add mapdir for emscripten; implement getdents, etc.

lib/emscripten/src/utils.rs

@@ -5,6 +5,7 @@ use libc::stat;
 use std::ffi::CStr;
 use std::mem::size_of;
 use std::os::raw::c_char;
+use std::path::PathBuf;
 use std::slice;
 use wasmer_runtime_core::memory::Memory;
 use wasmer_runtime_core::{
@@ -204,6 +205,37 @@ pub fn read_string_from_wasm(memory: &Memory, offset: u32) -> String {
     String::from_utf8_lossy(&v).to_owned().to_string()
 }
 
+/// This function trys to find an entry in mapdir
+/// translating paths into their correct value
+pub fn get_cstr_path(ctx: &mut Ctx, path: *const i8) -> Option<std::ffi::CString> {
+    let path_str = unsafe { std::ffi::CStr::from_ptr(path).to_str().unwrap() }.to_string();
+    if let Some(val) = get_emscripten_data(ctx).mapped_dirs.get(&path_str) {
+        std::ffi::CString::new(val.to_string_lossy().as_bytes()).ok()
+    } else {
+        None
+    }
+}
+
+/// gets the current directory
+/// handles mapdir logic
+pub fn get_current_directory(ctx: &mut Ctx) -> Option<PathBuf> {
+    if let Some(val) = get_emscripten_data(ctx).mapped_dirs.get(".") {
+        return Some(val.clone());
+    }
+    std::env::current_dir()
+        .map(|cwd| {
+            if let Some(val) = get_emscripten_data(ctx)
+                .mapped_dirs
+                .get(&cwd.to_string_lossy().to_string())
+            {
+                val.clone()
+            } else {
+                cwd
+            }
+        })
+        .ok()
+}
+
 #[cfg(test)]
 mod tests {
     use super::is_emscripten_module;