PMMRable cleanup (#1910)

* cleanup pmmrable and len()
introduce FixedLength trait with a const LEN
make Hash impl FixedLength for consistency

* rustfmt

* store tests cleanup

* rustfmt

* whats going on with those comments and rustfmt?

store/src/pmmr.rs

@@ -20,7 +20,7 @@ use croaring::Bitmap;
 use core::core::hash::{Hash, Hashed};
 use core::core::pmmr::{self, family, Backend, HashOnlyBackend};
 use core::core::BlockHeader;
-use core::ser::{self, PMMRable};
+use core::ser::{self, FixedLength, PMMRable};
 use leaf_set::LeafSet;
 use prune_list::PruneList;
 use types::{prune_noop, AppendOnlyFile, HashFile};
@@ -49,10 +49,7 @@ pub const PMMR_FILES: [&str; 4] = [
 /// * A leaf_set tracks unpruned (unremoved) leaf positions in the MMR..
 /// * A prune_list tracks the positions of pruned (and compacted) roots in the
 /// MMR.
-pub struct PMMRBackend<T>
-where
-	T: PMMRable,
-{
+pub struct PMMRBackend<T: PMMRable> {
 	data_dir: String,
 	prunable: bool,
 	hash_file: AppendOnlyFile,
@@ -62,16 +59,13 @@ where
 	_marker: marker::PhantomData<T>,
 }
 
-impl<T> Backend<T> for PMMRBackend<T>
-where
-	T: PMMRable + ::std::fmt::Debug,
-{
+impl<T: PMMRable> Backend<T> for PMMRBackend<T> {
 	/// Append the provided data and hashes to the backend storage.
 	/// Add the new leaf pos to our leaf_set if this is a prunable MMR.
 	#[allow(unused_variables)]
 	fn append(&mut self, data: T, hashes: Vec<Hash>) -> Result<(), String> {
 		if self.prunable {
-			let record_len = Hash::SIZE as u64;
+			let record_len = Hash::LEN as u64;
 			let shift = self.prune_list.get_total_shift();
 			let position = (self.hash_file.size_unsync() / record_len) + shift + 1;
 			self.leaf_set.add(position);
@@ -95,7 +89,7 @@ where
 		let pos = position - 1;
 
 		// Must be on disk, doing a read at the correct position
-		let hash_record_len = Hash::SIZE;
+		let hash_record_len = Hash::LEN;
 		let file_offset = ((pos - shift) as usize) * hash_record_len;
 		let data = self.hash_file.read(file_offset, hash_record_len);
 		match ser::deserialize(&mut &data[..]) {
@@ -118,7 +112,7 @@ where
 		let pos = pmmr::n_leaves(position) - 1;
 
 		// Must be on disk, doing a read at the correct position
-		let record_len = T::len();
+		let record_len = T::LEN;
 		let file_offset = ((pos - shift) as usize) * record_len;
 		let data = self.data_file.read(file_offset, record_len);
 		match ser::deserialize(&mut &data[..]) {
@@ -164,14 +158,14 @@ where
 
 		// Rewind the hash file accounting for pruned/compacted pos
 		let shift = self.prune_list.get_shift(position);
-		let record_len = Hash::SIZE as u64;
+		let record_len = Hash::LEN as u64;
 		let file_pos = (position - shift) * record_len;
 		self.hash_file.rewind(file_pos);
 
 		// Rewind the data file accounting for pruned/compacted pos
 		let leaf_shift = self.prune_list.get_leaf_shift(position);
 		let flatfile_pos = pmmr::n_leaves(position);
-		let record_len = T::len() as u64;
+		let record_len = T::LEN as u64;
 		let file_pos = (flatfile_pos - leaf_shift) * record_len;
 		self.data_file.rewind(file_pos);
 
@@ -209,10 +203,7 @@ where
 	}
 }
 
-impl<T> PMMRBackend<T>
-where
-	T: PMMRable + ::std::fmt::Debug,
-{
+impl<T: PMMRable> PMMRBackend<T> {
 	/// Instantiates a new PMMR backend.
 	/// Use the provided dir to store its files.
 	pub fn new(
@@ -263,7 +254,7 @@ where
 	pub fn unpruned_size(&self) -> io::Result<u64> {
 		let total_shift = self.prune_list.get_total_shift();
 
-		let record_len = Hash::SIZE as u64;
+		let record_len = Hash::LEN as u64;
 		let sz = self.hash_file.size()?;
 		Ok(sz / record_len + total_shift)
 	}
@@ -271,14 +262,14 @@ where
 	/// Number of elements in the underlying stored data. Extremely dependent on
 	/// pruning and compaction.
 	pub fn data_size(&self) -> io::Result<u64> {
-		let record_len = T::len() as u64;
+		let record_len = T::LEN as u64;
 		self.data_file.size().map(|sz| sz / record_len)
 	}
 
 	/// Size of the underlying hashed data. Extremely dependent on pruning
 	/// and compaction.
 	pub fn hash_size(&self) -> io::Result<u64> {
-		self.hash_file.size().map(|sz| sz / Hash::SIZE as u64)
+		self.hash_file.size().map(|sz| sz / Hash::LEN as u64)
 	}
 
 	/// Syncs all files to disk. A call to sync is required to ensure all the
@@ -348,7 +339,7 @@ where
 
 		// 1. Save compact copy of the hash file, skipping removed data.
 		{
-			let record_len = Hash::SIZE as u64;
+			let record_len = Hash::LEN as u64;
 
 			let off_to_rm = map_vec!(pos_to_rm, |pos| {
 				let shift = self.prune_list.get_shift(pos.into());
@@ -365,7 +356,7 @@ where
 
 		// 2. Save compact copy of the data file, skipping removed leaves.
 		{
-			let record_len = T::len() as u64;
+			let record_len = T::LEN as u64;
 
 			let leaf_pos_to_rm = pos_to_rm
 				.iter()
@@ -488,7 +479,7 @@ impl HashOnlyMMRBackend {
 	/// The unpruned size of this MMR backend.
 	pub fn unpruned_size(&self) -> io::Result<u64> {
 		let sz = self.hash_file.size()?;
-		Ok(sz / Hash::SIZE as u64)
+		Ok(sz / Hash::LEN as u64)
 	}
 
 	/// Discard any pending changes to this MMR backend.

store/src/types.rs

@@ -26,7 +26,7 @@ use libc::{ftruncate as ftruncate64, off_t as off64_t};
 use libc::{ftruncate64, off64_t};
 
 use core::core::hash::Hash;
-use core::ser;
+use core::ser::{self, FixedLength};
 
 /// A no-op function for doing nothing with some pruned data.
 pub fn prune_noop(_pruned_data: &[u8]) {}
@@ -58,8 +58,8 @@ impl HashFile {
 		let pos = position - 1;
 
 		// Must be on disk, doing a read at the correct position
-		let file_offset = (pos as usize) * Hash::SIZE;
-		let data = self.file.read(file_offset, Hash::SIZE);
+		let file_offset = (pos as usize) * Hash::LEN;
+		let data = self.file.read(file_offset, Hash::LEN);
 		match ser::deserialize(&mut &data[..]) {
 			Ok(h) => Some(h),
 			Err(e) => {
@@ -74,7 +74,7 @@ impl HashFile {
 
 	/// Rewind the backend file to the specified position.
 	pub fn rewind(&mut self, position: u64) -> io::Result<()> {
-		self.file.rewind(position * Hash::SIZE as u64);
+		self.file.rewind(position * Hash::LEN as u64);
 		Ok(())
 	}