From 8c5bc7830774960e3e12c69c4ca0d58bb712d3de Mon Sep 17 00:00:00 2001
From: Rogier <rogier777@gmail.com>
Date: Tue, 10 Mar 2015 12:43:45 +0100
Subject: [PATCH] If leveldb key format is not known, try both variants

---
 db-leveldb.cpp | 41 ++++++++++++++++++++++++++++++++++++++---
 db-leveldb.h   |  2 ++
 2 files changed, 40 insertions(+), 3 deletions(-)

diff --git a/db-leveldb.cpp b/db-leveldb.cpp
index 7f78565..730ee21 100644
--- a/db-leveldb.cpp
+++ b/db-leveldb.cpp
@@ -18,7 +18,9 @@ inline std::string i64tos(int64_t i) {
 
 DBLevelDB::DBLevelDB(const std::string &mapdir) :
 	m_blocksReadCount(0),
-	m_blocksQueriedCount(0)
+	m_blocksQueriedCount(0),
+	m_keyFormatI64Usage(0),
+	m_keyFormatAXYZUsage(0)
 {
 	leveldb::Options options;
 	options.create_if_missing = false;
@@ -56,9 +58,42 @@ DB::Block DBLevelDB::getBlockOnPos(const BlockPos &pos)
 	std::string datastr;
 	leveldb::Status status;
 
-	m_blocksQueriedCount++;
 
-	status = m_db->Get(leveldb::ReadOptions(), pos.databasePosStr(), &datastr);
+	// If block format is not known, try both alternatives, but prefer
+	// the version that has worked best in recent history
+	if (pos.databaseFormat() == BlockPos::Unknown) {
+		BlockPos::StrFormat format[2];
+		if (m_keyFormatI64Usage > m_keyFormatAXYZUsage) {
+			format[0] = BlockPos::I64;
+			format[1] = BlockPos::AXYZ;
+		}
+		else {
+			format[0] = BlockPos::AXYZ;
+			format[1] = BlockPos::I64;
+		}
+		int i;
+		for (i = 0; i < 2; i++) {
+			m_blocksQueriedCount++;
+			status = m_db->Get(leveldb::ReadOptions(), pos.databasePosStrFmt(format[i]), &datastr);
+			if (status.ok())
+				break;
+		}
+		if (i < 2) {
+			if (format[i] == BlockPos::I64) {
+				m_keyFormatI64Usage = (m_keyFormatI64Usage << 1) | 0x01;
+				m_keyFormatAXYZUsage = (m_keyFormatAXYZUsage >> 1);
+			}
+			else {
+				m_keyFormatAXYZUsage = (m_keyFormatAXYZUsage << 1) | 0x01;
+				m_keyFormatI64Usage = (m_keyFormatI64Usage >> 1);
+			}
+		}
+	}
+	else {
+		m_blocksQueriedCount++;
+		status = m_db->Get(leveldb::ReadOptions(), pos.databasePosStr(), &datastr);
+	}
+
 	if(status.ok()) {
 		m_blocksReadCount++;
 		return Block(pos, ustring(reinterpret_cast<const unsigned char *>(datastr.c_str()), datastr.size()));
diff --git a/db-leveldb.h b/db-leveldb.h
index eadd219..bc2ddbb 100644
--- a/db-leveldb.h
+++ b/db-leveldb.h
@@ -18,6 +18,8 @@ private:
 	int m_blocksQueriedCount;
 	leveldb::DB *m_db;
 	BlockPosList m_blockPosList;
+	unsigned m_keyFormatI64Usage;
+	unsigned m_keyFormatAXYZUsage;
 };
 
 #endif // _DB_LEVELDB_H