reading files byte by byte

[dip7]

Hi,
I have come up with the source code to read files. However, this is source code reads the file 1024 bytes at a time. I would like to modify the code to read it byte by byte.

This code wants to determine if 001 bytes ( oo oo o1 hex) is present in the file.

I wish to eliminate the use of buffer. Can someone kindly guide me please? Thank you very much.

#include<stdio.h>
#include<iostream>

using namespace std;

int main(void)
{


FILE *stream = fopen("Celine.jpg","rb");


         char buffer[1024]; 
         int bytesRead;
         bool startPrefixFound;
         

         while (bytesRead = fread( buffer,1, 1024, stream))
         {
               startPrefixFound = false;
               for (int i = 0; i < bytesRead-3; i++)
               {
                   if (buffer[i]==0)
                   {
                                    if (buffer[i+1]==0)
                                    {
                                                       if (buffer[i+2]==0)
                                                       {
                                                                          if (buffer[i+3]==1)
                                                                          {
                                                                                             startPrefixFound = true;
                                                                                             printf("001 bytes found. May be H.264 file type");
                                                                                             break;
                                                                          }
                                                       }
                                    }                  
                   }                                                         
               }                                    
               
               if (startPrefixFound) break;
               printf("001 bytes not found. Definitely not H.264 file type");
               break;
              
              }
cin.ignore();
cin.get();

return 0;
}

[Narue]

int byte;

while ((byte = getc(stream)) != EOF) {
    /* ... */
}

[Ancient Dragon]

replace fread() with fgetc(). Of course you will have to deleted and rewrite eveything inside that while loop.

[dip7]

I have modified this code but there is still errors. Can you guide me on this please? Thank you.

#include<stdio.h>
#include<iostream>
#include<cstdio>

using namespace std;

int main(void)
{


FILE *stream = fopen("test","rb");

int fgetc(FILE *stream);
         char c;
         bool startPrefixFound;
         c=fgetc(stream);
         
         while (c!= EOF) {

               
                    startPrefixFound = false;
                    for (int i = 0)
                    {
                    if (c[i]==0)
                       {
                                    if (c[i+1]==0)
                                    {                                                  
                                                               if (c[i+2]==1)           
                                                                          {
                                                                                startPrefixFound = true;
                                                                                printf("001 bytes found. May be H.264 file type");
                                                                                break;
                                                                          }
                                                       
                                    }                  
                   }         
                   i++;                                                
               }           
               }                         
               
               if (startPrefixFound) break;
               printf("001 bytes not found. Definitely not H.264 file type");
               break;
              
              
cin.ignore();
cin.get();

return 0;
}

[WaltP]

1) Format your code properly -- How to do it. Concentrate in INDENTING.
2) We aren't Psychic! "there is still errors" is no help at all. Are we supposed to guess what the errors are?

[Narue]

You only call fgetc once. Either add it to your loop condition as per my example, or call it again at the end of the loop body.

>for (int i = 0)
You should read up on how for loops work.

Finally, you have two break statements that are outside of any loop, which isn't valid syntax.

[dip7]

Thank you Narue for your guidance. I am a beginner to C++. Your reply is really useful to me, unlike that of WaltP.

[dip7]

Hi,

I have modified my program.

However, i receive these 2 errors: 1) [Linker error] undefined reference to `fgetc(_iobuf*)' 2)ld returned 1 exit status.

Do you know where have i gone wrong? I have checked it many times. But am still not able to solve this.

#include<stdio.h>
#include<iostream>
#include<fstream>
#include<cstdio>

using namespace std;

int main(void)
{


FILE *stream = fopen("celine.jpg","rb");

         int fgetc(FILE *stream);
         int numZeros=0;
         char c;
         
         c=fgetc(stream);
         
         while (c!= EOF) {

               
                   if(c==0) 
                   numZeros=numZeros+1;
        
                   else if (c==1 && numZeros ==2)
                   {
                   printf("001 bytes found. May be H.264 file type");
                   break;
                   }                                                       
                                                       
                   else
                   printf("001 bytes not found. Definitely not H.264 file type");
                   }
        fclose(stream);
              
cin.ignore();
cin.get();

return 0;
}

[chiwawa10]

You are getting the codes wrong. Particularly at line 14

int fgetc(FILE *stream);

This line is not needed.
Line 18 until line 34 (while loop) can be rewritten like below

c = fgetc(stream);
while(c != EOF)
{
     // logic goes here

     c = fgetc(stream);
}

[Ancient Dragon]

It can also be rewritten as

int c;
while( (c = fgetc(stream)) != EOF)
{
   // do something here
}

Notice there is only one call to fgetc(), not two. Also not that fgetc() returns an int, not char because EOF may or may not fit in a char variable.