encoded as input/output to Plugin.call
Function
is used to define host functions and Host_function
is used from inside host functions to access the plugin memoryThe following loads a Plugin
from a file on disk using Manifest
then calls a function with a string and prints the string output:
open Extism
let () =
let plugin =
Plugin.of_manifest_exn
@@ Manifest.create [ Manifest.Wasm.file "test/code.wasm" ]
in
let res =
Plugin.call_string_exn plugin ~name:"count_vowels" "input data"
in
print_endline res
Using the typed plugin interface you can pre-define plug-in functions:
open Extism
module Example = struct
include Plugin.Typed.Init ()
let count_vowels = exn @@ fn "count_vowels" Type.string Type.string
end
let () =
let plugin =
Example.of_plugin_exn
@@ Plugin.of_manifest_exn
@@ Manifest.create [ Manifest.Wasm.file "test/code.wasm" ]
in
let res =
Example.count_vowels plugin "input data"
in
print_endline res
module Manifest = Extism_manifest
The Manifest
module is a reference to the Extism_manifest
package, it allows you to programatically construct Extism manifests.
module Val_type : sig ... end
Val_type
enumerates the available Wasm types, this should only be used when implementing host functions
module Val : sig ... end
Val
represents low-level WebAssembly values
module Type : sig ... end
Type
defines conversions from OCaml values in and out of Extism memory
module Host_function : sig ... end
Host_function
represents the plugin that is currently running from inside a host function definition
module Function : sig ... end
Function
is used to create new a new function, which can be called from a WebAssembly plugin
module Plugin : sig ... end
Plugins
contain functions that can be called
val set_log_file :
?level:[ `Error | `Warn | `Info | `Debug | `Trace | `Filter of string ] ->
string ->
bool
Set the log file and level for all Extism plugins, the names stdout
or stderr
can be used to write to the terminal
val set_log_custom :
?level:[ `Error | `Warn | `Info | `Debug | `Trace | `Filter of string ] ->
(string -> unit) ->
drain_logs
Set the log level and enable buffered logging. Returns a function that can be used to drain the logs
module Error : sig ... end
Extism error type
with_plugin f plugin
uses Fun.protect
to ensure that a plugin is freed when f
finished executing