alphastream variable now fits Excel max cols

2 files changed, 11 insertions, 2 deletions

diff --git a/reader/reader.go b/reader/reader.go
index b5d088b..c49bd5a 100644
--- a/reader/reader.go
+++ b/reader/reader.go
@@ -12,6 +12,9 @@ import (
 	"github.com/tealeg/xlsx"
 )
 
+const maxCols = 16384
+const maxAlphabets = (maxCols / 26) - 1
+
 //DatamapLine - a line from the datamap.
 type DatamapLine struct {
 	Key     string
@@ -84,10 +87,10 @@ func alphaSingle() []string {
 	return letters
 }
 
-var alphaStream = alphas(10)
+var alphaStream = alphas(maxAlphabets)
 
 //alphas generates the alpha column compont of Excel cell references
-//Combines n alphabets to do this.
+//Adds n alphabets to the first (A..Z) alphabet.
 func alphas(n int) []string {
 	single := alphaSingle()
 	slen := len(single)
diff --git a/reader/reader_test.go b/reader/reader_test.go
index 109b605..ff9a55c 100644
--- a/reader/reader_test.go
+++ b/reader/reader_test.go
@@ -1,6 +1,7 @@
 package reader
 
 import (
+	"log"
 	"testing"
 )
 
@@ -46,6 +47,11 @@ func TestAlphaStream(t *testing.T) {
 	if alphaStream[26] != "AA" {
 		t.Errorf("Expected AA, got %v", alphaStream[26])
 	}
+	if len(alphaStream) > maxCols {
+		t.Errorf(`Number of columns in alphastream exceeds Excel maximum.
+		alphastream contains %d, maxCols is %d`, len(alphaStream), maxCols)
+	}
+	log.Printf("Length of alphastream: %d", len(alphaStream))
 }
 
 func TestAlphaSingle(t *testing.T) {