Wasmer cache example

wasmer_cache.rs

// This is an example on how a cache system could work.
// It enforces a very useful pattern for caching:
// - serializing (cache.save)
// - deserializing (cache.load)

// This abstracts the responsibility on how to load or how to save
// outside, so it can be a FileSystem, a HashMap in memory, ...

// We get the hash from the binary
let hash: WasmHash = get_wasm_hash(&wasm_binary);

// We create a new cache instance.
// It could be possible to use any other kinds of caching, as long as they
// implement the Cache trait (with save and load functions)
let cache = FileSystemCache::new(WASMER_CACHE_DIR);

// cache.load will return the Module if it's able to deserialize it properly, and an error if:
// * The file is not found
// * The file exists, but it's corrupted or can't be converted to a module
let module = cache.load(hash).unwrap_or_else(|err| {
    let module = webassembly::compile(&wasm_binary[..])
        .map_err(|e| format!("Can't compile module: {:?}", e))?;

    // We save the module into a cache file
    cache.save(hash, module).unwrap();
    module
});