Introduce first groundwork for Wasm executor (#27)

* Introduce first groundwork for Wasm executor.

* Remove old Rust-runtime code.

* Avoid commiting compled files.

* Add runtime precompile.

* Rename so module makes more sense.

* Further renaming.

* Ensure tests work.

* Allow bringing in of externalities.

- Add util functions/macros.
- Add uncompacted runtime.
- Add some external crates from pwasm-std for managing allocs/memory
stuff.

* Nice macros for imports.

* Allow passing in of data through allocators.

Make memcpy and malloc work.
Basic allocator.

* Can now pass in bytes to WasmExecutor.

* Additional cleanup.

* Switch usages of `OutData` to `u64`

No need to be able to return bytes anymore.

* convert to safe but extremely verbose type conversion.

@rphmeier any more concise way of doing this?

* Remove StaticExternalities distinction.

* Remove another unused use.

* Refactor wasm utils out

* Remove extraneous copies that weren't really testing anything.

* Try to use wasm 0.15

* Make it work!

* Call-time externalities working.

* Add basic externalities.

* Fix grumbles and note unwraps to be sorted.

* Test storage externality.

Unforunately had to change signatures of externalities to avoid
immutable function returning a reference. Not sure what to do about
this...

* Fix nits.

* Compile collation logic.

* Move back to refs. Yey.

* Remove "object" id for storage access.

* Fix test.

* Fix up rest of tests.

* remove unwrap.

* Expose set/get code in externalities

Also improve tests and add nice wrappers in rust-wasm.

* Add validator set.

* Introduce validator set into externalities and test.

* Add another external function.

* Remove code and validators; use storage for everything.

* Introduce validators function.

* Tests (and a fix) for the validators getter.

* Allow calls into runtime to return data.

* Remove unneeded trace.

* Make runtime printing a bit nicer.

* Create separate runtimes for testing and polkadot.

* Remove commented code.

* Use new path.

* Refactor into shared support module.

* Fix warning.

* Remove unwraps.

* Make macro a little less unhygenic.

* Add wasm files.

substrate/runtime/support/src/lib.rs

@@ -0,0 +1,125 @@
+#![no_std]
+#![feature(lang_items)]
+#![cfg_attr(feature = "strict", deny(warnings))]
+
+#![feature(alloc)]
+
+extern crate alloc;
+use alloc::vec::Vec;
+
+extern crate pwasm_libc;
+extern crate pwasm_alloc;
+
+#[lang = "panic_fmt"]
+#[no_mangle]
+pub fn panic_fmt() -> ! {
+	  loop {}
+}
+
+extern "C" {
+	fn ext_print(utf8_data: *const u8, utf8_len: i32);
+	fn ext_print_num(value: u64);
+	fn ext_set_storage(key_data: *const u8, key_len: i32, value_data: *const u8, value_len: i32);
+	fn ext_get_allocated_storage(key_data: *const u8, key_len: i32, written_out: *mut i32) -> *mut u8;
+}
+
+pub fn storage(key: &[u8]) -> Vec<u8> {
+	let mut length: i32 = 0;
+	unsafe {
+		let ptr = ext_get_allocated_storage(&key[0], key.len() as i32, &mut length);
+		Vec::from_raw_parts(ptr, length as usize, length as usize)
+	}
+}
+
+pub fn set_storage(key: &[u8], value: &[u8]) {
+	unsafe {
+		ext_set_storage(
+			&key[0] as *const u8, key.len() as i32,
+			&value[0] as *const u8, value.len() as i32
+		);
+	}
+}
+
+pub fn code() -> Vec<u8> {
+	storage(b"\0code")
+}
+
+pub fn set_code(new: &[u8]) {
+	set_storage(b"\0code", new)
+}
+
+fn value_vec(mut value: usize, initial: Vec<u8>) -> Vec<u8> {
+	let mut acc = initial;
+	while value > 0 {
+		acc.push(value as u8);
+		value /= 256;
+	}
+	acc
+}
+
+pub fn set_validator(index: usize, validator: &[u8]) {
+	set_storage(&value_vec(index, b"\0validator".to_vec()), validator);
+}
+
+pub fn validator(index: usize) -> Vec<u8> {
+	storage(&value_vec(index, b"\0validator".to_vec()))
+}
+
+pub fn set_validator_count(count: usize) {
+	(count..validator_count()).for_each(|i| set_validator(i, &[]));
+	set_storage(b"\0validator_count", &value_vec(count, Vec::new()));
+}
+
+pub fn validator_count() -> usize {
+	storage(b"\0validator_count").into_iter().rev().fold(0, |acc, i| (acc << 8) + (i as usize))
+}
+
+pub fn validators() -> Vec<Vec<u8>> {
+	(0..validator_count()).into_iter().map(validator).collect()
+}
+
+pub fn set_validators(validators: &[&[u8]]) {
+	set_validator_count(validators.len());
+	validators.iter().enumerate().for_each(|(v, i)| set_validator(v, i));
+}
+
+pub trait Printable {
+	fn print(self);
+}
+
+impl<'a> Printable for &'a [u8] {
+	fn print(self) {
+		unsafe {
+			ext_print(&self[0] as *const u8, self.len() as i32);
+		}
+	}
+}
+
+impl Printable for u64 {
+	fn print(self) {
+		unsafe { ext_print_num(self); }
+	}
+}
+
+pub fn print<T: Printable + Sized>(value: T) {
+	value.print();
+}
+
+#[macro_export]
+macro_rules! impl_stub {
+	($name:ident) => {
+		pub mod _internal {
+			extern crate alloc;
+			
+			#[no_mangle]
+			pub fn $name(input_data: *mut u8, input_len: usize) -> u64 {
+				let input = unsafe {
+					::alloc::vec::Vec::from_raw_parts(input_data, input_len, input_len)
+				};
+
+				let output = super::$name(input);
+				&output[0] as *const u8 as u64 + ((output.len() as u64) << 32)
+			}
+		}
+	}
+}