Add a Module::deserialize_file method (#3266)

* Add a `Module::deserialize_file` method

This commit adds a new method to the `wasmtime::Module` type,
`deserialize_file`. This is intended to be the same as the `deserialize`
method except for the serialized module is present as an on-disk file.
This enables Wasmtime to internally use `mmap` to avoid copying bytes
around and generally makes loading a module much faster.

A C API is added in this commit as well for various bindings to use this
accelerated path now as well. Another option perhaps for a Rust-based
API is to have an API taking a `File` itself to allow for a custom file
descriptor in one way or another, but for now that's left for a possible
future refactoring if we find a use case.

* Fix compat with main - handle readdonly mmap

* wip

* Try to fix Windows support

crates/c-api/src/module.rs

@@ -3,6 +3,9 @@ use crate::{
     wasm_extern_t, wasm_importtype_t, wasm_importtype_vec_t, wasm_store_t, wasmtime_error_t,
     wasmtime_moduletype_t, StoreRef,
 };
+use anyhow::Context;
+use std::ffi::CStr;
+use std::os::raw::c_char;
 use wasmtime::{Engine, Extern, Module};
 
 #[derive(Clone)]
@@ -202,3 +205,19 @@ pub unsafe extern "C" fn wasmtime_module_deserialize(
         *out = Box::into_raw(Box::new(wasmtime_module_t { module }));
     })
 }
+
+#[no_mangle]
+pub unsafe extern "C" fn wasmtime_module_deserialize_file(
+    engine: &wasm_engine_t,
+    path: *const c_char,
+    out: &mut *mut wasmtime_module_t,
+) -> Option<Box<wasmtime_error_t>> {
+    let path = CStr::from_ptr(path);
+    let result = path
+        .to_str()
+        .context("input path is not valid utf-8")
+        .and_then(|path| Module::deserialize_file(&engine.engine, path));
+    handle_result(result, |module| {
+        *out = Box::into_raw(Box::new(wasmtime_module_t { module }));
+    })
+}