From ed9a707f144688997618594a2d51a130e4ec6e49 Mon Sep 17 00:00:00 2001
From: Dave Hickin <david.hickin@diamond.ac.uk>
Date: Mon, 31 Aug 2015 23:50:51 +0100
Subject: [PATCH] More efficient implementation of NTTable

Cache the value field. Allows simpler implementation of getColumn().
---
 src/nt/nttable.cpp | 4 ++--
 src/nt/nttable.h   | 1 +
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/nt/nttable.cpp b/src/nt/nttable.cpp
index 5f9ab0b..1964aca 100644
--- a/src/nt/nttable.cpp
+++ b/src/nt/nttable.cpp
@@ -245,11 +245,11 @@ StringArray const & NTTable::getColumnNames() const
 
 PVFieldPtr NTTable::getColumn(std::string const & columnName) const
 {
-    return pvNTTable->getSubField("value." + columnName);
+    return pvValue->getSubField(columnName);
 }
 
 NTTable::NTTable(PVStructurePtr const & pvStructure) :
-    pvNTTable(pvStructure)
+    pvNTTable(pvStructure), pvValue(pvNTTable->getSubField<PVStructure>("value"))
 {}
 
 
diff --git a/src/nt/nttable.h b/src/nt/nttable.h
index 683ec35..0f02cc5 100644
--- a/src/nt/nttable.h
+++ b/src/nt/nttable.h
@@ -288,6 +288,7 @@ public:
 private:
     NTTable(epics::pvData::PVStructurePtr const & pvStructure);
     epics::pvData::PVStructurePtr pvNTTable;
+    epics::pvData::PVStructurePtr pvValue;
     friend class detail::NTTableBuilder;
 };