Unify checksum calculation of EAN-8 and EAN-13.

The algorithm is the same.

Change-Id: Ia5713f6b1602aafac546047b8d398048d6532686
Reviewed-on: https://pdfium-review.googlesource.com/13290
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: Henrique Nakashima <hnakashima@chromium.org>

1 files changed, 21 insertions, 0 deletions

diff --git a/fxbarcode/oned/BC_OnedEANChecksum.cpp b/fxbarcode/oned/BC_OnedEANChecksum.cpp
new file mode 100644
index 0000000000..744a60827e
--- /dev/null
+++ b/fxbarcode/oned/BC_OnedEANChecksum.cpp
@@ -0,0 +1,21 @@
+// Copyright 2017 PDFium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "fxbarcode/oned/BC_OnedEANChecksum.h"
+
+#include "core/fxcrt/fx_extension.h"
+
+int32_t EANCalcChecksum(const CFX_ByteString& contents) {
+  int32_t odd = 0;
+  int32_t even = 0;
+  FX_STRSIZE parity = 1;
+  for (FX_STRSIZE i = contents.GetLength(); i > 0; i--) {
+    if (parity % 2)
+      odd += FXSYS_DecimalCharToInt(contents[i - 1]);
+    else
+      even += FXSYS_DecimalCharToInt(contents[i - 1]);
+    parity++;
+  }
+  return (10 - (odd * 3 + even) % 10) % 10;
+}