Inspired by wasmedge-bindgen in the Go and Rust SDKs, this module provides high-level, type-safe abstractions for invoking WebAssembly guest functions that accept and return complex data (JSON, UTF-8 strings, and raw ByteStrings) without requiring manual pointer arithmetic or allocation management.

Calling Guest Functions

import WasmEdge
import WasmEdge.Bindgen
import Data.Aeson (FromJSON, ToJSON)

data MyRequest = MyRequest { query :: Text } deriving (Generic, ToJSON)
data MyResponse = MyResponse { hits :: [Text] } deriving (Generic, FromJSON)

-- Single-line guest invocation:
response <- callGuestJson vm "search_module" "execute_search" (MyRequest "example")
case response of
  Left err  -> putStrLn $ "Error: " ++ show err
  Right res -> print (hits res)

Reading and Writing from Host Functions

When a host function is invoked by the guest, it receives a CallingFrame. This module provides helpers to read and write strings and JSON directly:

myHostLog :: CallingFrame -> [WasmVal] -> IO (WasmResult [WasmVal])
myHostLog frame [WasmI32 ptr, WasmI32 len] = do
  res <- callerReadText frame (fromIntegral ptr) (fromIntegral len)
  case res of
    Left err  -> pure (Left err)
    Right msg -> do
      putStrLn $ "Guest log: " ++ show msg
      pure (Right [])