diff options
| -rw-r--r-- | bitreader.cc | 23 | ||||
| -rw-r--r-- | bitreader.h | 2 | ||||
| -rw-r--r-- | stfreader.cc | 4 |
3 files changed, 27 insertions, 2 deletions
diff --git a/bitreader.cc b/bitreader.cc index dc92223..8b78bb7 100644 --- a/bitreader.cc +++ b/bitreader.cc @@ -18,6 +18,17 @@ #include "bitreader.h" +namespace +{ +inline qint64 signExtend(quint64 x, int n) +{ + if (n < 64 && (x & (1 << (n-1)))) { + x |= -(1LL << n); + } + return x; +} +} + BitReader::BitReader(QIODevice *device) : child(device), buf(0), avail(0) { @@ -38,6 +49,12 @@ quint64 BitReader::readBits(int n) return x; } +qint64 BitReader::readSignedBits(int n) +{ + quint64 x = readBits(n); + return signExtend(x, n); +} + quint64 BitReader::peekBits(int n) { while (n > avail) { @@ -51,6 +68,12 @@ quint64 BitReader::peekBits(int n) return x; } +qint64 BitReader::peekSignedBits(int n) +{ + quint64 x = peekBits(n); + return signExtend(x, n); +} + void BitReader::skipUntilNextByte() { int skip = avail % 8; diff --git a/bitreader.h b/bitreader.h index c5ebf3f..327bc04 100644 --- a/bitreader.h +++ b/bitreader.h @@ -28,7 +28,9 @@ public: ~BitReader(); quint64 readBits(int n); + qint64 readSignedBits(int n); quint64 peekBits(int n); + qint64 peekSignedBits(int n); void skipUntilNextByte(); diff --git a/stfreader.cc b/stfreader.cc index 7d78635..09967cc 100644 --- a/stfreader.cc +++ b/stfreader.cc @@ -130,8 +130,8 @@ bool StfReader::parseV1(BitReader& br) pa = p1 - p0; } else { do_delta = true; - delta.setX(br.readBits(8)); - delta.setY(br.readBits(8)); + delta.setX(br.readSignedBits(8)); + delta.setY(br.readSignedBits(8)); } } else { do_delta = true; |