1 /* 2 * steghide 0.5.1 - a steganography program 3 * Copyright (C) 1999-2003 Stefan Hetzl <shetzl@chello.at> 4 * 5 * This program is free software; you can redistribute it and/or 6 * modify it under the terms of the GNU General Public License 7 * as published by the Free Software Foundation; either version 2 8 * of the License, or (at your option) any later version. 9 * 10 * This program is distributed in the hope that it will be useful, 11 * but WITHOUT ANY WARRANTY; without even the implied warranty of 12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 13 * GNU General Public License for more details. 14 * 15 * You should have received a copy of the GNU General Public License 16 * along with this program; if not, write to the Free Software 17 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. 18 * 19 */ 20 21 #ifndef SH_CVRSTGOBJECT_H 22 #define SH_CVRSTGOBJECT_H 23 24 #include "common.h" 25 26 class SampleValue ; 27 28 /** 29 * \class CvrStgObject 30 * \brief an object that can hold embedded data 31 * 32 * This abstract base class provides an interface for every class that is able 33 * to hold embedded data. Something that can hold embedded data is essentially 34 * though of as an array of samples. 35 * 36 * Definitions: 37 * Embedded Bit...a bit to be embedded (one bit in the original or extracted embfile) 38 * Sample...the smallest data unit in a file (e.g. a RGB triple, a DCT coefficient) 39 **/ 40 class CvrStgObject { 41 public: 42 /** 43 * get the number of samples in this CvrStgObject 44 **/ 45 virtual unsigned long getNumSamples (void) const = 0 ; 46 47 /** 48 * get the sample at position pos 49 * \param pos the position of a sample (must be in 0...getNumSamples()-1) 50 * \return the sample at the given position 51 * 52 * The sample object is created in this function and should be deleted by the caller. 53 * The derived class should check the condition(s) given above in its Implementation of this function. 54 **/ 55 virtual SampleValue* getSampleValue (const SamplePos pos) const = 0 ; 56 57 /** 58 * replace a sample thus (possibly) altering the value of the bit returned by SampleValue->getBit() 59 * \param pos the position of the sample (must be in 0...getNumSamples()-1) 60 * \param s the sample value that should replace the current sample value (must be of correct type for this CvrStgObject) 61 * 62 * The derived class should check the condition(s) given above in its Implementation of this function. 63 **/ 64 virtual void replaceSample (const SamplePos pos, const SampleValue* s) = 0 ; 65 } ; 66 67 #endif //ndef SH_CVRSTGOBJECT_H 68