Add WriteMeasuredVarUInt to avoid measuring ints twice before writing (#665)

Avoid double resize of buffer in CbWriter::SetName and CbWriter::AddBinary
Add WriteMeasuredVarUInt to avoid measuring ints twice before writing

1 files changed, 37 insertions, 9 deletions

diff --git a/src/zencore/include/zencore/varint.h b/src/zencore/include/zencore/varint.h
index c0d63d814..ae9aceed6 100644
--- a/src/zencore/include/zencore/varint.h
+++ b/src/zencore/include/zencore/varint.h
@@ -181,17 +181,17 @@ ReadVarInt(const void* InData, uint32_t& OutByteCount)
 }
 
 /**
- * Write a variable-length unsigned integer.
+ * Write a pre-measured variable-length unsigned integer.
  *
  * @param InValue An unsigned integer to encode.
+ * @param ByteCount The number of bytes the integer requires to be encoded
  * @param OutData A buffer of at least 5 bytes to write the output to.
  * @return The number of bytes used in the output.
  */
-inline uint32_t
-WriteVarUInt(uint32_t InValue, void* OutData)
+inline void
+WriteMeasuredVarUInt(uint32_t InValue, uint32_t ByteCount, void* OutData)
 {
-	const uint32_t ByteCount = MeasureVarUInt(InValue);
-	uint8_t*	   OutBytes	 = static_cast<uint8_t*>(OutData) + ByteCount - 1;
+	uint8_t* OutBytes = static_cast<uint8_t*>(OutData) + ByteCount - 1;
 	switch (ByteCount - 1)
 	{
 		case 4:
@@ -214,21 +214,35 @@ WriteVarUInt(uint32_t InValue, void* OutData)
 			break;
 	}
 	*OutBytes = uint8_t(0xff << (9 - ByteCount)) | uint8_t(InValue);
-	return ByteCount;
 }
 
 /**
  * Write a variable-length unsigned integer.
  *
  * @param InValue An unsigned integer to encode.
- * @param OutData A buffer of at least 9 bytes to write the output to.
+ * @param OutData A buffer of at least 5 bytes to write the output to.
  * @return The number of bytes used in the output.
  */
 inline uint32_t
-WriteVarUInt(uint64_t InValue, void* OutData)
+WriteVarUInt(uint32_t InValue, void* OutData)
 {
 	const uint32_t ByteCount = MeasureVarUInt(InValue);
-	uint8_t*	   OutBytes	 = static_cast<uint8_t*>(OutData) + ByteCount - 1;
+	WriteMeasuredVarUInt(InValue, MeasureVarUInt(InValue), OutData);
+	return ByteCount;
+}
+
+/**
+ * Write a pre-measured variable-length unsigned integer.
+ *
+ * @param InValue An unsigned integer to encode.
+ * @param ByteCount The number of bytes the integer requires to be encoded
+ * @param OutData A buffer of at least 9 bytes to write the output to.
+ * @return The number of bytes used in the output.
+ */
+inline void
+WriteMeasuredVarUInt(uint64_t InValue, uint32_t ByteCount, void* OutData)
+{
+	uint8_t* OutBytes = static_cast<uint8_t*>(OutData) + ByteCount - 1;
 	switch (ByteCount - 1)
 	{
 		case 8:
@@ -267,6 +281,20 @@ WriteVarUInt(uint64_t InValue, void* OutData)
 			break;
 	}
 	*OutBytes = uint8_t(0xff << (9 - ByteCount)) | uint8_t(InValue);
+}
+
+/**
+ * Write a variable-length unsigned integer.
+ *
+ * @param InValue An unsigned integer to encode.
+ * @param OutData A buffer of at least 9 bytes to write the output to.
+ * @return The number of bytes used in the output.
+ */
+inline uint32_t
+WriteVarUInt(uint64_t InValue, void* OutData)
+{
+	const uint32_t ByteCount = MeasureVarUInt(InValue);
+	WriteMeasuredVarUInt(InValue, ByteCount, OutData);
 	return ByteCount;
 }