Simplify block marker metadata (#985)

* wip BlockMarker struct, get rid of PMMRMetadata
* use rewind to init the txhashet correctly on startup, we do not need to track pos via metadata (we have block markers), we do not need to open the txhashset with specific pos (we have rewind)
* better logging on init
* keep rewinding and validating on init, to find a good block
* use validate_roots on chain init

core/src/core/pmmr.rs

@@ -799,6 +799,10 @@ impl PruneList {
 /// side of the range, and navigates toward lower siblings toward the right
 /// of the range.
 pub fn peaks(num: u64) -> Vec<u64> {
+	if num == 0 {
+		return vec![];
+	}
+
 	// detecting an invalid mountain range, when siblings exist but no parent
 	// exists
 	if bintree_postorder_height(num + 1) > bintree_postorder_height(num) {
@@ -838,6 +842,10 @@ pub fn peaks(num: u64) -> Vec<u64> {
 /// The number of leaves nodes in a MMR of the provided size. Uses peaks to
 /// get the positions of all full binary trees and uses the height of these
 pub fn n_leaves(mut sz: u64) -> u64 {
+	if sz == 0 {
+		return 0;
+	}
+
 	while bintree_postorder_height(sz + 1) > 0 {
 		sz += 1;
 	}
@@ -1140,16 +1148,6 @@ mod test {
 		}
 	}
 
-	#[test]
-	fn test_leaf_index() {
-		assert_eq!(n_leaves(1), 1);
-		assert_eq!(n_leaves(2), 2);
-		assert_eq!(n_leaves(4), 3);
-		assert_eq!(n_leaves(5), 4);
-		assert_eq!(n_leaves(8), 5);
-		assert_eq!(n_leaves(9), 6);
-	}
-
 	#[test]
 	fn some_all_ones() {
 		for n in vec![1, 7, 255] {
@@ -1190,15 +1188,22 @@ mod test {
 		}
 	}
 
-	// Trst our n_leaves impl does the right thing for various MMR sizes
 	#[test]
-	fn various_n_leaves() {
+	fn test_n_leaves() {
+		// make sure we handle an empty MMR correctly
+		assert_eq!(n_leaves(0), 0);
+
+		// and various sizes on non-empty MMRs
 		assert_eq!(n_leaves(1), 1);
-		// 2 is not a valid size for a tree, but n_leaves rounds up to next valid tree
-		// size
 		assert_eq!(n_leaves(2), 2);
 		assert_eq!(n_leaves(3), 2);
+		assert_eq!(n_leaves(4), 3);
+		assert_eq!(n_leaves(5), 4);
+		assert_eq!(n_leaves(6), 4);
 		assert_eq!(n_leaves(7), 4);
+		assert_eq!(n_leaves(8), 5);
+		assert_eq!(n_leaves(9), 6);
+		assert_eq!(n_leaves(10), 6);
 	}
 
 	/// Find parent and sibling positions for various node positions.
@@ -1281,7 +1286,13 @@ mod test {
 	#[test]
 	fn some_peaks() {
 		// 0 0 1 0 0 1 2 0 0 1 0 0 1 2 3
+
 		let empty: Vec<u64> = vec![];
+
+		// make sure we handle an empty MMR correctly
+		assert_eq!(peaks(0), empty);
+
+		// and various non-empty MMRs
 		assert_eq!(peaks(1), [1]);
 		assert_eq!(peaks(2), empty);
 		assert_eq!(peaks(3), [3]);
@@ -1921,19 +1932,6 @@ mod test {
 		// assert_eq!(pl.get_shift(17), Some(11));
 	}
 
-	#[test]
-	fn n_size_check() {
-		assert_eq!(n_leaves(1), 1);
-		assert_eq!(n_leaves(2), 2);
-		assert_eq!(n_leaves(3), 2);
-		assert_eq!(n_leaves(4), 3);
-		assert_eq!(n_leaves(5), 4);
-		assert_eq!(n_leaves(7), 4);
-		assert_eq!(n_leaves(8), 5);
-		assert_eq!(n_leaves(9), 6);
-		assert_eq!(n_leaves(10), 6);
-	}
-
 	#[test]
 	fn check_all_ones() {
 		for i in 0..1000000 {