1 files changed, 158 insertions, 0 deletions
diff --git a/cursor.cpp b/cursor.cpp
new file mode 100755
index 0000000..cef8c7a
--- /dev/null
+++ b/cursor.cpp
@@ -0,0 +1,158 @@
+/* $Id: cursor.cpp,v 1.3 2006/11/05 04:42:43 ganzhorn Exp $
+ * This file is part of lfhex.
+ * Copyright (C) 2006 Salem Ganzhorn <eyekode@yahoo.com>
+ *
+ * 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 version 2.
+ *
+ * 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; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ */
+
+#include "local.h"
+#include "cursor.hpp"
+
+//
+// Cursor implimentation
+//
+
+Cursor::Cursor(off_t byteOffset, 
+	       off_t charOffset, 
+	       off_t low,
+	       off_t high,
+	       off_t charsPerByte) 
+: _byteOffset(byteOffset), 
+  _charOffset(charOffset), 
+  _low(low),
+  _high(high),
+  _charsPerByte(charsPerByte)
+{}
+// note: range includes low but excludes high: [low,high) (like stl)
+// note: [foo,foo) is considered the empty set
+bool Cursor::setRange( off_t low, off_t high )
+{
+  if ( low > high )
+    return false;
+  _low = low;
+  _high = high;
+  return true;
+}
+
+off_t Cursor::decrByByte( off_t n )
+{
+  // check for underflow
+  if (n > _byteOffset)
+    return OutOfRange;
+  else
+    _byteOffset -= n;
+  return _byteOffset;
+}
+off_t Cursor::decrByChar( off_t n )
+{
+  off_t byteDelta = n/_charsPerByte;
+  off_t charDelta = n%_charsPerByte;
+  
+  if ( charDelta > _charOffset ) {
+    if( byteDelta == MAX_OFFSET ) {
+      throw out_of_range("Cursor decriment underflowed.\n");
+    }
+    byteDelta++;
+  }
+  // if underflow.. then just return
+  if( byteDelta && OutOfRange == decrByByte( byteDelta ) ) {
+      return _charOffset;
+  }
+  if ( charDelta > _charOffset ) {
+    // offset == maxidx - abs(_charOffset - charDelta)
+    _charOffset = (_charsPerByte) - (charDelta - _charOffset);
+  } else {
+    _charOffset -= charDelta;
+  }
+  return _charOffset;
+}
+// note: off_t is always positive
+off_t Cursor::incrByChar( off_t n )
+{
+  off_t byteDelta = n/_charsPerByte;
+  off_t charDelta = n%_charsPerByte;
+
+  // carry
+  if ( charDelta + _charOffset >= _charsPerByte ) {
+    // Note: this cannot overflow unless chars perbyte == 1
+    if (  byteDelta == MAX_OFFSET ) {
+      throw out_of_range("Cursor increment exceeded maximum offset.\n");
+    }
+    byteDelta++;
+  }
+  // if out of range, just leave the char offset where it is
+  if( byteDelta && OutOfRange == incrByByte( byteDelta ) ) {
+      return _charOffset;
+  }
+  // limit _charOffset to _charsPerByte - 1
+  _charOffset = (charDelta + _charOffset)%_charsPerByte;
+  return _charOffset;
+}
+
+off_t Cursor::incrByByte( off_t byteDelta )
+{
+  if ( byteDelta > MAX_OFFSET - _byteOffset ) {
+    throw out_of_range("Cursor increment exceeded maximum offset.\n");
+  }
+  if ( _byteOffset + byteDelta >= _high ) 
+    return OutOfRange;
+  return (_byteOffset += byteDelta);
+}
+
+//
+// accessor implimentations
+//
+off_t Cursor::byteOffset() const
+{
+  return _byteOffset;
+}
+off_t Cursor::charOffset() const
+{
+  return _charOffset;
+}
+#define MIN(a,b) (a < b)?a:b
+off_t Cursor::setCharsPerByte( off_t charsPerByte )
+{
+  _charsPerByte = charsPerByte;
+  _charOffset = MIN(_charOffset,charsPerByte-1);
+  return _charsPerByte;
+}
+// _byteOffset values are clamped to:
+// [_low,_high)
+// _charOffset values are clamped to:
+// [0,_charsPerByte-1]
+void Cursor::setOffset( off_t byteOffset, off_t charOffset )
+{
+  assignClamped(_byteOffset,byteOffset,0,_high);
+  assignClamped(_charOffset,charOffset,0,_charsPerByte);
+}
+off_t Cursor::charOffsetAbsolute() const
+{
+  return _byteOffset*_charsPerByte + _charOffset;
+}
+//
+// void Cursor::assignClamped(dst,src, low,high);
+// convienience function for assigning dst = src
+// clamped to [low,high)
+//
+void Cursor::assignClamped(off_t& dst, off_t src, off_t low, off_t high)
+{
+  if( src < low ) {
+    dst = low;
+  } else if( src >= high ) {
+    dst = high-1;
+  } else {
+    dst = src;
+  }
+}