1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
// This file is part of Substrate.

// Copyright (C) 2019-2021 Parity Technologies (UK) Ltd.
// SPDX-License-Identifier: Apache-2.0

// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// 	http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

//! Types and traits for interfacing between the host and the wasm runtime.

#![cfg_attr(not(feature = "std"), no_std)]

use sp_std::{
	vec,
	borrow::Cow, marker::PhantomData, mem, iter::Iterator, result, vec::Vec,
};

#[cfg(feature = "std")]
mod wasmi_impl;

/// Result type used by traits in this crate.
#[cfg(feature = "std")]
pub type Result<T> = result::Result<T, String>;
#[cfg(not(feature = "std"))]
pub type Result<T> = result::Result<T, &'static str>;

/// Value types supported by Substrate on the boundary between host/Wasm.
#[derive(Copy, Clone, PartialEq, Debug, Eq)]
pub enum ValueType {
	/// An `i32` value type.
	I32,
	/// An `i64` value type.
	I64,
	/// An `f32` value type.
	F32,
	/// An `f64` value type.
	F64,
}

impl From<ValueType> for u8 {
	fn from(val: ValueType) -> u8 {
		match val {
			ValueType::I32 => 0,
			ValueType::I64 => 1,
			ValueType::F32 => 2,
			ValueType::F64 => 3,
		}
	}
}

impl sp_std::convert::TryFrom<u8> for ValueType {
	type Error = ();

	fn try_from(val: u8) -> sp_std::result::Result<ValueType, ()> {
		match val {
			0 => Ok(Self::I32),
			1 => Ok(Self::I64),
			2 => Ok(Self::F32),
			3 => Ok(Self::F64),
			_ => Err(()),
		}
	}
}

/// Values supported by Substrate on the boundary between host/Wasm.
#[derive(PartialEq, Debug, Clone, Copy, codec::Encode, codec::Decode)]
pub enum Value {
	/// A 32-bit integer.
	I32(i32),
	/// A 64-bit integer.
	I64(i64),
	/// A 32-bit floating-point number stored as raw bit pattern.
	///
	/// You can materialize this value using `f32::from_bits`.
	F32(u32),
	/// A 64-bit floating-point number stored as raw bit pattern.
	///
	/// You can materialize this value using `f64::from_bits`.
	F64(u64),
}

impl Value {
	/// Returns the type of this value.
	pub fn value_type(&self) -> ValueType {
		match self {
			Value::I32(_) => ValueType::I32,
			Value::I64(_) => ValueType::I64,
			Value::F32(_) => ValueType::F32,
			Value::F64(_) => ValueType::F64,
		}
	}

	/// Return `Self` as `i32`.
	pub fn as_i32(&self) -> Option<i32> {
		match self {
			Self::I32(val) => Some(*val),
			_ => None,
		}
	}
}

/// Provides `Sealed` trait to prevent implementing trait `PointerType` outside of this crate.
mod private {
	pub trait Sealed {}

	impl Sealed for u8 {}
	impl Sealed for u16 {}
	impl Sealed for u32 {}
	impl Sealed for u64 {}
}

/// Something that can be wrapped in a wasm `Pointer`.
///
/// This trait is sealed.
pub trait PointerType: Sized + private::Sealed {
	/// The size of the type in wasm.
	const SIZE: u32 = mem::size_of::<Self>() as u32;
}

impl PointerType for u8 {}
impl PointerType for u16 {}
impl PointerType for u32 {}
impl PointerType for u64 {}

/// Type to represent a pointer in wasm at the host.
#[derive(Debug, PartialEq, Eq, Clone, Copy)]
pub struct Pointer<T: PointerType> {
	ptr: u32,
	_marker: PhantomData<T>,
}

impl<T: PointerType> Pointer<T> {
	/// Create a new instance of `Self`.
	pub fn new(ptr: u32) -> Self {
		Self {
			ptr,
			_marker: Default::default(),
		}
	}

