offset

How can I find the max offset?

Code:

---

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define MAXCHAR 2048    //number of characters to read from disk

int main(void)
{
    char filename[256];
    char text[256];
    long x;
    char buffer[MAXCHAR+1];
    FILE *f;
    long matches = 0;
    char *a;



    printf("Filename:");    //Get filename
    gets(filename);
 

    if((f = fopen(filename,"rb")) == NULL)
    {
        printf("Error opening %s\n",filename);
        exit(0);
    }
                            //Get search string
    printf("Hunt for text:");  //Edit this to look for MC FFD9 03B
    gets(text);

    printf("\nLooking in %s for \"%s\" . . .\n",filename,text);

    printf(">> %s found\n",filename);
    printf(">> Hunting for \"%s\"\n",text);

/* Scan for a matching byte */

    x = 1;                  //File offset

    while(fgets(buffer,MAXCHAR,f))
    {
        if( (a = strstr(buffer,text)) != NULL)
        {
            matches++;      //inc. match count
            printf("Found at offset %Lu\n",x+a-buffer);
   
        }
        x+=strlen(buffer);      //adjust offset
    }

    fclose(f);
}

---

On a side note, don't use gets() use fgets() instead the reason behind this is explained in the FAQ:
http://faq.cprogramming.com/cgi-bin/...&id=1043284351

I need to search a file for a certain characters and report were it is in the file. I need too test if the characers are the ones just before the EOF or not.

Best solution I can come up with is too strrchr then copy the what remains of the text file. If only the strch charecter is left then it is just before the EOF. Anyone have a better method?

I'm not sure I understand your question, but here goes:

Code:

---

/* Scan for a matching byte */

    offset = -1;
    x = 1;                  //File offset

    while(fgets(buffer,MAXCHAR,f))
    {
        if( (a = strstr(buffer,text)) != NULL)
        {
            matches++;      //inc. match count
            printf("Found at offset %Lu\n",x+a-buffer);
            offset = x + a - buffer;
   
        }
        x+=strlen(buffer);      //adjust offset
    }
    if (offset != -1)
      printf("last match found at offset: %d\n",offset);
    printf("end of file at offset: %d\n",x);

---

The best I've been able to string this together, since Rhidian has spread questions and various fragments from replies around various threads and forums, is like this:

Search through a file (likely a JPEG) opened in binary mode and search for this format's end-of-file indicator, which happens to be a hex value such as FFD9.

A quick hack, since I'm not exactly sure that this is what Rhidian is asking, might be something like this.

Code:

---

#include <stdio.h>
#include <stdlib.h>

int main(void)
{
  static const char filename[] = "Ocean Wave.jpg";
  FILE *file = fopen(filename, "rb");
  if ( file != NULL )
  {
      unsigned char *buffer;
      long i, size;

      fseek(file, 0L, SEEK_END);
      size = ftell(file);
      rewind(file);

      buffer = malloc(size);
      if ( buffer != NULL )
      {
        static const unsigned char jpeg_eof[] = {0xFF,0xD9};
        if ( fread(buffer, sizeof *buffer, size, file) == size )
        {
            for ( i = 0; i < size - 1; ++i )
            {
              if ( buffer[i] == jpeg_eof[0] && buffer[i + 1] == jpeg_eof[1] )
              {
                  printf("i = %lX, size = %lX\n", i, size);
                  break;
              }
            }
        }
      }
      free(buffer);
      fclose(file);
  }
  else
  {
      perror(filename);
  }
  return 0;
}

/* my output
i = 121B7, size = 121B9
*/

---

Judging from the comments in Rhidian's code, that looks like what he's after.