triedb/pathdb: implement iterator of history index (#32981)

This change introduces an iterator for the history index in the pathdb.
It provides sequential access to historical entries, enabling efficient 
scanning and future features built on top of historical state traversal.

Author: rjl493456442

triedb/pathdb/history_index.go

@@ -20,7 +20,6 @@ import (
 	"errors"
 	"fmt"
 	"math"
-	"sort"
 
 	"github.com/ethereum/go-ethereum/core/rawdb"
 	"github.com/ethereum/go-ethereum/ethdb"
@@ -119,30 +118,34 @@ func (r *indexReader) refresh() error {
 	return nil
 }
 
+// newIterator creates an iterator for traversing the index entries.
+func (r *indexReader) newIterator() *indexIterator {
+	return newIndexIterator(r.descList, func(id uint32) (*blockReader, error) {
+		br, ok := r.readers[id]
+		if !ok {
+			var err error
+			br, err = newBlockReader(readStateIndexBlock(r.state, r.db, id))
+			if err != nil {
+				return nil, err
+			}
+			r.readers[id] = br
+		}
+		return br, nil
+	})
+}
+
 // readGreaterThan locates the first element that is greater than the specified
 // id. If no such element is found, MaxUint64 is returned.
 func (r *indexReader) readGreaterThan(id uint64) (uint64, error) {
-	index := sort.Search(len(r.descList), func(i int) bool {
-		return id < r.descList[i].max
-	})
-	if index == len(r.descList) {
-		return math.MaxUint64, nil
+	it := r.newIterator()
+	found := it.SeekGT(id)
+	if err := it.Error(); err != nil {
+		return 0, err
 	}
-	desc := r.descList[index]
-
-	br, ok := r.readers[desc.id]
-	if !ok {
-		var err error
-		blob := readStateIndexBlock(r.state, r.db, desc.id)
-		br, err = newBlockReader(blob)
-		if err != nil {
-			return 0, err
-		}
-		r.readers[desc.id] = br
+	if !found {
+		return math.MaxUint64, nil
 	}
-	// The supplied ID is not greater than block.max, ensuring that an element
-	// satisfying the condition can be found.
-	return br.readGreaterThan(id)
+	return it.ID(), nil
 }
 
 // indexWriter is responsible for writing index data for a specific state (either

triedb/pathdb/history_index_block.go

@@ -21,7 +21,6 @@ import (
 	"errors"
 	"fmt"
 	"math"
-	"sort"
 )
 
 const (
@@ -164,58 +163,15 @@ func newBlockReader(blob []byte) (*blockReader, error) {
 // readGreaterThan locates the first element in the block that is greater than
 // the specified value. If no such element is found, MaxUint64 is returned.
 func (br *blockReader) readGreaterThan(id uint64) (uint64, error) {
-	var err error
-	index := sort.Search(len(br.restarts), func(i int) bool {
-		item, n := binary.Uvarint(br.data[br.restarts[i]:])
-		if n <= 0 {
-			err = fmt.Errorf("failed to decode item at restart %d", br.restarts[i])
-		}
-		return item > id
-	})
-	if err != nil {
+	it := newBlockIterator(br.data, br.restarts)
+	found := it.SeekGT(id)
+	if err := it.Error(); err != nil {
 		return 0, err
 	}
-	if index == 0 {
-		item, _ := binary.Uvarint(br.data[br.restarts[0]:])
-		return item, nil
-	}
-	var (
-		start  int
-		limit  int
-		result uint64
-	)
-	if index == len(br.restarts) {
-		// The element being searched falls within the last restart section,
-		// there is no guarantee such element can be found.
-		start = int(br.restarts[len(br.restarts)-1])
-		limit = len(br.data)
-	} else {
-		// The element being searched falls within the non-last restart section,
-		// such element can be found for sure.
-		start = int(br.restarts[index-1])
-		limit = int(br.restarts[index])
-	}
-	pos := start
-	for pos < limit {
-		x, n := binary.Uvarint(br.data[pos:])
-		if pos == start {
-			result = x
-		} else {
-			result += x
-		}
-		if result > id {
-			return result, nil
-		}
-		pos += n
-	}
-	// The element which is greater than specified id is not found.
-	if index == len(br.restarts) {
+	if !found {
 		return math.MaxUint64, nil
 	}
-	// The element which is the first one greater than the specified id
-	// is exactly the one located at the restart point.
-	item, _ := binary.Uvarint(br.data[br.restarts[index]:])
-	return item, nil
+	return it.ID(), nil
 }
 
 type blockWriter struct {