jsrrdgraph: Performance fix

commit 2a74a333ff143499b465234f0395a4aad7bdaa78 ("Upgrade to
javascriptrrd ver 1.1.1") converted getByteAt calls to a getEndianByteAt
call, but this also introduced a branch operation. Since endianess is
dependent on the file, we can move the switch_endian check outside the
function.

Performance improved from 0.148ms (n=336k) to .039ms (n=384k) which
translates to about 30 seconds!

1 files changed, 9 insertions, 6 deletions

diff --git a/js/binaryXHR.js b/js/binaryXHR.js
index 63186b3..6749273 100644
--- a/js/binaryXHR.js
+++ b/js/binaryXHR.js
@@ -63,12 +63,15 @@ function BinaryFile(strData, iDataOffset, iDataLength) {
                 throw new InvalidBinaryFile("Unsupported type " + (typeof strData));
         }
 
-        this.getEndianByteAt = function(iOffset,width,delta) {
-                if (this.switch_endian)
-                        return this.getByteAt(iOffset+width-delta-1);
-                else
-                        return this.getByteAt(iOffset+delta);
-        };
+        if (switch_endian) {
+                this.getEndianByteAt = function(iOffset, width, delta) {
+                        return this.getByteAt(iOffset + width - delta - 1);
+                };
+        } else {
+                this.getEndianByteAt = function(iOffset, width, delta) {
+                        return this.getByteAt(iOffset + delta);
+                };
+        }
 
         this.getLength = function() {
                 return dataLength;