Storage chains: indexing, renewals and reference counting (#8265)

* Transaction indexing

* Tests and fixes

* Fixed a comment

* Style

* Build

* Style

* Apply suggestions from code review

Co-authored-by: cheme <emericchevalier.pro@gmail.com>

* Code review suggestions

* Add missing impl

* Apply suggestions from code review

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* impl JoinInput

* Don't store empty slices

* JoinInput operates on slices

Co-authored-by: cheme <emericchevalier.pro@gmail.com>
Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

substrate/client/db/src/utils.rs

@@ -278,7 +278,7 @@ pub fn open_database<Block: BlockT>(
 		#[cfg(feature = "with-parity-db")]
 		DatabaseSettingsSrc::ParityDb { path } => {
 			crate::parity_db::open(&path, db_type)
-				.map_err(|e| sp_blockchain::Error::Backend(format!("{:?}", e)))?
+				.map_err(|e| sp_blockchain::Error::Backend(format!("{}", e)))?
 		},
 		#[cfg(not(feature = "with-parity-db"))]
 		DatabaseSettingsSrc::ParityDb { .. } => {
@@ -449,10 +449,35 @@ impl DatabaseType {
 	}
 }
 
+pub(crate) struct JoinInput<'a, 'b>(&'a [u8], &'b [u8]);
+
+pub(crate) fn join_input<'a, 'b>(i1: &'a[u8], i2: &'b [u8]) -> JoinInput<'a, 'b> {
+	JoinInput(i1, i2)
+}
+
+impl<'a, 'b> codec::Input for JoinInput<'a, 'b> {
+	fn remaining_len(&mut self) -> Result<Option<usize>, codec::Error> {
+		Ok(Some(self.0.len() + self.1.len()))
+	}
+
+	fn read(&mut self, into: &mut [u8]) -> Result<(), codec::Error> {
+		let mut read = 0;
+		if self.0.len() > 0 {
+			read = std::cmp::min(self.0.len(), into.len());
+			self.0.read(&mut into[..read])?;
+		}
+		if read < into.len() {
+			self.1.read(&mut into[read..])?;
+		}
+		Ok(())
+	}
+}
+
 #[cfg(test)]
 mod tests {
 	use super::*;
 	use sp_runtime::testing::{Block as RawBlock, ExtrinsicWrapper};
+	use codec::Input;
 	type Block = RawBlock<ExtrinsicWrapper<u32>>;
 
 	#[test]
@@ -469,4 +494,25 @@ mod tests {
 		assert_eq!(DatabaseType::Full.as_str(), "full");
 		assert_eq!(DatabaseType::Light.as_str(), "light");
 	}
+
+	#[test]
+	fn join_input_works() {
+		let buf1 = [1, 2, 3, 4];
+		let buf2 = [5, 6, 7, 8];
+		let mut test = [0, 0, 0];
+		let mut joined = join_input(buf1.as_ref(), buf2.as_ref());
+		assert_eq!(joined.remaining_len().unwrap(), Some(8));
+
+		joined.read(&mut test).unwrap();
+		assert_eq!(test, [1, 2, 3]);
+		assert_eq!(joined.remaining_len().unwrap(), Some(5));
+
+		joined.read(&mut test).unwrap();
+		assert_eq!(test, [4, 5, 6]);
+		assert_eq!(joined.remaining_len().unwrap(), Some(2));
+
+		joined.read(&mut test[0..2]).unwrap();
+		assert_eq!(test, [7, 8, 6]);
+		assert_eq!(joined.remaining_len().unwrap(), Some(0));
+	}
 }