Contracts: Translate .wat fixtures to rust (#2654)

- Translate all pallet-contracts fixtures from `wat` to Rust files.
- Fix read_sandbox_memory_as to not use MaxEncodedLen as this could
break if used with types with a non-fixed encoded len.

---------

Co-authored-by: alvicsam <alvicsam@gmail.com>
Co-authored-by: Alexander Samusev <41779041+alvicsam@users.noreply.github.com>
Co-authored-by: Alexander Theißen <alex.theissen@me.com>
Co-authored-by: command-bot <>

substrate/frame/contracts/fixtures/contracts/common/Cargo.toml

@@ -6,3 +6,6 @@ authors.workspace = true
 edition.workspace = true
 license.workspace = true
 description = "Common utilities for pallet-contracts-fixtures."
+
+[dependencies]
+uapi = { package = 'pallet-contracts-uapi', path = "../../../uapi", default-features = false }

substrate/frame/contracts/fixtures/contracts/common/src/lib.rs

@@ -15,7 +15,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 #![no_std]
-#![cfg(any(target_arch = "wasm32", target_arch = "riscv32"))]
+
+pub use uapi::{HostFn, HostFnImpl as api};
 
 #[panic_handler]
 fn panic(_info: &core::panic::PanicInfo) -> ! {
@@ -29,3 +30,122 @@ fn panic(_info: &core::panic::PanicInfo) -> ! {
 		core::hint::unreachable_unchecked();
 	}
 }
+
+/// Utility macro to read input passed to a contract.
+///
+/// Example:
+///
+/// ```
+/// input$!(
+/// 		var1: u32,      // [0, 4)   var1 decoded as u32
+/// 		var2: [u8; 32], // [4, 36)  var2 decoded as a [u8] slice
+/// 		var3: u8,       // [36, 37) var3 decoded as a u8
+/// );
+///
+/// // Input and size can be specified as well:
+/// input$!(
+/// 		input,      // input buffer (optional)
+/// 		512,        // input size (optional)
+/// 		var4: u32,  // [0, 4)  var4 decoded as u32
+/// 		var5: [u8], // [4, ..) var5 decoded as a [u8] slice
+/// );
+/// ```
+#[macro_export]
+macro_rules! input {
+	(@inner $input:expr, $cursor:expr,) => {};
+	(@size $size:expr, ) => { $size };
+
+	// Match a u8 variable.
+	// e.g input!(var1: u8, );
+	(@inner $input:expr, $cursor:expr, $var:ident: u8, $($rest:tt)*) => {
+		let $var = $input[$cursor];
+		input!(@inner $input, $cursor + 1, $($rest)*);
+	};
+
+	// Size of u8 variable.
+	(@size $size:expr, $var:ident: u8, $($rest:tt)*) => {
+		input!(@size $size + 1, $($rest)*)
+	};
+
+	// Match a u64 variable.
+	// e.g input!(var1: u64, );
+	(@inner $input:expr, $cursor:expr, $var:ident: u64, $($rest:tt)*) => {
+		let $var = u64::from_le_bytes($input[$cursor..$cursor + 8].try_into().unwrap());
+		input!(@inner $input, $cursor + 8, $($rest)*);
+	};
+
+	// Size of u64 variable.
+	(@size $size:expr, $var:ident: u64, $($rest:tt)*) => {
+		input!(@size $size + 8, $($rest)*)
+	};
+
+	// Match a u32 variable.
+	// e.g input!(var1: u32, );
+	(@inner $input:expr, $cursor:expr, $var:ident: u32, $($rest:tt)*) => {
+		let $var = u32::from_le_bytes($input[$cursor..$cursor + 4].try_into().unwrap());
+		input!(@inner $input, $cursor + 4, $($rest)*);
+	};
+
+	// Size of u32 variable.
+	(@size $size:expr, $var:ident: u32, $($rest:tt)*) => {
+		input!(@size $size + 4, $($rest)*)
+	};
+
+	// Match a u8 slice with the remaining bytes.
+	// e.g input!(512, var1: [u8; 32], var2: [u8], );
+	(@inner $input:expr, $cursor:expr, $var:ident: [u8],) => {
+		let $var = &$input[$cursor..];
+	};
+
+	// Match a u8 slice of the given size.
+	// e.g input!(var1: [u8; 32], );
+	(@inner $input:expr, $cursor:expr, $var:ident: [u8; $n:expr], $($rest:tt)*) => {
+		let $var = &$input[$cursor..$cursor+$n];
+		input!(@inner $input, $cursor + $n, $($rest)*);
+	};
+
+	// Size of a u8 slice.
+	(@size $size:expr, $var:ident: [u8; $n:expr], $($rest:tt)*) => {
+		input!(@size $size + $n, $($rest)*)
+	};
+
+	// Entry point, with the buffer and it's size specified first.
+	// e.g input!(buffer, 512, var1: u32, var2: [u8], );
+	($buffer:ident, $size:expr, $($rest:tt)*) => {
+		let mut $buffer = [0u8; $size];
+		let $buffer = &mut &mut $buffer[..];
+		$crate::api::input($buffer);
+		input!(@inner $buffer, 0, $($rest)*);
+	};
+
+	// Entry point, with the name of the buffer specified and size of the input buffer computed.
+	// e.g input!(buffer, var1: u32, var2: u64, );
+	($buffer: ident, $($rest:tt)*) => {
+		input!($buffer, input!(@size 0, $($rest)*), $($rest)*);
+	};
+
+	// Entry point, with the size of the input buffer computed.
+	// e.g input!(var1: u32, var2: u64, );
+	($($rest:tt)*) => {
+		input!(buffer, $($rest)*);
+	};
+}
+
+/// Utility macro to invoke a host function that expect a `output: &mut &mut [u8]` as last argument.
+///
+/// Example:
+/// ```
+/// // call `api::caller` and store the output in `caller`
+/// output!(caller, [0u8; 32], api::caller,);
+///
+/// // call `api::get_storage` and store the output in `address`
+/// output!(address, [0u8; 32], api::get_storage, &[1u8; 32]);
+/// ```
+#[macro_export]
+macro_rules! output {
+	($output: ident, $buffer: expr, $host_fn:path, $($arg:expr),*) => {
+		let mut $output = $buffer;
+		let $output = &mut &mut $output[..];
+		$host_fn($($arg,)* $output);
+	};
+}