mirror of
https://github.com/fluencelabs/wasm-bindgen
synced 2025-06-13 13:01:22 +00:00
Add an example of wasm2asm and wasm-bindgen
This commit adds an example of executing the `wasm2asm` tool to generate asm.js output instead of WebAssembly. This is often useful when supporting older browsers, such as IE 11, that doesn't have native support for WebAssembly.
This commit is contained in:
Alex Crichton
@ -1,18 +1,24 @@
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extern crate base64;
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extern crate tempfile;
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use std::collections::HashSet;
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use std::collections::{HashSet, HashMap};
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use std::fs::File;
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use std::io::{self, Write, Read};
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use std::process::Command;
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use parity_wasm::elements::*;
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use failure::Error;
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use failure::{Error, ResultExt};
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pub struct Config {
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base64: bool,
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wasm2asm: bool,
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fetch_path: Option<String>,
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}
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pub struct Output {
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module: Module,
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base64: bool,
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wasm2asm: bool,
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fetch_path: Option<String>,
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}
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@ -20,6 +26,7 @@ impl Config {
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pub fn new() -> Config {
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Config {
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base64: false,
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wasm2asm: false,
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fetch_path: None,
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}
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}
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@ -29,19 +36,25 @@ impl Config {
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self
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}
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pub fn wasm2asm(&mut self, wasm2asm: bool) -> &mut Self {
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self.wasm2asm = wasm2asm;
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self
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}
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pub fn fetch(&mut self, path: Option<String>) -> &mut Self {
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self.fetch_path = path;
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self
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}
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pub fn generate(&mut self, wasm: &[u8]) -> Result<Output, Error> {
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if !self.base64 && !self.fetch_path.is_some() {
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bail!("the option --base64 or --fetch is required");
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if !self.base64 && !self.fetch_path.is_some() && !self.wasm2asm {
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bail!("one of --base64, --fetch, or --wasm2asm is required");
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}
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let module = deserialize_buffer(wasm)?;
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Ok(Output {
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module,
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base64: self.base64,
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wasm2asm: self.wasm2asm,
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fetch_path: self.fetch_path.clone(),
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})
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}
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@ -108,6 +121,9 @@ impl Output {
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}
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pub fn js(self) -> Result<String, Error> {
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if self.wasm2asm {
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return self.js_wasm2asm();
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}
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let mut js_imports = String::new();
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let mut exports = String::new();
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let mut imports = String::new();
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@ -235,4 +251,190 @@ impl Output {
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mem_export = if export_mem { "export let memory;" } else { "" },
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))
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}
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fn js_wasm2asm(self) -> Result<String, Error> {
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let mut js_imports = String::new();
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let mut imported_modules = Vec::new();
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if let Some(i) = self.module.import_section() {
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let mut module_set = HashSet::new();
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let mut name_map = HashMap::new();
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for entry in i.entries() {
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match *entry.external() {
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External::Function(_) => {}
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External::Table(_) => {
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bail!("wasm imports a table which isn't supported yet");
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}
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External::Memory(_) => {
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bail!("wasm imports memory which isn't supported yet");
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}
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External::Global(_) => {
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bail!("wasm imports globals which aren't supported yet");
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}
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}
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let m = name_map.entry(entry.field()).or_insert(entry.module());
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if *m != entry.module() {
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bail!("the name `{}` is imported from two differnet \
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modules which currently isn't supported in `wasm2asm` \
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mode");
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}
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if !module_set.insert(entry.module()) {
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continue
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}
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let name = (b'a' + (module_set.len() as u8)) as char;
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js_imports.push_str(&format!("import * as import_{} from '{}';",
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name,
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entry.module()));
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imported_modules.push(format!("import_{}", name));
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}
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}
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let mut js_exports = String::new();
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if let Some(i) = self.module.export_section() {
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let mut export_mem = false;
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for entry in i.entries() {
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match *entry.internal() {
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Internal::Function(_) => {}
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Internal::Memory(_) => export_mem = true,
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Internal::Table(_) => continue,
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Internal::Global(_) => continue,
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};
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js_exports.push_str(&format!("export const {0} = ret.{0};\n",
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entry.field()));
