only measure a variable integer once where we can (#500)

3 files changed, 20 insertions, 7 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index ee380ca6c..3b2d93166 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,7 @@
 - Improvement: Command `zen gc-status` now gives details about storage, when last GC occured, how long until next GC etc
 - Improvement: New rotating file logger that keeps on running regardless of errors to avoid spamming error reports on OOM or OOD
 - Improvement: Removed HttpCidStore (was already deprecated)
+- Improvement: Optimized cases in CompactBinary reader where we would measure a variable integer twice
 - Changed: Cache access and write log are disabled by default
 - Changed: We no longer purge out block location for missing blocks to allow testing/analisys of snapshots of server states without copying full set of data
 - Changed: Merged cache memory layer with cache disk layer to reduce memory and cpu overhead
diff --git a/src/zencore/compactbinary.cpp b/src/zencore/compactbinary.cpp
index 5b599dda3..416b49f62 100644
--- a/src/zencore/compactbinary.cpp
+++ b/src/zencore/compactbinary.cpp
@@ -1319,7 +1319,7 @@ TryMeasureCompactBinary(MemoryView View, CbFieldType& OutType, uint64_t& OutSize
 			return false;
 		}
 
-		const uint64_t NameLen	= ReadVarUInt(View.GetData(), NameLenByteCount);
+		const uint64_t NameLen	= ReadMeasuredVarUInt(View.GetData(), NameLenByteCount);
 		const uint64_t NameSize = NameLen + NameLenByteCount;
 
 		if (bDynamicSize && View.GetSize() < NameSize)
@@ -1353,7 +1353,7 @@ TryMeasureCompactBinary(MemoryView View, CbFieldType& OutType, uint64_t& OutSize
 					OutSize = Size + PayloadSizeByteCount;
 					return false;
 				}
-				const uint64_t PayloadSize = ReadVarUInt(View.GetData(), PayloadSizeByteCount);
+				const uint64_t PayloadSize = ReadMeasuredVarUInt(View.GetData(), PayloadSizeByteCount);
 				OutSize					   = Size + PayloadSize + PayloadSizeByteCount;
 			}
 			return true;
diff --git a/src/zencore/include/zencore/varint.h b/src/zencore/include/zencore/varint.h
index e57e1d497..c0d63d814 100644
--- a/src/zencore/include/zencore/varint.h
+++ b/src/zencore/include/zencore/varint.h
@@ -104,15 +104,12 @@ MeasureVarInt(int64_t InValue)
  * Read a variable-length unsigned integer.
  *
  * @param InData A variable-length encoding of an unsigned integer.
- * @param OutByteCount The number of bytes consumed from the input.
+ * @param ByteCount The number of bytes to be consumed from the input.
  * @return An unsigned integer.
  */
 inline uint64_t
-ReadVarUInt(const void* InData, uint32_t& OutByteCount)
+ReadMeasuredVarUInt(const void* InData, uint32_t ByteCount)
 {
-	const uint32_t ByteCount = MeasureVarUInt(InData);
-	OutByteCount			 = ByteCount;
-
 	const uint8_t* InBytes = static_cast<const uint8_t*>(InData);
 	uint64_t	   Value   = *InBytes++ & uint8_t(0xff >> ByteCount);
 	switch (ByteCount - 1)
@@ -155,6 +152,21 @@ ReadVarUInt(const void* InData, uint32_t& OutByteCount)
 }
 
 /**
+ * Read a variable-length unsigned integer.
+ *
+ * @param InData A variable-length encoding of an unsigned integer.
+ * @param OutByteCount The number of bytes consumed from the input.
+ * @return An unsigned integer.
+ */
+inline uint64_t
+ReadVarUInt(const void* InData, uint32_t& OutByteCount)
+{
+	const uint32_t ByteCount = MeasureVarUInt(InData);
+	OutByteCount			 = ByteCount;
+	return ReadMeasuredVarUInt(InData, ByteCount);
+}
+
+/**
  * Read a variable-length signed integer.
  *
  * @param InData A variable-length encoding of a signed integer.