no-reply@allegro.cc (jmasterx) — Wed, 25 Jul 2012 01:39:43 +0000

I used to use ifstream everywhere and used getline(ifs,line) to get a line of text. I'm trying to create a function that does the same thing. Instead of using streams I'm now creating my own File class which utilizes PhysFS.

Here is my class:

#SelectExpand
  1#include "Game/Utility/File.hpp"
  2namespace cge
  3{
File::File(void)
  : m_file(NULL)
{
}
  8
File::File( const std::string& fileName, const std::string& openMode /*= "r"*/ )
  : m_file(NULL)
{
  open(fileName,openMode);
}
 14
File::~File(void)
{
}
 18
bool File::isOpen() const
{
  return m_file != NULL;
}
 23
bool File::open( const std::string& fileName, const std::string& openMode )
{
  m_file = al_fopen(fileName.c_str(),openMode.c_str());
 27
  return m_file != NULL;
}
 30
bool File::close()
{
  if(isOpen())
  {
    al_fclose(m_file);
    m_file = NULL;
    return true;
  }
  return false;
}
 41
bool File::eof() const
{
  if(!isOpen())
  {
    return true;
  }
  else
  {
    return al_feof(m_file);
  }
}
 53
bool File::readLine( std::string& buff )
{
  buff = "";
  if(eof() || !isOpen())
  {
    return false;
  }
 61
  
  int c = 0;
  while((c = al_fgetc(m_file)) != EOF && c != '\n')
  {
    buff += static_cast<char>(c);
  }
 68
  return !eof();
}
 71}

It seems to almost work, but not quite, a few of my files and a few of my resources are not having lines read correctly from them. Is there something I'm not considering?

For example, I have code that reads backgrounds:

#SelectExpand
bool BackgroundManager::_loadBackgrounds( 
  const std::string& path, const std::string& bgFile )
{
  std::string fullPath = path + bgFile;  
  5
  _cleanBackground();
  _cleanBackgrounds();
  m_backgrounds.clear();
  9
  //open the file
  File ifs( fullPath );
 12
  //ensure it is open
  if(!ifs.isOpen())
  {
    return false;
  }
  std::string line;
 19
  //read each line
  while( ifs.readLine(line) )
  {
 23
    if(line.length() == 0)
    {
      continue;
    }
    else if(line.length() >= 1 && line[0] == '#')
    {
      continue;
    }
 32
    if(line.length() >= 1 && line[0] != '@')
    {
      continue;
    }
 37
    //name, background, offsetX, offsetY, scale, thumbnail 
    std::string attrib[6];
    Sprite* bgThumbImg = NULL;
 41
    for(int i = 0; i < 6; ++i)
    {
        if(!ifs.readLine(line))
        return false;
 46
      int pos = -1;
      for(size_t j = 0; j < line.length(); ++j)
      {
        if(line[j] == ':')
        {
          pos = j;
          break;
        }
      }
 56
      //need 6 valid attributes
      if(pos == -1)
      {
        return false;
      }
 62
      //move to first character
      pos+= 2;
      if(pos < (int)line.length())
      {
        attrib[i] = line.substr(pos);
      }
    }
 70
    if(attrib[5] != "")
    {
      bgThumbImg = new Sprite(attrib[5]);
    }
 75
    float values[3] = { 0.0f,0.0f,0.0f };
 77
    int j = 0;
    for(int i = 2; i < 5; ++i, ++j)
    {
      std::stringstream ss;
      ss << attrib[i];
      ss >> values[j];
    }
 85
    m_backgrounds.push_back(BackgroundData(bgThumbImg,path + attrib[1],values[0],
      values[1],values[2],attrib[0]));
  }
 89
  return true;
}

Sample Background file:

@default background
Name: Blue Marble Floor
Background: default.bg.png
OffsetX: 0.225
OffsetY: 0.225
Scale: 1.0
Thumbnail:

Although it seems like it loads all 6 parameters for the background, but the code never reaches the new Sprite call. Certain files load fully and some fail to read certain lines. I'm puzzled.

Thanks

no-reply@allegro.cc (Arthur Kalliokoski) — Wed, 25 Jul 2012 01:43:30 +0000

Sledgehammers to swat mosquitoes...

http://www.allegro.cc/manual/5/al_fgets

no-reply@allegro.cc (jmasterx) — Wed, 25 Jul 2012 01:49:54 +0000

I was aware of that but was hoping to have an arbitrarily long line, not something like char tmpBuff[4096].

no-reply@allegro.cc (Arthur Kalliokoski) — Wed, 25 Jul 2012 01:53:15 +0000

So if strlen() says your buffer is full, realloc() it to be larger and try again. Oh, wait, C++ can't do that, sorry.

no-reply@allegro.cc (jmasterx) — Wed, 25 Jul 2012 02:08:16 +0000

Changed return !eof(); to return true and that fixed it. And I didn't even need realloc . Thanks

no-reply@allegro.cc (Luiji99) — Wed, 25 Jul 2012 08:59:43 +0000

Arthur Kalliokoski said:

So if strlen() says your buffer is full, realloc() it to be larger and try again. Oh, wait, C++ can't do that, sorry.

C++ can call both strlen and realloc in exactly the same way as C, but that method wouldn't work anyway.

Also, constantly appending individual characters to a C++ string will result in a number of realloc calls internally, so deciding on a maximum buffer size, running al_gets and then creating a string from that. Its less flexible, but its faster.

no-reply@allegro.cc (jmasterx) — Wed, 25 Jul 2012 09:26:03 +0000

The way I get around that is by calling str.reserve(512) or something. This way it only reallocs if I have something really big. For me this way offers more flexibility than a fixed size.

no-reply@allegro.cc (Luiji99) — Wed, 25 Jul 2012 11:08:19 +0000

True. It still has the overhead of constant function calls, but that would provide a nice balance between flexibility and speed.

What's wrong with my readline function?