I need to convert this progra in C to C++

I wrote this program in C and now i need to change it to C++.Its quite long, so im not going to put all code in here. I just want to know how to convert it to C++, like the differences between this 2 languages Sorry for the indentation.. i didnt had time to put this code in a good indentation

  #include <ctype.h>
  #include <string.h>
  #include <malloc.h>
  #include "lexer.h"

  #pragma warning(disable : 4996) 

  int currentToken;
  char *token_ptr;
  char token[255];
  char *lexer_str;  // pointer to the start of the string
  int * token_positions;
  int n_tokens;

     // checks if the first characters of token_ptr are equal to the given                   string
  int firstEqual(char *str)
    {
      char *tk = token_ptr;
        for (;*tk == *str && *tk && *str; tk++, str++);
          return *str == '\0';
    }

   // skips spaces and comments
   void skipSpaces()
  {
      while (*token_ptr && isspace(*token_ptr)) token_ptr++; // skip spaces

        if (!*token_ptr)
        {
           return;
        }

        if(firstEqual("/*")) // there is a comment here... skip it!
        {
           token_ptr += 2;
    while (*token_ptr && !firstEqual("*/"))
        token_ptr++;
    token_ptr += 2;
    skipSpaces();
}
}

  void initLexer(char * str)
  {
lexer_str = token_ptr = str;
token_positions = (int *)malloc(sizeof(int) * 1000000); // up to one million tokens
n_tokens = 0;
   }

   /* adds a new token to the token list */
  void addToken(int tk_id, int length)
   {
token_positions[n_tokens++] = token_ptr - lexer_str;
currentToken = tk_id;
strncpy(token, token_ptr, length);
token[length] = '\0';
token_ptr += length;

  }

  int nextToken()
  {
skipSpaces();

if (*token_ptr)
{
    if (isalpha(*token_ptr)) // a letter
    {
        // isolate the next token
        char * tk_end = token_ptr + 1;
        while (*tk_end && (isalnum(*tk_end) || *tk_end == '_')) *tk_end++;
        int length = tk_end - token_ptr;
        strncpy(token, token_ptr, length);
        token[length] = '\0';
        // check if is a keyword
        if (!strcmp(token, "array"))
        {
            addToken(TK_ARRAY, length);
        }
        else if (!strcmp(token, "break"))
        {
            addToken(TK_BREAK, length);
        }

        else  // not a keyword... must be an id
        {
            addToken(TK_ID, length);
        }
    }
    else if (isdigit(*token_ptr)) // a digit
    {
        int length = 0;
        while (*token_ptr && isdigit(token_ptr[length])) length++;
        addToken(TK_INT, length);
    }
    else if (*token_ptr == '"') // a string
    {
        char * tk_end = token_ptr + 1;
        while (*tk_end && *tk_end != '"') tk_end++;
        int length = tk_end - token_ptr + 1;
        addToken(TK_STRING, length);
    }
    else if (firstEqual(":=")) // an assignment
    {
        addToken(TK_ASSIGN, 2);

else // no more tokens!
{
    currentToken = TK_END_INPUT;
    return 0;
}

  void prevToken()
  {
if (n_tokens > 0)
{
    n_tokens--;
    token_ptr = lexer_str + token_positions[n_tokens];
}
  }

Now i need to convert this 'program' above into C++. Can someone help? Thank you so much