Add signed support to BitStream and BitWriter

1 files changed, 17 insertions, 0 deletions

diff --git a/libqpdf/BitStream.cc b/libqpdf/BitStream.cc
index 14eae55d..bb52af31 100644
--- a/libqpdf/BitStream.cc
+++ b/libqpdf/BitStream.cc
@@ -30,6 +30,23 @@ BitStream::getBits(int nbits)
 		     this->bits_available, nbits);
 }
 
+long long
+BitStream::getBitsSigned(int nbits)
+{
+    unsigned long long bits = read_bits(this->p, this->bit_offset,
+                                        this->bits_available, nbits);
+    long long result = 0;
+    if (static_cast<long long>(bits) > 1 << (nbits - 1))
+    {
+        result = static_cast<long long>(bits - (1 << nbits));
+    }
+    else
+    {
+        result = static_cast<long long>(bits);
+    }
+    return result;
+}
+
 void
 BitStream::skipToNextByte()
 {