Question

Hi every one I have the following problem I need to build a vector array from a file.
I managed to creat a vector by reading the file into a string buffer then saving it into this following vector.

vector<char> pattern(contents.begin(), contents.end());

But I have the following function that I need to pass the vector to.

void WuManber::Initialize( const vector<const char *> &patterns, 
                      bool bCaseSensitive, bool bIncludeSpecialCharacters, bool bIncludeExtendedAscii )

how can I read from a file a passable vector to this function.
thank you for your help.

to elaborate more I need it to do the following

for ( size_t q = m; q >= B; --q ) 
  { // start loop -8-

  unsigned int hash;
  hash  = m_lu[patterns[j][q - 2 - 1]].offset; // bring in offsets of X in pattern j
  hash <<= m_nBitsInShift;
  hash += m_lu[patterns[j][q - 1 - 1]].offset;
  hash <<= m_nBitsInShift;
  hash += m_lu[patterns[j][q     - 1]].offset;
  size_t shiftlen = m - q;
  m_ShiftTable[ hash ] = min( m_ShiftTable[ hash ], shiftlen );
  if ( 0 == shiftlen ) 
 {  // start if -8-
    m_PatternMapElement.ix = j;
    m_PatternMapElement.PrefixHash = m_lu[patterns[j][0]].offset;
    m_PatternMapElement.PrefixHash <<= m_nBitsInShift;
    m_PatternMapElement.PrefixHash += m_lu[patterns[j][1]].offset;
    m_vPatternMap[ hash ].push_back( m_PatternMapElement );
  } // end if -8-

int main(int argc, char* argv[])
{
if (argc < 2) {
  std::cout << "usage: " << argv[0] << " <filename>\n";
  return 2;
 }

 ifstream fin(argv[1]);
 if (fin) {
  stringstream ss;
  // this copies the entire contents of the file into the string stream
  ss << fin.rdbuf();
  // get the string out of the string stream
  string contents = ss.str();
  cout << contents;
  // construct the vector from the string.
  vector<char> pattern(contents.begin(), contents.end());
  Initialize( &pattern);
  cout << pattern.size();
 }
 else {
  cout << "Couldn't open " << argv[1] << "\n";
  return 1;
 }
 return 0;
}

Answer 1

The function is looking for a vector of C strings (that’s the most likely meaning of const char * inside a container named patterns.

Here is how you can build one:

std::vector<const char*> patterns;
patterns.push_back("my-first-pattern");
patterns.push_back("my-second-pattern");

If you or your team designed this function, you may want to suggest changing the container type to a more C++ – ish vector<string>.

If you are reading your patterns from a file, you can populate your array as follows:

EDIT (in response to a comment)

std::ifstream ifs("file_with_patterns.txt");
std::vector<const char*> patterns;
while (!ifs.eof()) {
    std::string buf;
    std::getline(ifs, buf);
    patterns.push_back(strdup(buf.c_str()));
}