The Manifest

The manifest is a description of your plugin and some of the runtime constraints to apply to it. You can think of it as a blueprint to build your plugin.

wasm = open("../wasm/code.wasm", 'rb').read()
wasm_hash = hashlib.sha256(wasm).hexdigest()
manifest = {
    "wasm": [
        {
            "data": wasm,
            "hash": wasm_hash
        }
    ],
    "memory": {
        "max_pages": 5
    }
}

plugin = context.plugin(manifest)

Schema

schema.py

{
    # The "wasm" key describes the wasm code needed to build the plugin.
    # There are a few ways to load wasm code:
    "wasm": [
        # you can point to a file:
        {
            # a file path for a plugin on disk
            "path": "./code/myplugin.wasm",
            # an optional name
            "name": "main",
            # the optional sha256 hash in hex form (it's optional, but recommended)
            "hash": "15c66d72f683e0225c774134b42ba6e04275a7a56b0a522af538d029650f15a8",
        },
        # or, you can pass raw binary data for the code already in memory:
        {
            # the base64-encoded raw bytes of the wasm module
            "data": open("../wasm/code.wasm", 'rb').read(),
            # an optional name
            "name": "main",
            # the optional sha256 hash in hex form (it's optional, but recommended)
            "hash": "15c66d72f683e0225c774134b42ba6e04275a7a56b0a522af538d029650f15a8",
        },
        # or, you can load a remote resource with a URL:
        {
            # a URL to some wasm code
            "url": "https://example.com/mycode.wasm",
            # optional headers you may need to get the data, e.g. auth headers
            "headers": {
                "X-API-KEY": "34b42ba6e04275",
                "User-Agent": "extism",
            },
            # optional HTTP method to use, (default: GET)
            "method": "GET",
            # an optional name
            "name": "main",
            # the optional sha256 hash in hex form (it's optional, but recommended)
            "hash": "15c66d72f683e0225c774134b42ba6e04275a7a56b0a522af538d029650f15a8",
        },
    ]

    # Describes the limits on the memory the plugin may be allocated.
    "memory": {
        # The max amount of pages the plugin can allocate
        # One page is 64Kib. e.g. 16 pages would require 1MiB.
        "max_pages": 4,

        # The max size of an Extism HTTP response in bytes
        "max_http_response_bytes": 4096,

        # The max size of all Extism vars in bytes
        "max_var_bytes": 4096
    },

    # An optional set of hosts this plugin can communicate with.
    # This only has an effect if the plugin makes HTTP requests.
    # Note: if left empty then no hosts are allowed and if `null` then all hosts are allowed.
    "allowed_hosts": [
        "example.com",
        "extism.org",
    ],

    # An optional set of mappings between the host's filesystem and the paths a plugin can access.
    # This only has an effect if the plugin is provided with WASI capabilities. 
    # Note: if left empty or `null`, then no file access is granted.
    "allowed_paths": {
        "/path/on/disk": "plugin/path",
        "another/path": "/",
    },

    # The "config" key is a free-form map that can be passed to the plugin.
    # A plugin author must know the arbitrary data this map may contain, so your own documentation should include some information about the "config" passed in.
    "config": {
        "mykey": "myvalue"
    }
}

Validating the Manifest

If needed, we maintain an exported JSON schema for the manifest which you can find here.