How to get ASCII value from String class?

[ChuckB]

Hi,
I have a string with text. I would like to iterate through the string and compare each character to an ASCII number. I cannot find a very clear answer....the only things I can think up requre multiple lines of code.

string text="Good morning";
for(int i = 0; i< text.length(); i++){
  // here is where I need to code to extract a single character
  // using substr and getting the ASCII value.

}

I would like to avoid using char arrays. Is there a nice ANSI C++ way of doing this?

Thanks,
ChuckB

[CornedBee]

What do you want to do when you find the ASCII number?

for(string::iterator i = str.begin(); i != str.end(); ++i)
{
  if(*i == 65)
    cout << "Found an A at index " << (i-str.begin()) << endl;
}

[ChuckB]

Hi CornedBee,
Thanks for the reply. I have a bitmap image with 70 characters of a particular font mapped out on it. I have stored the exact coordinates of these 70 characters in a STL vector So I have a global 'vector <FONT> font'. There exists a font[z].ascii that holds the ascii number (int) of the corresponding font.

I want to read one character at a time from a string 'text' and look in the font[].ascii for a match.

I added your code in mine below. I substituted the 'm' for your 'i'. Also, I got errors manipulating 'text' directly so I had to place the value into another string 'onestr'. No more errors. However, I do not think this code is working correctly....

Any more tips would be helpful.
Regards,
ChuckB

void DrawText2D(int x, int y, int size, const string& text ){
  string onestr=text;  

  glEnable(GL_TEXTURE_2D);
  glBindTexture ( GL_TEXTURE_2D, texture_objects[TEX_FONT1]);
  glBegin(GL_QUADS);

  for(string::iterator m = onestr.begin(); m != onestr.end(); ++m)
  {

    for (int z=1;z < 70; z++){ //scroll through font vector looking for match
      
      if( *m == font[z].ascii){
        glTexCoord2f(font[z].a.x, font[z].a.y);
        glVertex2f(x + step * size, y );

        . . . etc.

[CornedBee]

Use string::const_iterator instead of string::iterator, then you don't need to copy the string.

You have 70 characters? This is a static number, isn't it? You should use a static array instead of the vector then.

Or even better (as it would speed things up) you could use an STL map:

#include <map>

struct CHARACTER {
  POINT a;
  DIMENSION b;
};

typedef std::map<char, CHARACTER>  font_map;
typedef std::map<char, CHARACTER>::const_iterator font_map_const_iter;
typedef std::map<char, CHARACTER>::value_type font_map_value;

font_map characters;
// Needs code to fill the map.
// The map is filled like this:
void addEntry(char code, const CHARACTER &ch) {
  character.insert(font_map_value(code, ch));
}

void DrawText2D(int x, int y, int size, const string& text ){
  glEnable(GL_TEXTURE_2D);
  glBindTexture ( GL_TEXTURE_2D, texture_objects[TEX_FONT1]);
  glBegin(GL_QUADS);

  for(string::const_iterator m = text.begin(); m != text.end(); ++m)
  {
    font_map_const_iter pch = characters.find(*m);
    glTexCoord2f(pch->second->a.x, pch->second->a.y);
    glVertex2f(x + step * size, y );

    . . . etc.

[ChuckB]

Wham! I feel like I just gut hit by a Mack truck! :-)

Corned Bee, thanks, but that is a bit too much for me to absorb at this instant. I have been stuck on vectors after I found out about them. I guess I need to expand my knowledge of STL. Maybe soon.

I will apply the const_iterator to my code to get rid of that one extra string variable. I am copying this last example of yours to print out...and study later on.

Thanks again.
ChuckB

[ChuckB]

CornedBee,

Will you give me some feedback on this...

  ostringstream Str;

  . . . .

  for(string::const_iterator m = text.begin(); m != text.end(); ++m)
  {
    Str << *m;
    string mynum(Str.str());
    LogData(mynum);

The LogData is a function I wrote that receives a string. I make 'text' above = "Good Morning". From what you have written, doesn't '*m' have the ASCII value of the character being examinged? My little code converts the integer *m into a string for writing to a file.

I was really expecting to see ASCII numbers.
Regards,
ChuckB

[CornedBee]

The data type of the iterator dereferenced is still char, not int. An inserting a character into a stream means that it is interpreted as character. The solution is to cast it.

  ostringstream Str;

  . . . .

  for(string::const_iterator m = text.begin(); m != text.end(); ++m)
  {
    Str << (int)*m << ' ';
    string mynum(Str.str());
    LogData(mynum);

[parksie]

When using a map<>, make sure to test for a return value of yourmap.end(), since it may not be found.

[CornedBee]

Right.
if(pch == characters.end())
// not found

[ChuckB]

Corned Bee,
Thanks a bunch! The casting of (int)*m was right on and got me going. Thanks. I am attaching a screenshot showing the bitmap font...thanks to you for the final fix. Your code and final clue helped me scroll through my font data to match the ASCII value. :-)

[ChuckB]

Oh Yeah! The spacing in the text in the above graphic was intentional experimentation. :-)