Initial reorg.

This is largely the same as #305, but updated for the current tree.

crates/misc/py/examples/import/.gitignore

@@ -0,0 +1,3 @@
+import.wasm
+main.wasm
+__pycache__

crates/misc/py/examples/import/README.md

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+# Build example's file
+
+To build `demo.wasm` use rustc (nightly) for wasm32 target with debug information:
+
+```
+rustc +nightly --target=wasm32-unknown-unknown demo.rs --crate-type=cdylib
+```
+
+# Run example
+
+Point path to the built `wasmtime_py` library location when running python, e.g.
+
+```
+PYTHONPATH=../../target/debug python3 run.py
+```

crates/misc/py/examples/import/demo.rs

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+extern "C" {
+    fn callback(s: *const u8, s_len: u32) -> u32;
+}
+
+#[no_mangle]
+pub extern "C" fn test() {
+    let msg = "Hello, world!";
+    unsafe {
+        callback(msg.as_ptr(), msg.len() as u32);
+    }
+}

crates/misc/py/examples/import/env.py

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+def callback(msg_p: 'i32', msg_len: 'i32') -> 'i32':
+    print('callback:', msg_p, msg_len)
+
+#    global memory
+#    mv = memoryview(memory)
+
+#    msg = bytes(mv[msg_p:(msg_p + msg_len)]).decode('utf-8')
+#    print(msg)
+
+    return 42

crates/misc/py/examples/import/run.py

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+import wasmtime
+import demo
+
+demo.test()