Isolated emscripten in new lib

lib/emscripten/src/memory.rs

@@ -0,0 +1,48 @@
+use super::process::abort_with_message;
+use wasmer_runtime::Instance;
+use libc::{c_int, c_void, memcpy, size_t};
+
+/// emscripten: _emscripten_memcpy_big
+pub extern "C" fn _emscripten_memcpy_big(
+    dest: u32,
+    src: u32,
+    len: u32,
+    instance: &mut Instance,
+) -> u32 {
+    debug!(
+        "emscripten::_emscripten_memcpy_big {}, {}, {}",
+        dest, src, len
+    );
+    let dest_addr = instance.memory_offset_addr(0, dest as usize) as *mut c_void;
+    let src_addr = instance.memory_offset_addr(0, src as usize) as *mut c_void;
+    unsafe {
+        memcpy(dest_addr, src_addr, len as size_t);
+    }
+    dest
+}
+
+/// emscripten: getTotalMemory
+pub extern "C" fn get_total_memory(_instance: &mut Instance) -> u32 {
+    debug!("emscripten::get_total_memory");
+    // instance.memories[0].current_pages()
+    16_777_216
+}
+
+/// emscripten: enlargeMemory
+pub extern "C" fn enlarge_memory(_instance: &mut Instance) {
+    debug!("emscripten::enlarge_memory");
+    // instance.memories[0].grow(100);
+}
+
+/// emscripten: abortOnCannotGrowMemory
+pub extern "C" fn abort_on_cannot_grow_memory() {
+    debug!("emscripten::abort_on_cannot_grow_memory");
+    abort_with_message("Cannot enlarge memory arrays!");
+}
+
+/// emscripten: ___map_file
+pub extern "C" fn ___map_file() -> c_int {
+    debug!("emscripten::___map_file");
+    // NOTE: TODO: Em returns -1 here as well. May need to implement properly
+    -1
+}