1 files changed, 8 insertions, 2 deletions
diff --git a/fxbarcode/datamatrix/BC_C40Encoder.cpp b/fxbarcode/datamatrix/BC_C40Encoder.cpp
index e994774c4d..8edd9eccfe 100644
--- a/fxbarcode/datamatrix/BC_C40Encoder.cpp
+++ b/fxbarcode/datamatrix/BC_C40Encoder.cpp
@@ -189,8 +189,14 @@ int32_t CBC_C40Encoder::encodeChar(wchar_t c, CFX_WideString& sb, int32_t& e) {
 int32_t CBC_C40Encoder::BacktrackOneCharacter(CBC_EncoderContext* context,
                                               CFX_WideString* buffer,
                                               int32_t lastCharSize) {
+  if (context->m_pos < 1)
+    return -1;
+
   int32_t count = buffer->GetLength();
-  buffer->Delete(count - lastCharSize, count);
+  if (count < lastCharSize)
+    return -1;
+
+  buffer->Delete(count - lastCharSize, lastCharSize);
   context->m_pos--;
   wchar_t c = context->getCurrentChar();
   int32_t e = BCExceptionNO;
@@ -199,7 +205,7 @@ int32_t CBC_C40Encoder::BacktrackOneCharacter(CBC_EncoderContext* context,
   if (e != BCExceptionNO)
     return -1;
 
-  assert(len > 0);
+  ASSERT(len > 0);
   context->resetSymbolInfo();
   return len;
 }