	/// Calculate the offset from this pointer.
	///
	/// `offset` is in units of `T`. So, `3` means `3 * mem::size_of::<T>()` as offset to the pointer.
	///
	/// Returns an `Option` to respect that the pointer could probably overflow.
	pub fn offset(self, offset: u32) -> Option<Self> {
		offset.checked_mul(T::SIZE).and_then(|o| self.ptr.checked_add(o)).map(|ptr| {
			Self {
				ptr,
				_marker: Default::default(),
			}
		})
	}

	/// Create a null pointer.
	pub fn null() -> Self {
		Self::new(0)
	}

	/// Cast this pointer of type `T` to a pointer of type `R`.
	pub fn cast<R: PointerType>(self) -> Pointer<R> {
		Pointer::new(self.ptr)
	}
}

impl<T: PointerType> From<u32> for Pointer<T> {
	fn from(ptr: u32) -> Self {
		Pointer::new(ptr)
	}
}

impl<T: PointerType> From<Pointer<T>> for u32 {
	fn from(ptr: Pointer<T>) -> Self {
		ptr.ptr
	}
}

impl<T: PointerType> From<Pointer<T>> for u64 {
	fn from(ptr: Pointer<T>) -> Self {
		u64::from(ptr.ptr)
	}
}

impl<T: PointerType> From<Pointer<T>> for usize {
	fn from(ptr: Pointer<T>) -> Self {
		ptr.ptr as _
	}
}

impl<T: PointerType> IntoValue for Pointer<T> {
	const VALUE_TYPE: ValueType = ValueType::I32;
	fn into_value(self) -> Value { Value::I32(self.ptr as _) }
}

impl<T: PointerType> TryFromValue for Pointer<T> {
	fn try_from_value(val: Value) -> Option<Self> {
		match val {
			Value::I32(val) => Some(Self::new(val as _)),
			_ => None,
		}
	}
}

/// The word size used in wasm. Normally known as `usize` in Rust.
pub type WordSize = u32;

/// The Signature of a function
#[derive(Eq, PartialEq, Debug, Clone)]
pub struct Signature {
	/// The arguments of a function.
	pub args: Cow<'static, [ValueType]>,
	/// The optional return value of a function.
	pub return_value: Option<ValueType>,
}

impl Signature {
	/// Create a new instance of `Signature`.
	pub fn new<T: Into<Cow<'static, [ValueType]>>>(args: T, return_value: Option<ValueType>) -> Self {
		Self {
			args: args.into(),
			return_value,
		}
	}

	/// Create a new instance of `Signature` with the given `args` and without any return value.
	pub fn new_with_args<T: Into<Cow<'static, [ValueType]>>>(args: T) -> Self {
		Self {
			args: args.into(),
			return_value: None,
		}
	}
}

/// A trait that requires `RefUnwindSafe` when `feature = std`.
#[cfg(feature = "std")]
pub trait MaybeRefUnwindSafe: std::panic::RefUnwindSafe {}
#[cfg(feature = "std")]
impl<T: std::panic::RefUnwindSafe> MaybeRefUnwindSafe for T {}

/// A trait that requires `RefUnwindSafe` when `feature = std`.
#[cfg(not(feature = "std"))]
pub trait MaybeRefUnwindSafe {}
#[cfg(not(feature = "std"))]
impl<T> MaybeRefUnwindSafe for T {}

/// Something that provides a function implementation on the host for a wasm function.
pub trait Function: MaybeRefUnwindSafe + Send + Sync {
	/// Returns the name of this function.
	fn name(&self) -> &str;
	/// Returns the signature of this function.
	fn signature(&self) -> Signature;
	/// Execute this function with the given arguments.
	fn execute(
		&self,
		context: &mut dyn FunctionContext,
		args: &mut dyn Iterator<Item = Value>,
	) -> Result<Option<Value>>;
}

impl PartialEq for dyn Function {
	fn eq(&self, other: &Self) -> bool {
		other.name() == self.name() && other.signature() == self.signature()
	}
}

