Implement WASI C API.
This commit implements an initial WASI C API that can be used to instantiate and configure a WASI instance from C. This also implements a `WasiBuilder` for the C# API enabling .NET hosts to bind to Wasmtime's WASI implementation.
This commit is contained in:
Peter Huene
274
crates/c-api/src/wasi.rs
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274
crates/c-api/src/wasi.rs
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//! The WASI embedding API definitions for Wasmtime.
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use crate::{wasm_extern_t, wasm_importtype_t, wasm_store_t, wasm_trap_t, ExternHost, ExternType};
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use std::collections::HashMap;
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use std::ffi::CStr;
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use std::fs::File;
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use std::os::raw::{c_char, c_int};
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use std::path::Path;
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use std::slice;
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use wasi_common::{preopen_dir, WasiCtxBuilder};
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use wasmtime::{HostRef, Trap};
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use wasmtime_wasi::Wasi;
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unsafe fn cstr_to_path<'a>(path: *const c_char) -> Option<&'a Path> {
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CStr::from_ptr(path).to_str().map(Path::new).ok()
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}
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unsafe fn open_file(path: *const c_char) -> Option<File> {
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File::open(cstr_to_path(path)?).ok()
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}
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unsafe fn create_file(path: *const c_char) -> Option<File> {
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File::create(cstr_to_path(path)?).ok()
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}
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#[repr(C)]
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pub struct wasi_config_t {
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builder: WasiCtxBuilder,
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}
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impl wasi_config_t {}
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#[no_mangle]
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pub unsafe extern "C" fn wasi_config_new() -> *mut wasi_config_t {
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Box::into_raw(Box::new(wasi_config_t {
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builder: WasiCtxBuilder::new(),
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}))
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}
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#[no_mangle]
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pub unsafe extern "C" fn wasi_config_delete(config: *mut wasi_config_t) {
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drop(Box::from_raw(config));
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}
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#[no_mangle]
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pub unsafe extern "C" fn wasi_config_set_argv(
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config: *mut wasi_config_t,
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argc: c_int,
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argv: *const *const c_char,
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) {
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let mut config = Box::from_raw(config);
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config.builder = config.builder.args(
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slice::from_raw_parts(argv, argc as usize)
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.iter()
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.map(|a| slice::from_raw_parts(*a as *const u8, CStr::from_ptr(*a).to_bytes().len())),
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);
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std::mem::forget(config);
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}
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#[no_mangle]
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pub unsafe extern "C" fn wasi_config_inherit_argv(config: *mut wasi_config_t) {
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let mut config = Box::from_raw(config);
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config.builder = config.builder.inherit_args();
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std::mem::forget(config);
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}
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#[no_mangle]
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pub unsafe extern "C" fn wasi_config_set_env(
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config: *mut wasi_config_t,
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envc: c_int,
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names: *const *const c_char,
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values: *const *const c_char,
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) {
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let names = slice::from_raw_parts(names, envc as usize);
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let values = slice::from_raw_parts(values, envc as usize);
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let mut config = Box::from_raw(config);
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for i in 0..envc as usize {
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config.builder = config.builder.env(
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CStr::from_ptr(names[i]).to_bytes(),
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CStr::from_ptr(values[i]).to_bytes(),
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);
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}
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std::mem::forget(config);
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}
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#[no_mangle]
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pub unsafe extern "C" fn wasi_config_inherit_env(config: *mut wasi_config_t) {
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let mut config = Box::from_raw(config);
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config.builder = config.builder.inherit_env();
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std::mem::forget(config);
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}
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#[no_mangle]
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pub unsafe extern "C" fn wasi_config_set_stdin(
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config: *mut wasi_config_t,
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path: *const c_char,
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) -> bool {
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let file = match open_file(path) {
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Some(f) => f,
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None => return false,
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};
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let mut config = Box::from_raw(config);
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config.builder = config.builder.stdin(file);
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std::mem::forget(config);
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true
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}
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#[no_mangle]
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pub unsafe extern "C" fn wasi_config_inherit_stdin(config: *mut wasi_config_t) {
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let mut config = Box::from_raw(config);
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config.builder = config.builder.inherit_stdin();
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std::mem::forget(config);
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}
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#[no_mangle]
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pub unsafe extern "C" fn wasi_config_set_stdout(
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config: *mut wasi_config_t,
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path: *const c_char,
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) -> bool {
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let file = match create_file(path) {
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Some(f) => f,
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None => return false,
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};
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let mut config = Box::from_raw(config);
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config.builder = config.builder.stdout(file);
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std::mem::forget(config);
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true
