 #include <cassert>
#include <cstring>
#include <cstdlib>
#include <cstdio>
#include <cstdint>
#include <iostream>

using namespace std;


class CFile
{
    public:
        CFile(void); // copy cons, dtor, op=
        CFile(const CFile &src);
        CFile & operator = (const CFile &src);
        ~CFile (void);
        uint32_t write ( const uint8_t *src, uint32_t bytes );
        uint32_t read  ( uint8_t * dst, uint32_t bytes );
        bool seek ( uint32_t offset );
        void truncate ( void );
        uint32_t fileSize ( void ) const;
        void addVersion  ( void );
        bool undoVersion ( void );
        void copyWithoudLinkedList( CFile &src );

        uint8_t *m_Data;
        uint32_t m_Len;
        uint32_t m_Position;
        uint32_t m_Capacity;

        size_t m_LenHistory;
        CFile *m_History;

};

CFile::CFile(void)
:m_Data(nullptr), m_Len(0), m_Position(0), m_Capacity(0),m_LenHistory(0), m_History(nullptr)
{
}

CFile::~CFile (void)
{
    delete[] m_Data;

    //Delete linked list
    if (m_History) delete m_History; 
}

CFile* copyLinkedList(CFile *list)
{
    if(list == nullptr) return nullptr;

    CFile* result = new CFile;
    result->m_Capacity = list->m_Capacity;
    result->m_Len = list->m_Len;
    result->m_Position = list->m_Position;
    result->m_LenHistory = list->m_LenHistory;
    result->m_Data = new uint8_t[list->m_Capacity];
    memcpy(result->m_Data, list->m_Data, result->m_Len);
    result->m_History = copyLinkedList(list->m_History);
    
    return result;
}

// Kopírující konstruktor
CFile::CFile(const CFile &src)
: m_Data(new uint8_t[src.m_Capacity]),
  m_Len(src.m_Len),
  m_Position(src.m_Position),
  m_Capacity(src.m_Capacity),
  m_LenHistory(src.m_LenHistory)
{
    memcpy(m_Data, src.m_Data, m_Len);
    m_History = copyLinkedList(src.m_History);
}

void CFile::copyWithoudLinkedList( CFile &src )
{
    m_Capacity = src.m_Capacity;
    m_Len = src.m_Len;
    m_LenHistory = src.m_LenHistory;
    m_Position = src.m_Position;
    m_Data = new uint8_t[src.m_Capacity];

    memcpy(m_Data, src.m_Data, m_Len);
}

uint32_t CFile::fileSize ( void ) const
{
    return m_Len;
}

void CFile::truncate ( void )
{
    m_Len = m_Position;
}

bool CFile::seek ( uint32_t offset )
{
    if(offset>=0 && offset <=m_Len)
    {
        m_Position = offset;
        return true;
    }
    return false;
}

uint32_t CFile::write ( const uint8_t *src, uint32_t bytes )
{
    int lastLen = m_Len;
    if( bytes + m_Len +1 > m_Capacity )
    {
        while( m_Len + bytes + 1 > m_Capacity )
            m_Capacity += m_Capacity/2 +10;

        uint8_t *tmp = new uint8_t [m_Capacity];
        memcpy(tmp, m_Data, m_Len);
        memcpy(tmp + m_Position, src, bytes);
        delete [] m_Data;
        m_Data = tmp;     
    }
    else
        memcpy(m_Data+m_Position, src, bytes);

    m_Position += bytes;
    int k = (m_Position-lastLen);
    
    if(k>0)
        m_Len += k;

    // počet zapsaných bajtů
    return bytes;
}

uint32_t CFile::read( uint8_t * dst, uint32_t bytes )
{
    if(m_Position+bytes <= m_Len)
    {
        memcpy(dst, m_Data+m_Position, bytes);
        m_Position += bytes;
        return bytes;
    }

    bytes = (m_Len-m_Position);
    memcpy(dst, m_Data+m_Position, bytes);
    m_Position += bytes;

    return bytes;
}

CFile & CFile::operator = (const CFile &src)
{
    // Pokud to co mám zkopírovat je rovno danému objektu
    if(this == &src)
        return *this;

    delete [] m_Data;

    m_Data = new uint8_t[src.m_Capacity];
    m_Len = src.m_Len;
    m_Capacity = src.m_Capacity;
    m_Position = src.m_Position;
    m_LenHistory = src.m_LenHistory;
    memcpy(m_Data, src.m_Data, m_Len);
    m_History = copyLinkedList(src.m_History);

    return *this;
}

bool writeTest ( CFile & x, const initializer_list<uint8_t> & data, uint32_t wrLen )
{
  return x . write ( data . begin (), data . size () ) == wrLen;
}

bool readTest ( CFile &x, const initializer_list<uint8_t> & data, uint32_t rdLen )
{
  uint8_t  tmp[100];
  uint32_t idx = 0;

  if ( x . read ( tmp, rdLen ) != data . size ())
    return false;
  for ( auto v : data )
    if ( tmp[idx++] != v )
      return false;
  return true;
}

void CFile::addVersion  ( void )
{
    CFile *tmp = m_History;
    CFile *prev;

    if(!tmp)
    {
        tmp = new CFile();
        tmp->copyWithoudLinkedList(*this);
        this->m_History = tmp;
        this->m_History->m_History = nullptr;
        m_LenHistory++;
    }
    else
    {
        while(tmp)
        {
            prev = tmp;
            tmp = tmp->m_History;
        }
        
        tmp = new CFile();
        tmp->copyWithoudLinkedList(*this);
        prev->m_History = tmp;
        prev->m_History->m_History = nullptr;
        m_LenHistory++;
   }
}

bool CFile::undoVersion ( void )
{
    if(m_LenHistory == 0)
        return false;