/// Context used by `Function` to interact with the allocator and the memory of the wasm instance.
pub trait FunctionContext {
	/// Read memory from `address` into a vector.
	fn read_memory(&self, address: Pointer<u8>, size: WordSize) -> Result<Vec<u8>> {
		let mut vec = vec![0; size as usize];
		self.read_memory_into(address, &mut vec)?;
		Ok(vec)
	}
	/// Read memory into the given `dest` buffer from `address`.
	fn read_memory_into(&self, address: Pointer<u8>, dest: &mut [u8]) -> Result<()>;
	/// Write the given data at `address` into the memory.
	fn write_memory(&mut self, address: Pointer<u8>, data: &[u8]) -> Result<()>;
	/// Allocate a memory instance of `size` bytes.
	fn allocate_memory(&mut self, size: WordSize) -> Result<Pointer<u8>>;
	/// Deallocate a given memory instance.
	fn deallocate_memory(&mut self, ptr: Pointer<u8>) -> Result<()>;
	/// Provides access to the sandbox.
	fn sandbox(&mut self) -> &mut dyn Sandbox;
}

/// Sandbox memory identifier.
pub type MemoryId = u32;

/// Something that provides access to the sandbox.
pub trait Sandbox {
	/// Get sandbox memory from the `memory_id` instance at `offset` into the given buffer.
	fn memory_get(
		&mut self,
		memory_id: MemoryId,
		offset: WordSize,
		buf_ptr: Pointer<u8>,
		buf_len: WordSize,
	) -> Result<u32>;
	/// Set sandbox memory from the given value.
	fn memory_set(
		&mut self,
		memory_id: MemoryId,
		offset: WordSize,
		val_ptr: Pointer<u8>,
		val_len: WordSize,
	) -> Result<u32>;
	/// Delete a memory instance.
	fn memory_teardown(&mut self, memory_id: MemoryId) -> Result<()>;
	/// Create a new memory instance with the given `initial` size and the `maximum` size.
	/// The size is given in wasm pages.
	fn memory_new(&mut self, initial: u32, maximum: u32) -> Result<MemoryId>;
	/// Invoke an exported function by a name.
	fn invoke(
		&mut self,
		instance_id: u32,
		export_name: &str,
		args: &[u8],
		return_val: Pointer<u8>,
		return_val_len: WordSize,
		state: u32,
	) -> Result<u32>;
	/// Delete a sandbox instance.
	fn instance_teardown(&mut self, instance_id: u32) -> Result<()>;
	/// Create a new sandbox instance.
	fn instance_new(
		&mut self,
		dispatch_thunk_id: u32,
		wasm: &[u8],
		raw_env_def: &[u8],
		state: u32,
	) -> Result<u32>;

	/// Get the value from a global with the given `name`. The sandbox is determined by the
	/// given `instance_idx` instance.
	///
	/// Returns `Some(_)` when the requested global variable could be found.
	fn get_global_val(&self, instance_idx: u32, name: &str) -> Result<Option<Value>>;
}

/// Something that provides implementations for host functions.
pub trait HostFunctions: 'static {
	/// Returns the host functions `Self` provides.
	fn host_functions() -> Vec<&'static dyn Function>;
}

#[impl_trait_for_tuples::impl_for_tuples(30)]
impl HostFunctions for Tuple {
	fn host_functions() -> Vec<&'static dyn Function> {
		let mut host_functions = Vec::new();

		for_tuples!( #( host_functions.extend(Tuple::host_functions()); )* );

		host_functions
	}
}

/// Something that can be converted into a wasm compatible `Value`.
pub trait IntoValue {
	/// The type of the value in wasm.
	const VALUE_TYPE: ValueType;