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}
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if !export_mem {
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bail!("the `wasm2asm` mode is currently only compatible with \
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modules that export memory")
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}
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}
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let memory_size = self.module.memory_section()
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.unwrap()
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.entries()[0]
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.limits()
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.initial();
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let mut js_init_mem = String::new();
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if let Some(s) = self.module.data_section() {
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for entry in s.entries() {
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let offset = entry.offset().code();
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if offset.len() != 2 {
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bail!("don't recognize data offset {:?}", offset)
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}
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if offset[1] != Opcode::End {
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bail!("don't recognize data offset {:?}", offset)
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}
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let offset = match offset[0] {
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Opcode::I32Const(x) => x,
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_ => bail!("don't recognize data offset {:?}", offset),
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};
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let base64 = base64::encode(entry.value());
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js_init_mem.push_str(&format!("_assign({}, \"{}\");\n",
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offset,
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base64));
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}
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}
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let td = tempfile::tempdir()?;
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let wasm = serialize(self.module)?;
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let wasm_file = td.as_ref().join("foo.wasm");
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File::create(&wasm_file)
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.and_then(|mut f| f.write_all(&wasm))
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.with_context(|_| {
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format!("failed to write wasm to `{}`", wasm_file.display())
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})?;
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let wast_file = td.as_ref().join("foo.wast");
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run(
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Command::new("wasm-dis")
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.arg(&wasm_file)
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.arg("-o")
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.arg(&wast_file),
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"wasm-dis",
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)?;
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let js_file = td.as_ref().join("foo.js");
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run(
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Command::new("wasm2asm")
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.arg(&wast_file)
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.arg("-o")
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.arg(&js_file),
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"wasm2asm",
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)?;
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let mut asm_func = String::new();
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File::open(&js_file)
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.and_then(|mut f| f.read_to_string(&mut asm_func))
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.with_context(|_| {
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format!("failed to read `{}`", js_file.display())
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})?;
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let mut imports = String::from("{}");
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for m in imported_modules {
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imports = format!("Object.assign({}, {})", imports, m);
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}
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Ok(format!("\
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{js_imports}
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{asm_func}
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const mem = new ArrayBuffer({mem_size});
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const _mem = new Uint8Array(mem);
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function _assign(offset, s) {{
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if (typeof Buffer === 'undefined') {{
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const bytes = atob(s);
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for (let i = 0; i < bytes.length; i++)
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_mem[offset + i] = bytes.charCodeAt(i);
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}} else {{
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const bytes = Buffer.from(s, 'base64');
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for (let i = 0; i < bytes.length; i++)
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_mem[offset + i] = bytes[i];
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}}
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}}
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{js_init_mem}
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const ret = asmFunc(self, {imports}, mem);
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{js_exports}
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",
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js_imports = js_imports,
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js_init_mem = js_init_mem,
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asm_func = asm_func,
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js_exports = js_exports,
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imports = imports,
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mem_size = memory_size * (1 << 16),
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))
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}
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}
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fn run(cmd: &mut Command, program: &str) -> Result<(), Error> {
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let output = cmd.output().with_context(|e| {
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if e.kind() == io::ErrorKind::NotFound {
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format!("failed to execute `{}`, is the tool installed \
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from the binaryen project?\ncommand line: {:?}",
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program,
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cmd)
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} else {
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format!("failed to execute: {:?}", cmd)
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}
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})?;
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if output.status.success() {
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return Ok(())
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}
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let mut s = format!("failed to execute: {:?}\nstatus: {}\n",
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cmd,
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output.status);
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if !output.stdout.is_empty() {
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s.push_str(&format!("----- stdout ------\n{}\n",
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String::from_utf8_lossy(&output.stdout)));
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}
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if !output.stderr.is_empty() {
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s.push_str(&format!("----- stderr ------\n{}\n",
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String::from_utf8_lossy(&output.stderr)));
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}
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bail!("{}", s)
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}
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