Improve performance of readLong function unrolling loop and using bitwise operators instead of additions

[robertonr]

Hello, I'm using mssql-jdbc driver for long time and profiling my application for 20 minutes I found that TDSChannel.read() is taking around 548297 milliseconds of CPU (I guess it's due to synchronization). However improving readLong method I reduced around 30000 milliseconds of pure CPU usage.

Could you merge this small change, please?

[codecov-io]

Codecov Report

Merging #763 into dev will increase coverage by 0.24%.
The diff coverage is 90%.

@@             Coverage Diff              @@
##                dev     #763      +/-   ##
============================================
+ Coverage     48.17%   48.41%   +0.24%     
- Complexity     2776     2799      +23     
============================================
  Files           116      116              
  Lines         27854    27852       -2     
  Branches       4636     4635       -1     
============================================
+ Hits          13418    13484      +66     
- Misses        12215    12232      +17     
+ Partials       2221     2136      -85

Flag	Coverage Δ	Complexity Δ
#JDBC42	47.54% <90%> (-0.17%)	2723 <2> (-12)
#JDBC43	48.31% <90%> (+0.3%)	2798 <2> (+29)	⬆️

Impacted Files	Coverage Δ	Complexity Δ
...in/java/com/microsoft/sqlserver/jdbc/IOBuffer.java	55.7% <0%> (+1.89%)	0 <0> (ø)	⬇️
...c/main/java/com/microsoft/sqlserver/jdbc/Util.java	60.9% <100%> (+1.08%)	90 <2> (+3)	⬆️
...rc/main/java/com/microsoft/sqlserver/jdbc/DDC.java	44.63% <0%> (-1.1%)	106% <0%> (-2%)
...ncurrentlinkedhashmap/ConcurrentLinkedHashMap.java	38.36% <0%> (-0.65%)	42% <0%> (-1%)
...rc/main/java/com/microsoft/sqlserver/jdbc/dtv.java	62.31% <0%> (-0.24%)	0% <0%> (ø)
...m/microsoft/sqlserver/jdbc/SQLServerResultSet.java	32.03% <0%> (-0.2%)	247% <0%> (-1%)
...m/microsoft/sqlserver/jdbc/SQLServerException.java	77.27% <0%> (ø)	32% <0%> (+1%)	⬆️
...om/microsoft/sqlserver/jdbc/SQLServerBulkCopy.java	52.6% <0%> (ø)	262% <0%> (ø)	⬇️
...n/java/com/microsoft/sqlserver/jdbc/DataTypes.java	79.48% <0%> (+0.19%)	5% <0%> (+1%)	⬆️
...m/microsoft/sqlserver/jdbc/SQLServerStatement.java	60.05% <0%> (+0.28%)	142% <0%> (+6%)	⬆️
... and 5 more

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[msftclas]

All CLA requirements met.

[rene-ye]

Hi @robertonr, thank you for your contribution to the mssql-jdbc driver. Please restrict the visibility of writeLong as to not introduce any new public APIs. If the concern is allowing the function to be tested, the team can do that. Other than that the changes look good.

[robertonr]

Hello, the change of visibility is done, thank you!