	/// Convert `self` into a wasm `Value`.
	fn into_value(self) -> Value;
}

/// Something that can may be created from a wasm `Value`.
pub trait TryFromValue: Sized {
	/// Try to convert the given `Value` into `Self`.
	fn try_from_value(val: Value) -> Option<Self>;
}

macro_rules! impl_into_and_from_value {
	(
		$(
			$type:ty, $( < $gen:ident >, )? $value_variant:ident,
		)*
	) => {
		$(
			impl $( <$gen> )? IntoValue for $type {
				const VALUE_TYPE: ValueType = ValueType::$value_variant;
				fn into_value(self) -> Value { Value::$value_variant(self as _) }
			}

			impl $( <$gen> )? TryFromValue for $type {
				fn try_from_value(val: Value) -> Option<Self> {
					match val {
						Value::$value_variant(val) => Some(val as _),
						_ => None,
					}
				}
			}
		)*
	}
}

impl_into_and_from_value! {
	u8, I32,
	u16, I32,
	u32, I32,
	u64, I64,
	i8, I32,
	i16, I32,
	i32, I32,
	i64, I64,
}

/// Something that can write a primitive to wasm memory location.
pub trait WritePrimitive<T: PointerType> {
	/// Write the given value `t` to the given memory location `ptr`.
	fn write_primitive(&mut self, ptr: Pointer<T>, t: T) -> Result<()>;
}

impl WritePrimitive<u32> for &mut dyn FunctionContext {
	fn write_primitive(&mut self, ptr: Pointer<u32>, t: u32) -> Result<()> {
		let r = t.to_le_bytes();
		self.write_memory(ptr.cast(), &r)
	}
}

impl WritePrimitive<u64> for &mut dyn FunctionContext {
	fn write_primitive(&mut self, ptr: Pointer<u64>, t: u64) -> Result<()> {
		let r = t.to_le_bytes();
		self.write_memory(ptr.cast(), &r)
	}
}

/// Something that can read a primitive from a wasm memory location.
pub trait ReadPrimitive<T: PointerType> {
	/// Read a primitive from the given memory location `ptr`.
	fn read_primitive(&self, ptr: Pointer<T>) -> Result<T>;
}

impl ReadPrimitive<u32> for &mut dyn FunctionContext {
	fn read_primitive(&self, ptr: Pointer<u32>) -> Result<u32> {
		let mut r = [0u8; 4];
		self.read_memory_into(ptr.cast(), &mut r)?;
		Ok(u32::from_le_bytes(r))
	}
}

impl ReadPrimitive<u64> for &mut dyn FunctionContext {
	fn read_primitive(&self, ptr: Pointer<u64>) -> Result<u64> {
		let mut r = [0u8; 8];
		self.read_memory_into(ptr.cast(), &mut r)?;
		Ok(u64::from_le_bytes(r))
	}
}

/// Typed value that can be returned from a function.
///
/// Basically a `TypedValue` plus `Unit`, for functions which return nothing.
#[derive(Clone, Copy, PartialEq, codec::Encode, codec::Decode, Debug)]
pub enum ReturnValue {
	/// For returning nothing.
	Unit,
	/// For returning some concrete value.
	Value(Value),
}

impl From<Value> for ReturnValue {
	fn from(v: Value) -> ReturnValue {
		ReturnValue::Value(v)
	}
}

impl ReturnValue {
	/// Maximum number of bytes `ReturnValue` might occupy when serialized with `SCALE`.
	///
	/// Breakdown:
	///  1 byte for encoding unit/value variant
	///  1 byte for encoding value type
	///  8 bytes for encoding the biggest value types available in wasm: f64, i64.
	pub const ENCODED_MAX_SIZE: usize = 10;
}

#[cfg(test)]
mod tests {
	use super::*;
	use codec::Encode;

	#[test]
	fn pointer_offset_works() {
		let ptr = Pointer::<u32>::null();

		assert_eq!(ptr.offset(10).unwrap(), Pointer::new(40));
		assert_eq!(ptr.offset(32).unwrap(), Pointer::new(128));

		let ptr = Pointer::<u64>::null();

		assert_eq!(ptr.offset(10).unwrap(), Pointer::new(80));
		assert_eq!(ptr.offset(32).unwrap(), Pointer::new(256));
	}


	#[test]
	fn return_value_encoded_max_size() {
		let encoded = ReturnValue::Value(Value::I64(-1)).encode();
		assert_eq!(encoded.len(), ReturnValue::ENCODED_MAX_SIZE);
	}
}