les: expose getCheckpoint API

internal/web3ext/web3ext.go

@@ -636,12 +636,19 @@ web3._extend({
 const LES_JS = `
 web3._extend({
 	property: 'les',
-	methods: [],
+	methods: 
+	[
+		new web3._extend.Method({
+			name: 'getCheckpoint',
+			call: 'les_getCheckpoint',
+			params: 1
+		}),
+	],
 	properties: 
 	[
 		new web3._extend.Property({
-			name: 'checkpoint',
+			name: 'latestCheckpoint',
-			getter: 'les_checkpoint'
+			getter: 'les_latestCheckpoint'
 		}),
 	]
 });

les/api.go

@@ -48,9 +48,9 @@ func NewPublicLesServerAPI(server *LesServer) *PublicLesServerAPI {
 //   result[1], 32 bytes hex encoded latest section head hash
 //   result[2], 32 bytes hex encoded latest section canonical hash trie root hash
 //   result[3], 32 bytes hex encoded latest section bloom trie root hash
-func (api *PublicLesServerAPI) Checkpoint() ([4]string, error) {
+func (api *PublicLesServerAPI) LatestCheckpoint() ([4]string, error) {
 	var res [4]string
-	sectionIdx, sectionHead, chtRoot, bloomTrieRoot := api.server.getCheckpoint()
+	sectionIdx, sectionHead, chtRoot, bloomTrieRoot := api.server.latestCheckpoint()
 	if sectionHead == (common.Hash{}) || chtRoot == (common.Hash{}) || bloomTrieRoot == (common.Hash{}) {
 		return res, errNoStableCheckpoint
 	}
@@ -58,3 +58,19 @@ func (api *PublicLesServerAPI) Checkpoint() ([4]string, error) {
 	res[1], res[2], res[3] = sectionHead.Hex(), chtRoot.Hex(), bloomTrieRoot.Hex()
 	return res, nil
 }
+
+// GetCheckpoint returns the specific checkpoint package.
+//
+// The checkpoint package consists of 3 strings:
+//   result[0], 32 bytes hex encoded latest section head hash
+//   result[1], 32 bytes hex encoded latest section canonical hash trie root hash
+//   result[2], 32 bytes hex encoded latest section bloom trie root hash
+func (api *PublicLesServerAPI) GetCheckpoint(index uint64) ([3]string, error) {
+	var res [3]string
+	sectionHead, chtRoot, bloomTrieRoot := api.server.getCheckpoint(index)
+	if sectionHead == (common.Hash{}) || chtRoot == (common.Hash{}) || bloomTrieRoot == (common.Hash{}) {
+		return res, errNoStableCheckpoint
+	}
+	res[0], res[1], res[2] = sectionHead.Hex(), chtRoot.Hex(), bloomTrieRoot.Hex()
+	return res, nil
+}

les/server.go

@@ -169,14 +169,14 @@ func (s *LesServer) APIs() []rpc.API {
 	}
 }
 
-// getCheckpoint finds the common stored section index and returns a set of
+// latestCheckpoint finds the common stored section index and returns a set of
 // post-processed trie roots (CHT and BloomTrie) associated with
 // the appropriate section index and head hash as a checkpoint package.
 //
 // Note for cht, the section size in LES1 is 4K, so indexer still uses LES/1
 // 4k section size for backwards server compatibility. For bloomTrie, the size
 // of the section used for indexer is 32K.
-func (s *LesServer) getCheckpoint() (uint64, common.Hash, common.Hash, common.Hash) {
+func (s *LesServer) latestCheckpoint() (uint64, common.Hash, common.Hash, common.Hash) {
 	chtCount, _, _ := s.chtIndexer.Sections()
 	bloomTrieCount, _, _ := s.bloomTrieIndexer.Sections()
 	count := chtCount / (light.CHTFrequencyClient / light.CHTFrequencyServer)
@@ -188,13 +188,20 @@ func (s *LesServer) getCheckpoint() (uint64, common.Hash, common.Hash, common.Ha
 		// No checkpoint information can be provided.
 		return 0, common.Hash{}, common.Hash{}, common.Hash{}
 	}
+	sectionHead, chtRoot, bloomTrieRoot := s.getCheckpoint(count - 1)
+	return count - 1, sectionHead, chtRoot, bloomTrieRoot
+}
+
+// getCheckpoint returns a set of post-processed trie roots (CHT and BloomTrie)
+// associated with the appropriate head hash by specific section index.
+func (s *LesServer) getCheckpoint(index uint64) (common.Hash, common.Hash, common.Hash) {
 	// convert last LES/2 section index back to LES/1 index for chtIndexer.SectionHead
-	latest := count*(light.CHTFrequencyClient/light.CHTFrequencyServer) - 1
+	latest := (index+1)*(light.CHTFrequencyClient/light.CHTFrequencyServer) - 1
 
 	sectionHead := s.chtIndexer.SectionHead(latest)
 	chtRoot := light.GetChtRoot(s.protocolManager.chainDb, latest, sectionHead)
-	bloomTrieRoot := light.GetBloomTrieRoot(s.protocolManager.chainDb, count-1, sectionHead)
+	bloomTrieRoot := light.GetBloomTrieRoot(s.protocolManager.chainDb, index, sectionHead)
-	return count - 1, sectionHead, chtRoot, bloomTrieRoot
+	return sectionHead, chtRoot, bloomTrieRoot
 }
 
 // checkpointLoop starts a standalone goroutine to watch new checkpoint event and updates local's stable checkpoint.