    CFile *tmp = m_History;
    CFile *prev;

    while(tmp)
    {
        prev = tmp;
        tmp = tmp->m_History;
    }

    delete [] m_Data;
    m_Data = new uint8_t[prev->m_Capacity];
    m_Len = prev->m_Len;
    m_Capacity = prev->m_Capacity;
    m_Position = prev->m_Position;
    m_LenHistory = prev->m_LenHistory;
    memcpy(m_Data, prev->m_Data, m_Len);


    // Delete last element from linked list
    
    CFile *tmp2 = m_History;
    CFile *prev2;

    while(tmp2 != prev)
    {
        prev2 = tmp2;
        tmp2 = tmp2->m_History;
    }
    delete tmp2;
    prev2->m_History = nullptr;
    return true;
}


int main (void)
{
  CFile f0;
  assert ( writeTest ( f0, { 10, 20, 30 }, 3 ) );
  assert ( f0 . fileSize () == 3 );
  assert ( writeTest ( f0, { 60, 70, 80 }, 3 ) );
  assert ( f0 . fileSize () == 6 );
  assert ( f0 . seek ( 2 ));
  assert ( writeTest ( f0, { 5, 4 }, 2 ) );
  assert ( f0 . fileSize () == 6 );
  assert ( f0 . seek ( 1 ));
  assert ( readTest ( f0, { 20, 5, 4, 70, 80 }, 7 ));
  assert ( f0 . seek ( 3 ));
  f0 . addVersion();
  cout <<" number copies f0: " << f0.m_LenHistory << endl << endl;
  assert ( f0 . seek ( 6 ));
  assert ( writeTest ( f0, { 100, 101, 102, 103 }, 4 ) );
  f0 . addVersion();
  cout <<" m_Data f0: " << f0.m_Data << endl << endl;
  cout <<" m_Data in 1.copy f0: " << f0.m_History->m_Data << endl << endl;
  cout <<" m_Data in 2.copy f0: " << f0.m_History->m_History->m_Data << endl << endl;
  cout <<" number copies f0: " << f0.m_LenHistory << endl << endl;
  assert ( f0 . seek ( 5 ));
  CFile f1 ( f0 );
  cout <<" m_Data f1: " << f1.m_Data << endl << endl;
  cout <<" m_Data in 1.copy f1: " << f1.m_History->m_Data << endl << endl;
  cout <<" m_Data in 2.copy f1: " << f1.m_History->m_History->m_Data << endl << endl;
  cout <<" number copies f1: " << f1.m_LenHistory << endl << endl;

  f0 . truncate ();
  assert ( f0 . seek ( 0 ));
  assert ( readTest ( f0, { 10, 20, 5, 4, 70 }, 20 ));
  assert ( f0 . undoVersion () );
  assert ( f0 . seek ( 0 ));
  assert ( readTest ( f0, { 10, 20, 5, 4, 70, 80, 100, 101, 102, 103 }, 20 ));
  assert ( f0 . undoVersion () );
  assert ( f0 . seek ( 0 ));
  assert ( readTest ( f0, { 10, 20, 5, 4, 70, 80 }, 20 ));
  assert ( !f0 . seek ( 100 ));
  assert ( writeTest ( f1, { 200, 210, 220 }, 3 ) );
  assert ( f1 . seek ( 0 ));
  assert ( readTest ( f1, { 10, 20, 5, 4, 70, 200, 210, 220, 102, 103 }, 20 ));
  
  assert ( f1 . undoVersion () );
  assert ( f1 . undoVersion () );
  assert ( readTest ( f1, { 4, 70, 80 }, 20 ));
  assert ( !f1 . undoVersion () );
    return 0;
}

created 3 years ago

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About C++

C++ is a widely used middle-level programming language.

Supports different platforms like Windows, various Linux flavours, MacOS etc
C++ supports OOPS concepts like Inheritance, Polymorphism, Encapsulation and Abstraction.
Case-sensitive
C++ is a compiler based language
C++ supports structured programming language
C++ provides alot of inbuilt functions and also supports dynamic memory allocation.
Like C, C++ also allows you to play with memory using Pointers.

Syntax help

Loops

1. If-Else:

When ever you want to perform a set of operations based on a condition If-Else is used.

if(conditional-expression) {
   //code
}
else {
   //code
}

You can also use if-else for nested Ifs and If-Else-If ladder when multiple conditions are to be performed on a single variable.

2. Switch:

Switch is an alternative to If-Else-If ladder.

switch(conditional-expression){    
case value1:    
 // code    
 break;  // optional  
case value2:    
 // code    
 break;  // optional  
......    
    
default:     
 code to be executed when all the above cases are not matched;    
}

3. For:

For loop is used to iterate a set of statements based on a condition.

for(Initialization; Condition; Increment/decrement){  
  //code  
}

4. While:

While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.

while (condition) {  
// code 
}

5. Do-While:

Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.

do {  
 // code 
} while (condition);

Functions

Function is a sub-routine which contains set of statements. Usually functions are written when multiple calls are required to same set of statements which increases re-usuability and modularity. Function gets run only when it is called.

How to declare a Function:

return_type function_name(parameters);

How to call a Function:

function_name (parameters)

How to define a Function:

return_type function_name(parameters) {  
 // code
}