Adding Bridges code as git subtree. (#2515)

* Add instructions.

* Squashed 'bridges/' content from commit 345e84a21

git-subtree-dir: bridges
git-subtree-split: 345e84a2146b56628e9888c9f5e129cb40e868a9

* Remove bridges workspace file to avoid confusing Cargo.

* Add some bridges primitives to Polkadot workspace.

* Improve docs.

polkadot/bridges/modules/currency-exchange/src/benchmarking.rs

@@ -0,0 +1,134 @@
+// Copyright 2019-2020 Parity Technologies (UK) Ltd.
+// This file is part of Parity Bridges Common.
+
+// Parity Bridges Common is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity Bridges Common is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity Bridges Common.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Exchange module complexity is mostly determined by callbacks, defined by runtime.
+//! So we are giving runtime opportunity to prepare environment and construct proof
+//! before invoking module calls.
+
+use super::{
+	Call, Config as CurrencyExchangeConfig, InclusionProofVerifier, Instance, Module as CurrencyExchangeModule,
+};
+use sp_std::prelude::*;
+
+use frame_benchmarking::{account, benchmarks_instance};
+use frame_system::RawOrigin;
+
+const SEED: u32 = 0;
+const WORST_TX_SIZE_FACTOR: u32 = 1000;
+const WORST_PROOF_SIZE_FACTOR: u32 = 1000;
+
+/// Module we're benchmarking here.
+pub struct Module<T: Config<I>, I: Instance>(CurrencyExchangeModule<T, I>);
+
+/// Proof benchmarking parameters.
+pub struct ProofParams<Recipient> {
+	/// Funds recipient.
+	pub recipient: Recipient,
+	/// When true, recipient must exists before import.
+	pub recipient_exists: bool,
+	/// When 0, transaction should have minimal possible size. When this value has non-zero value n,
+	/// transaction size should be (if possible) near to MIN_SIZE + n * SIZE_FACTOR.
+	pub transaction_size_factor: u32,
+	/// When 0, proof should have minimal possible size. When this value has non-zero value n,
+	/// proof size should be (if possible) near to MIN_SIZE + n * SIZE_FACTOR.
+	pub proof_size_factor: u32,
+}
+
+/// Config that must be implemented by runtime.
+pub trait Config<I: Instance>: CurrencyExchangeConfig<I> {
+	/// Prepare proof for importing exchange transaction.
+	fn make_proof(
+		proof_params: ProofParams<Self::AccountId>,
+	) -> <<Self as CurrencyExchangeConfig<I>>::PeerBlockchain as InclusionProofVerifier>::TransactionInclusionProof;
+}
+
+benchmarks_instance! {
+	// Benchmark `import_peer_transaction` extrinsic with the best possible conditions:
+	// * Proof is the transaction itself.
+	// * Transaction has minimal size.
+	// * Recipient account exists.
+	import_peer_transaction_best_case {
+		let i in 1..100;
+
+		let recipient: T::AccountId = account("recipient", i, SEED);
+		let proof = T::make_proof(ProofParams {
+			recipient: recipient.clone(),
+			recipient_exists: true,
+			transaction_size_factor: 0,
+			proof_size_factor: 0,
+		});
+	}: import_peer_transaction(RawOrigin::Signed(recipient), proof)
+
+	// Benchmark `import_peer_transaction` extrinsic when recipient account does not exists.
+	import_peer_transaction_when_recipient_does_not_exists {
+		let i in 1..100;
+
+		let recipient: T::AccountId = account("recipient", i, SEED);
+		let proof = T::make_proof(ProofParams {
+			recipient: recipient.clone(),
+			recipient_exists: false,
+			transaction_size_factor: 0,
+			proof_size_factor: 0,
+		});
+	}: import_peer_transaction(RawOrigin::Signed(recipient), proof)
+
+	// Benchmark `import_peer_transaction` when transaction size increases.
+	import_peer_transaction_when_transaction_size_increases {
+		let i in 1..100;
+		let n in 1..WORST_TX_SIZE_FACTOR;
+
+		let recipient: T::AccountId = account("recipient", i, SEED);
+		let proof = T::make_proof(ProofParams {
+			recipient: recipient.clone(),
+			recipient_exists: true,
+			transaction_size_factor: n,
+			proof_size_factor: 0,
+		});
+	}: import_peer_transaction(RawOrigin::Signed(recipient), proof)
+
+	// Benchmark `import_peer_transaction` when proof size increases.
+	import_peer_transaction_when_proof_size_increases {
+		let i in 1..100;
+		let n in 1..WORST_PROOF_SIZE_FACTOR;
+
+		let recipient: T::AccountId = account("recipient", i, SEED);
+		let proof = T::make_proof(ProofParams {
+			recipient: recipient.clone(),
+			recipient_exists: true,
+			transaction_size_factor: 0,
+			proof_size_factor: n,
+		});
+	}: import_peer_transaction(RawOrigin::Signed(recipient), proof)
+
+	// Benchmark `import_peer_transaction` extrinsic with the worst possible conditions:
+	// * Proof is large.
+	// * Transaction has large size.
+	// * Recipient account does not exists.
+	import_peer_transaction_worst_case {
+		let i in 1..100;
+		let m in WORST_TX_SIZE_FACTOR..WORST_TX_SIZE_FACTOR+1;
+		let n in WORST_PROOF_SIZE_FACTOR..WORST_PROOF_SIZE_FACTOR+1;
+
+		let recipient: T::AccountId = account("recipient", i, SEED);
+		let proof = T::make_proof(ProofParams {
+			recipient: recipient.clone(),
+			recipient_exists: false,
+			transaction_size_factor: m,
+			proof_size_factor: n,
+		});
+	}: import_peer_transaction(RawOrigin::Signed(recipient), proof)
+
+}