1 files changed, 93 insertions, 0 deletions
diff --git a/common/DSUtilLite/ByteParser.cpp b/common/DSUtilLite/ByteParser.cpp
new file mode 100644
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--- /dev/null
+++ b/common/DSUtilLite/ByteParser.cpp
@@ -0,0 +1,93 @@
+/*
+ *      Copyright (C) 2011 Hendrik Leppkes
+ *      http://www.1f0.de
+ *
+ *  This Program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2, or (at your option)
+ *  any later version.
+ *
+ *  This Program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; see the file COPYING.  If not, write to
+ *  the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+ *  http://www.gnu.org/copyleft/gpl.html
+ *
+ *  Initial design and concept by Gabest and the MPC-HC Team, copyright under GPLv2
+ */
+
+#include "stdafx.h"
+#include "ByteParser.h"
+
+CByteParser::CByteParser(const BYTE *pData, uint32_t length)
+  : m_pData(pData), m_pCurrent(pData), m_pEnd(pData+length), m_dwLen(length), m_bitBuffer(0), m_bitLen(0)
+{
+}
+
+CByteParser::~CByteParser()
+{
+}
+
+uint32_t CByteParser::BitRead(uint8_t numBits, bool peek)
+{
+  ASSERT(numBits <= 32);
+  ASSERT(numBits <= (m_bitLen + (8 * (m_pEnd - m_pCurrent))));
+
+  if (numBits == 0) { return 0; }
+
+  bool atEnd = false;
+  // Read more data in the buffer
+  while(m_bitLen < numBits) {
+    m_bitBuffer <<= 8;
+    m_bitBuffer += !atEnd ? *m_pCurrent : 0;
+    // Just a safety check so we don't cross the array boundary
+    if (m_pCurrent < m_pEnd) { m_pCurrent++; } else { atEnd = true; }
+    m_bitLen += 8;
+  }
+
+  // Number of superfluous bits in the buffer
+  int bitlen = m_bitLen - numBits;
+
+  // Compose the return value
+  // Shift the value so the superfluous bits fall off, and then crop the result with an AND
+  uint32_t ret = (m_bitBuffer >> bitlen) & ((1ui64 << numBits) - 1);
+
+  // If we're not peeking, then update the buffer and remove the data we just read
+  if(!peek) {
+    m_bitBuffer &= ((1ui64 << bitlen) - 1);
+    m_bitLen = bitlen;
+  }
+
+  return ret;
+}
+
+// Exponential Golomb Coding (with k = 0)
+// As used in H.264/MPEG-4 AVC
+// http://en.wikipedia.org/wiki/Exponential-Golomb_coding
+
+uint64_t CByteParser::UExpGolombRead() {
+  int n = -1;
+  for(BYTE b = 0; !b; n++) {
+    b = BitRead(1);
+  }
+  return (1ui64 << n) - 1 + BitRead(n);
+}
+
+int64_t CByteParser::SExpGolombRead() {
+  uint64_t k = UExpGolombRead();
+  // Negative numbers are interleaved in the series
+  // k:      0, 1,  2, 3,  4, 5,  6, ...
+  // Actual: 0, 1, -1, 2, -2, 3, -3, ....
+  // So all even numbers are negative (last bit = 0)
+  return ((k&1) ? 1 : -1) * ((k + 1) >> 1);
+}
+
+void CByteParser::Seek(DWORD pos)
+{
+  m_pCurrent = m_pData + min(m_dwLen, pos);
+  BitFlush();
+}