anithmetic

which way is the better way ?

i get this error with this line

34 C:\.....cpp [Warning] NULL used in arithmetic

Code:

---

        while(line[buf] != NULL){ cout << line[buf]; buf++; }

---

it still compiles but just gets stuck doing nothing. would

Code:

---

while(line[buf] !=  "" ){ cout << line[buf]; buf++; }

or

 while(line[buf] !=  0  ){ cout << line[buf]; buf++; }

---

be better ? or something else ? thank you.

What do you want to check? Whether line[buf] contains ANY string, or whether the string it contains is empty?

Code:

---

while(line[buf] != NULL){ cout << line[buf]; buf++; }

---

Checks whether it contains any string.

Code:

---

while(line[buf] !=  "" ){ cout << line[buf]; buf++; }

---

Wrong in both cases.

Code:

---

while(line[buf] !=  0  ){ cout << line[buf]; buf++; }

---

Same as the first one.

Code:

---

  while (!in.eof())
          {
                  getline (in, line);
                  meta = line.find("meta");
                  if(meta >= 0)
                  {
                        cout << "\nmeta == " << fileline << "\n" << endl;
                       
                        name = line.find("data");
                        buf = name + 12;
                        cout << "meta: ";
                        while(line[buf] != NULL){ cout << line[buf]; buf++; }
                        cout << endl;

---

both ? how about the end of the tag data ?

prog looks for "meta" tag data inside a file. reads data in to variable and puts that out to the screen. problem is finding end of tag data. there are several strings as far as i can tell. then more of the file. want to read all the strings in the right variable. thinking that this could be redone as a structure and then filled. i need to do some more reading on tags and see if i can find the one this file uses. then i should have some reference as to how long each string is.

figured out why it just sits there doing nothing. there was no "meta" tag in side the file. i opened the file with notepad. there were other tags in there. as i said i need to find the info on which tag this file uses. thank you for the reply and it helped me realize that i was missing the info i needed to do the program.

1. From where the variable fileline is accessed? (As i can't see through your whole code, anyways let i suppose it's initialized or set somewhere.)
2. Okay, let take a case.
e.g. Your line array contains: "My meta found a huge data"
When you first find meta, it should return 3 and within loop when you find data it should return 21, and you add 12 in it which makes buf as 33 and your string is of length less than 33.

You should check if the second find actually succeeds.
Furthermore, it is bad to use eof as loop control. There IS a faq about that on the site.
And finally, I have no idea what this piece is supposed to do:

Code:

---

while(line[buf] != NULL){ cout << line[buf]; buf++; }

---

i did not write the original program. i only tried to modify it to do what i wanted. thank you for the suggestions. i am going to read through the faq again. that line i thought reads in the tag line and puts it in the buffer and then increments the count. guess not. going to restart. first when i find the info on the wright tag then i will apply that.

We cannot see how "line" is declared.
And the...
line[buf] != NULL
...looks suspicious.

it is defined as a string. as i said i am going to start over with this project. i just needed something quick to check the tags.

[code ]
string line;
[/code]

TIFF Tag Reference, EXIF Tags

ok here is the redo. this is what i have so far. some work on the structure is yet needed.

Code:

---

/* metatagreadertwo0001.cpp */

#include <windows>
#include <fstream>
#include <iostream>
#include <string>

using namespace std;

int main() {
   
    struct camm {
                  ExposureTime
                  FNumber
                  ExposureProgram
                  SpectralSensitivity
                  ISOSpeedRatings
                  OECF
                  ExifVersion
                  DateTimeOriginal
                  DateTimeDigitized
                  ComponentsConfiguration
                  CompressedBitsPerPixel
                  ShutterSpeedValue
                  ApertureValue
                  BrightnessValue
                  ExposureBiasValue
                  MaxApertureValue
                  SubjectDistance
                  MeteringMode
                  LightSource
                  Flash
                  FocalLength
                  SubjectArea
                  MakerNote
                  UserComment
                  SubsecTime
                  SubsecTimeOriginal
                  SubsecTimeDigitized
                  FlashpixVersion
                  ColorSpace
                  PixelXDimension
                  PixelYDimension
                  RelatedSoundFile
                  FlashEnergy
                  SpatialFrequencyResponse
                  FocalPlaneXResolution
                  FocalPlaneYResolution
                  FocalPlaneResolutionUnit
                  SubjectLocation
                  ExposureIndex
                  SensingMethod
                  FileSource
                  SceneType
                  CFAPattern
                  CustomRendered
                  ExposureMode
                  WhiteBalance
                  DigitalZoomRatio
                  FocalLengthIn35mmFilm
                  SceneCaptureType
                  GainControl
                  Contrast
                  Saturation
                  Sharpness
                  DeviceSettingDescription
                  SubjectDistanceRange
                  ImageUniqueID
                  }
                 
                 
                 
                 
                 
                 
   
    int count;
    string buff[256];
 
  ifstream in( "CDSC000032.jpg" );
 
    string s;
  while(getline(in, s)) // Discards newline char
    out << s << "\n"; // .... must add it back
}

---