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/*
* Copyright (C) 2007-2008 Xagasoft, All rights reserved.
*
* This file is part of the libbu++ library and is released under the
* terms of the license contained in the file LICENSE.
*/
#ifndef BU_BITSTRING_H
#define BU_BITSTRING_H
#include "bu/util.h"
#include "bu/fstring.h"
namespace Bu
{
/**
* Manages an arbitrarily sized string of bits, and allows basic interaction
* with them. This includes basic non-mathematical bitwise operations such
* as setting and testing bits, shifting the string, inversion and a few
* extras like randomization. On linux systems this takes advantage of long
* longs giving you a maximum size of about 2tb per string.
*
* For more general and mathematical type interaction see BitStringInt.
*
*/
class BitString
{
public:
/**
* Constructs a blank and basic BitString. This is actually useful
* since you can resize BitStrings at will, and even retain the data
* that was in them.
*/
BitString();
/**
* Constructs a BitString object as a copy of another BitString. This
* is a standard copy constructor and produces an exact duplicate of
* the original BitString object.
*@param xSrc Source BitString to copy data from.
*/
BitString( const BitString &xSrc );
/**
* Constructs a BitString with length iBits and optionally fills it with
* random data. The default setting, to not fill randomly, will produce
* a blank (all zeros) string of the specified size.
*@param iBits The length of the new BitString in bits.
*@param bFillRandomly Wether or not to randomize this BitString.
*/
BitString( long iBits, bool bFillRandomly=false );
/**
* Virtual deconstructor for the BitString. Takes care of cleanup for
* you. What more do you really want to know?
*/
virtual ~BitString();
// basic interaction
/**
* Sets a bit in the BitString. In it's normal mode it will always turn
* the given bit on, to clear a bit set bBitState to false instead of
* true. This operation runs in O(1).
*@param iBit The zero-based index of the bit to modify.
*@param bBitState Set to true to set the bit to 1, set to false to set
* the bit to 0.
*/
void setBit( long iBit, bool bBitState=true );
/**
* Reverses the state of the given bit. This will set the given bit
* to a 1 if it was 0, and to 0 if it was 1. This operation runs in
* O(1), and it should be noted that using this is marginally faster
* than doing the test and flip yourself with getBit and setBit since
* it uses a bitwise not operation and doesn't actually test the bit
* itself.
*@param iBit The index of the bit to flip.
*/
void flipBit( long iBit );
/**
* Gets the state of the given bit. This follows the standard
* convention used so far, a returned value of true means the bit in
* question is 1, and a value of flase means the bit is 0. All bits
* out of range of the BitString are treated as off, but are
* "accessable" in that this does not produce any kind of error
* message. This is intentional. This operation runs in O(1).
*@param iBit The index of the bit to test.
*@returns True for a 1, false for a 0.
*/
bool getBit( long iBit );
/**
* Inverts the entire BitString, in effect this calls flipBit on every
* bit in the string but is faster since it can operate on whole bytes
* at a time instead of individual bits. This operation runs in O(N).
*/
void invert();
/**
* Returns the number of bits allocated in this BitString. This
* operation runs in O(1) time since this value is cached and not
* computed.
*@returns The number of bits allocated in this BitString.
*/
DEPRECATED
long getBitLength();
long getSize();
/**
* Sets the entire BitString to zeros, but it does it very quickly.
* This operation runs in O(N).
*/
void clear();
/**
* Gets another BitString that is autonomous of the current one
* (contains a copy of the memory, not a pointer) and contains a subset
* of the data in the current BitString. This is an inclusive
* operation, so grabbing bits 0-5 will give you 6 bits. This is based
* on a very tricky bit-shifting algorithm and runs very quickly, in
* O(N) time. Passing in a value of zero for iUpper, or any value for
* iUpper that is less than iLower will set iUpper equal to the number
* of bits in the BitString.
*@param iLower The first bit in the current string, will be the first
* bit (0 index) in the new sub string.
*@param iUpper The last bit in the current string, will be the last
* bit in the new sub string. iUpper is included in the sub string.
*@returns A new BitString object ready to be used. Please note that
* managing this new object is up to whomever calls this function.
*/
class BitString getSubString( long iLower, long iUpper );
/**
* Sets the number of bits in the BitString, allocating more memory if
* necesarry, or freeing extra if able. The default operation of this
* function clears all data in the BitString while resizing it. If you
* would like to keep as much of the data that you had in your BitString
* as possible, then set bClear to false, and any data that will fit
* into the new BitString length will be retained. If increasing the
* number of bits, the new bits will come into existance cleared (set
* to 0).
*@param iLength The number of bits to set the BitString to.
*@param bClear When true, all data is eradicated and zeroed, when set
* to false an effort is made to retain the existing data.
*@returns true on success, false on failure.
*/
DEPRECATED
bool setBitLength( long iLength, bool bClear=true );
bool setSize( long iLength, bool bClear=true );
/**
* Randomize the entire BitString, one bit at a time. This is actually
* the function called by the constructor when the user selects initial
* randomization. This function uses the system random() function, so
* srandom may be used to effect this process at will.
*/
void randomize();
/**
* Operates exactly like <<. All data in the BitString is shifted to
* the left by some number of bits, any data pushed off the edge of the
* BitString is lost, and all new data coming in will be zeroed.
* Using a negative value in the shiftLeft function will turn it into
* the shiftRight function.
*@param iAmt The number of bit positions to shift all data.
*/
void shiftLeft( long iAmt ); // just like <<
/**
* Operates exactly like >>. All data in the BitString is shifted to
* the right by some number of bits, any data pushed off the edge of the
* BitString is lost, and all new data coming in will be zeroed.
* Using a negative value in the shiftRight function will turn it into
* the shiftLeft function.
*@param iAmt The number of bit positions to shift all data.
*/
void shiftRight( long iAmt ); // just like >>
/**
* Searches through the BitString and returns the index of the highest
* order bit position (the highest index) with an on bit (a bit set to
* 1). This is a handy helper function and rather faster than calling
* getBit() over and over again.
*@returns The index of the highest indexed on bit.
*/
long getHighestOrderBitPos();
// Conversion
/**
* Convert a block of data (no more than 32 bits) to a primitive long
* type.
* This is done in a little bit interesting way, so it may not always be
* the fastest way to access the data that you want, although it will
* always ensure that the long that is written makes numerical sense, as
* we write numbers, regaurdless of platform.
*@param iStart The first bit in the BitString to include in the long
*@param iSize THe number of bits to include, if this value is set over
* 32 it will be automatically truncated to, or however many bits there
* are in a long in your system.
*@returns A long converted from your raw BitString data.
*/
long toLong( long iStart = 0, long iSize = 32 );
Bu::FString toString();
//operators
BitString &operator=( const BitString &xSrc );
BitString operator~();
BitString operator<<( const long iAmt );
BitString operator>>( const long iAmt );
private:
void fixup();
void setMask();
unsigned char *caData;
long iBits;
long iBytes;
unsigned char cTopByteMask;
};
};
#endif
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