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}
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#[no_mangle]
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pub unsafe extern "C" fn wasi_config_inherit_stdout(config: *mut wasi_config_t) {
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let mut config = Box::from_raw(config);
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config.builder = config.builder.inherit_stdout();
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std::mem::forget(config);
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}
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#[no_mangle]
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pub unsafe extern "C" fn wasi_config_set_stderr(
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config: *mut wasi_config_t,
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path: *const c_char,
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) -> bool {
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let file = match create_file(path) {
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Some(f) => f,
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None => return false,
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};
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let mut config = Box::from_raw(config);
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config.builder = config.builder.stderr(file);
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std::mem::forget(config);
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true
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}
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#[no_mangle]
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pub unsafe extern "C" fn wasi_config_inherit_stderr(config: *mut wasi_config_t) {
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let mut config = Box::from_raw(config);
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config.builder = config.builder.inherit_stderr();
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std::mem::forget(config);
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}
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#[no_mangle]
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pub unsafe extern "C" fn wasi_config_preopen_dir(
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config: *mut wasi_config_t,
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path: *const c_char,
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guest_path: *const c_char,
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) -> bool {
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let guest_path = match cstr_to_path(guest_path) {
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Some(p) => p,
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None => return false,
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};
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let dir = match cstr_to_path(path) {
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Some(p) => match preopen_dir(p) {
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Ok(d) => d,
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Err(_) => return false,
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},
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None => return false,
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};
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let mut config = Box::from_raw(config);
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config.builder = config.builder.preopened_dir(dir, guest_path);
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std::mem::forget(config);
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true
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}
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#[repr(C)]
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pub struct wasi_instance_t {
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wasi: Wasi,
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export_cache: HashMap<String, *mut wasm_extern_t>,
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}
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impl Drop for wasi_instance_t {
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fn drop(&mut self) {
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for v in self.export_cache.values() {
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drop(unsafe { Box::from_raw(*v) });
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}
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}
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}
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#[no_mangle]
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pub unsafe extern "C" fn wasi_instance_new(
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store: *mut wasm_store_t,
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config: *mut wasi_config_t,
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trap: *mut *mut wasm_trap_t,
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) -> *mut wasi_instance_t {
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let store = &(*store).store.borrow();
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let config = Box::from_raw(config);
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match config.builder.build() {
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Ok(ctx) => Box::into_raw(Box::new(wasi_instance_t {
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wasi: Wasi::new(store, ctx),
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export_cache: HashMap::new(),
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})),
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Err(e) => {
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(*trap) = Box::into_raw(Box::new(wasm_trap_t {
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trap: HostRef::new(Trap::new(e.to_string())),
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}));
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std::ptr::null_mut()
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}
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}
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}
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#[no_mangle]
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pub unsafe extern "C" fn wasi_instance_delete(instance: *mut wasi_instance_t) {
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drop(Box::from_raw(instance));
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}
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#[no_mangle]
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pub unsafe extern "C" fn wasi_instance_bind_import(
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instance: *mut wasi_instance_t,
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import: *const wasm_importtype_t,
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) -> *const wasm_extern_t {
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// TODO: support previous versions?
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if (*import).ty.module() != "wasi_snapshot_preview1" {
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return std::ptr::null_mut();
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}
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// The import should be a function (WASI only exports functions)
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let func_type = match (*import).ty.ty() {
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ExternType::Func(f) => f,
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_ => return std::ptr::null_mut(),
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};
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let name = (*import).ty.name();
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match (*instance).wasi.get_export(name) {
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Some(export) => {
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if export.ty().params() != func_type.params() {
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return std::ptr::null_mut();
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}
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if export.ty().results() != func_type.results() {
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return std::ptr::null_mut();
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}
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*(*instance)
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.export_cache
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.entry(name.to_string())
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.or_insert_with(|| {
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Box::into_raw(Box::new(wasm_extern_t {
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which: ExternHost::Func(HostRef::new(export.clone())),
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}))
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})
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}
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None => std::ptr::null_mut(),
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}
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}
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