1 files changed, 45 insertions, 0 deletions
diff --git a/library/stdarch/examples/wasm.rs b/library/stdarch/examples/wasm.rs
new file mode 100644
index 000000000..6b92ae9b8
--- /dev/null
+++ b/library/stdarch/examples/wasm.rs
@@ -0,0 +1,45 @@
+//! A simple slab allocator for pages in wasm
+
+#![feature(stdsimd)]
+#![cfg(target_arch = "wasm32")]
+
+use std::ptr;
+
+use core_arch::arch::wasm32::*;
+
+static mut HEAD: *mut *mut u8 = 0 as _;
+
+#[no_mangle]
+pub unsafe extern "C" fn page_alloc() -> *mut u8 {
+    if !HEAD.is_null() {
+        let next = *HEAD;
+        let ret = HEAD;
+        HEAD = next as *mut _;
+        return ret as *mut u8;
+    }
+
+    let ret = memory_grow(0, 1);
+
+    // if we failed to allocate a page then return null
+    if ret == usize::MAX {
+        return ptr::null_mut();
+    }
+
+    ((ret as u32) * page_size()) as *mut u8
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn page_free(page: *mut u8) {
+    let page = page as *mut *mut u8;
+    *page = HEAD as *mut u8;
+    HEAD = page;
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn memory_used() -> usize {
+    (page_size() * (memory_size(0) as u32)) as usize
+}
+
+fn page_size() -> u32 {
+    64 * 1024
+}