more emscripten stubs and urandom hack (#199)

lib/emscripten/src/syscalls/windows.rs

@@ -1,10 +1,62 @@
+use crate::utils::copy_cstr_into_wasm;
+use crate::utils::read_string_from_wasm;
 use crate::varargs::VarArgs;
 use libc::mkdir;
+use libc::open;
+use rand::Rng;
+use std::env;
+use std::ffi::CStr;
+use std::ffi::CString;
+use std::fs::File;
+use std::io::Write;
 use std::os::raw::c_int;
 use wasmer_runtime_core::vm::Ctx;
 
 type pid_t = c_int;
 
+/// open
+pub fn ___syscall5(ctx: &mut Ctx, which: c_int, mut varargs: VarArgs) -> c_int {
+    debug!("emscripten::___syscall5 (open) {}", which);
+    let pathname: u32 = varargs.get(ctx);
+    let flags: i32 = varargs.get(ctx);
+    let mode: u32 = varargs.get(ctx);
+    let pathname_addr = emscripten_memory_pointer!(ctx.memory(0), pathname) as *const i8;
+    let path_str = unsafe { std::ffi::CStr::from_ptr(pathname_addr).to_str().unwrap() };
+    match path_str {
+        "/dev/urandom" => {
+            // create a fake urandom file for windows, super hacky
+            // put it in the temp directory so we can just forget about it
+            let mut tmp_dir = env::temp_dir();
+            tmp_dir.push("urandom");
+            let tmp_dir_str = tmp_dir.to_str().unwrap();
+            let tmp_dir_c_str = CString::new(tmp_dir_str).unwrap();
+            let ptr = tmp_dir_c_str.as_ptr() as *const i8;
+            let mut urandom_file = File::create(tmp_dir).unwrap();
+            // create some random bytes and put them into the file
+            let random_bytes = rand::thread_rng().gen::<[u8; 32]>();
+            urandom_file.write_all(&random_bytes);
+            // put the file path string into wasm memory
+            let urandom_file_offset = unsafe { copy_cstr_into_wasm(ctx, ptr) };
+            let raw_pointer_to_urandom_file =
+                emscripten_memory_pointer!(ctx.memory(0), urandom_file_offset) as *const i8;
+            let fd = unsafe { open(raw_pointer_to_urandom_file, flags, mode) };
+            debug!(
+                "=> pathname: {}, flags: {}, mode: {} = fd: {}\npath: {}",
+                pathname, flags, mode, fd, s
+            );
+            fd
+        }
+        _ => {
+            let fd = unsafe { open(pathname_addr, flags, mode) };
+            debug!(
+                "=> pathname: {}, flags: {}, mode: {} = fd: {}\npath: {}",
+                pathname, flags, mode, fd, path_str
+            );
+            fd
+        }
+    }
+}
+
 // chown
 pub fn ___syscall212(ctx: &mut Ctx, which: c_int, mut varargs: VarArgs) -> c_int {
     debug!("emscripten::___syscall212 (chown) {}", which);