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-rwxr-xr-xcursor.cpp158
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diff --git a/cursor.cpp b/cursor.cpp
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+/* $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;
+ }
+}