fix relying on integer underflow

1 files changed, 3 insertions, 2 deletions

diff --git a/lodepng.cpp b/lodepng.cpp
index fcad93e..8c78758 100644
--- a/lodepng.cpp
+++ b/lodepng.cpp
@@ -2385,9 +2385,10 @@ static unsigned readBitsFromReversedStream(size_t* bitpointer, const unsigned ch
 {
   unsigned result = 0;
   size_t i;
-  for(i = nbits - 1; i < nbits; --i)
+  for(i = 0 ; i < nbits; ++i)
   {
-    result += (unsigned)readBitFromReversedStream(bitpointer, bitstream) << i;
+    result <<= 1;
+    result |= (unsigned)readBitFromReversedStream(bitpointer, bitstream);
   }
   return result;
 }