Overview

The wasmedge-sys crate defines a group of low-level Rust APIs for WasmEdge, a light-weight, high-performance, and extensible WebAssembly runtime for cloud-native, edge, and decentralized applications.

For developers, it is recommended that the APIs in wasmedge-sys are used to construct high-level libraries, while wasmedge-sdk is for building up business applications.

Notice that wasmedge-sdk requires Rust v1.63 or above in the stable channel.

Versioning Table

The following table provides the versioning information about each crate of WasmEdge Rust bindings.

Build

To use or build the wasmedge-sys crate, the WasmEdge library is required.

• If you choose to use install.sh to install WasmEdge Runtime on your local system. Please use WASMEDGE_INCLUDE_DIR and WASMEDGE_LIB_DIR to specify the paths to the include and lib directories, respectively. For example, use the following commands to specify the paths after using bash install.sh --path=$HOME/wasmedge-install to install WasmEdge Runtime on Ubuntu 20.04:

  export WASMEDGE_INCLUDE_DIR=$HOME/wasmedge-install/include 
  export WASMEDGE_LIB_DIR=$HOME/wasmedge-install/lib
  

• If you choose to manually download WasmEdge Runtime binary from WasmEdge Releases Page, it is strongly recommended to place it in $HOME/.wasmedge directory. It looks like below on Ubuntu 20.04. wasmedge-sys will search the directory automatically, you do not have to set any environment variables for it.

  // $HOME/.wasmedge/
  .
  |-- bin
  |   |-- wasmedge
  |   `-- wasmedgec
  |-- include
  |   `-- wasmedge
  |       |-- enum.inc
  |       |-- enum_configure.h
  |       |-- enum_errcode.h
  |       |-- enum_types.h
  |       |-- int128.h
  |       |-- version.h
  |       `-- wasmedge.h
  `-- lib64
      |-- libwasmedge_c.so
      `-- wasmedge
          `-- libwasmedgePluginWasmEdgeProcess.so
  
  5 directories, 11 files
  

Enable WasmEdge Plugins

If you'd like to enable WasmEdge Plugins (currently, only available on Linux platform), please use WASMEDGE_PLUGIN_PATH environment variable to specify the path to the directory containing the plugins. For example, use the following commands to specify the path on Ubuntu 20.04:

export WASMEDGE_PLUGIN_PATH=$HOME/.wasmedge/lib/wasmedge

Example

A quick-start example below is using wasmedge-sys to run a WebAssembly module written with its WAT format (textual format):

use wasmedge_sys::{Vm, WasmValue};
use wasmedge_types::wat2wasm;

#[cfg_attr(test, test)]
fn main() -> Result<(), Box<dyn std::error::Error>> {
    // read the wasm bytes
    let wasm_bytes = wat2wasm(
        br#"
        (module
            (export "fib" (func $fib))
            (func $fib (param $n i32) (result i32)
             (if
              (i32.lt_s
               (get_local $n)
               (i32.const 2)
              )
              (return
               (i32.const 1)
              )
             )
             (return
              (i32.add
               (call $fib
                (i32.sub
                 (get_local $n)
                 (i32.const 2)
                )
               )
               (call $fib
                (i32.sub
                 (get_local $n)
                 (i32.const 1)
                )
               )
              )
             )
            )
           )
"#,
    )?;

    // create a Vm instance
    let mut vm = Vm::create(None, None)?;

    // register the wasm bytes
    let module_name = "extern-module";
    vm.register_wasm_from_buffer(module_name, &wasm_bytes)?;

    // run the exported function named "fib"
    let func_name = "fib";
    let result = vm.run_registered_function(module_name, func_name, [WasmValue::from_i32(5)])?;

    assert_eq!(result.len(), 1);
    assert_eq!(result[0].to_i32(), 8);

    Ok(())
}

See also

• WasmEdge Runtime Official Website
• WasmEdge Docs
• WasmEdge C API Documentation