Scusate,
ho questa funzione per visualizzare un file di testo:
codice:
#define CR 13            /* Decimal code of Carriage Return char */
#define LF 10            /* Decimal code of Line Feed char */
#define EOF_MARKER 26    /* Decimal code of DOS end-of-file marker */
#define MAX_REC_LEN 1024 /* Maximum size of input buffer */
#define MAX_NUM_LINE 32
#define MAX_LINE_LENGTH 30

int T_fgetc(FILE *input, char *output){
  int  iReturn   = 1;  /* Return value (Innocent until proved guilty) */
  int  iThisChar;      /* Current character */
  int  isNewline = 0;  /* Boolean indicating we've read a CR or LF */
  long lIndex    = 0L; /* Index into read buffer */

  while (1) /* Will exit on error, end of line, or end of file */
  {
    iThisChar = fgetc(input);     /* Read the next character */

    if (ferror(input))            /* Error reading */
    {
      iReturn = -1;           /* Convert to negative number */
      break;
    }

    if (iThisChar == EOF)         /* End of file reached */
    {
 
      if (lIndex > 0)
        ungetc(iThisChar, input);

      else           /* Nothing read but EOF; we're done with the file */
        iReturn = 0;

      break;
    }

    if (!isNewline) /* Haven't read a CR or LF yet */
    {
      if (iThisChar == CR || iThisChar == LF) /* This char IS a CR or LF */
        isNewline = 1;                        /* Set flag */
    }

    else            /* We've already read one or more CRs or LFs */
    {
      if (iThisChar != CR && iThisChar != LF) /* This char is NOT a CR or LF */
      {
        ungetc(iThisChar, input);             /* Put char back in stream */
        break;                                /* Done reading this line */
      }
    }

    output[lIndex++] = iThisChar;             /* Put char in read buffer */

  } /* end while (1) */

  output[lIndex] = '\0';                      /* Terminate the read buffer */
  return iReturn;

} /* end T_fgetc() */

void PrintLine(char *szReadLine,  long lLineCount, long lLineLen, long lThisFilePos, long *lLastFilePos, int  isFilePosErr){
  char *cPtr;
  cPtr = szReadLine;
  for (cPtr = szReadLine; cPtr <= szReadLine + lLineLen; cPtr++)
  {
            switch (*cPtr)
            {
             case 0:          /* Null terminator */
                  break;
             case CR:                /* Carriage return */
                  break;
             case LF:                /* Line feed */
                  printf("\n");
                  break;
             default:                /* A 'real' character */
                  printf("%c", *cPtr);
                  break;
             }
  }
  printf("\n");
  return;

}

int Reader(char* filen, int linestart)
{
  int (*GetLine[1])(FILE*, char*) = { T_fgetc };
  char tmode[5];
  int   iReadMode=0;             /* Index into *GetLine[] array */
  int   iReadReturn;             /* Result of read function */
  int   isFilePosErr;            /* Boolean indicating file offset error */
  long  lFileLen;                /* Length of file */
  long  lLastFilePos;            /* Byte offset of end of previous line */
  long  lLineCount;              /* Line count accumulator */
  long  lLineLen;                /* Length of current line */
  long  lThisFilePos;            /* Byte offset of start of current line */
  char  szReadLine[MAX_REC_LEN];
  FILE *inputFilePtr;            /* Pointer to input file */

  strcpy(tmode, "t");

  if (strcmp(tmode, "t") == 0)
    inputFilePtr = fopen(filen, "r");  /* Open in TEXT mode */

  else if (strcmp(tmode, "b") == 0)
    inputFilePtr = fopen(filen, "rb"); /* Open in BINARY mode */

  if (inputFilePtr == NULL )             /* Could not open file */
  {
    printf("Error opening %s\n", filen);
    return 1;
  }
  
  fseek(inputFilePtr, 0L, SEEK_END);     /* Position to end of file */
  lFileLen = ftell(inputFilePtr);        /* Get file length */
  rewind(inputFilePtr);                  /* Back to start of file */
  
  lLineCount   =  0L; /* No lines read yet */
  lLastFilePos = -1L; /* So first line doesn't show an offset error */
  
  cls();
  while (1)
  {
    isFilePosErr = 0;
    lThisFilePos = ftell(inputFilePtr);
    if (lThisFilePos != lLastFilePos + 1){
                     isFilePosErr = 1;
                     }
      szReadLine[0] = '\0';

    /* Read the next line with the appropriate read function */
    iReadReturn = (*GetLine[iReadMode])(inputFilePtr, szReadLine);

    if (iReadReturn < 0)
    {
      printf("Error reading: %s\n", filen);
      break;
    }
    lLineLen = strlen(szReadLine); /* Get length of line */
    if (lLineLen)                  /* Got some data */
    {
      ++lLineCount;                /* Increment line counter */
    }
    
    if(lLineCount>=linestart && lLineCount<(linestart+MAX_NUM_LINE)){
                 PrintLine(szReadLine, lLineCount, lLineLen, lThisFilePos, &lLastFilePos, isFilePosErr);
    }
    if (iReadReturn == 0)          /* End of file reached */
       break;
  }
  fclose(inputFilePtr); /* Close the file */
  return 0;
}
Il problema è che devo poter scorrere il testo e non posso usare delle API, con la funzione Reader dovrei passare il nome del file e la linea di partenza per la visualizzazione sullo schermo, ed essa aumenta e diminuisce quando premo rispettivamente giu e su!, solo che quando avvio questa funzione mi viene fuori un bel casino, dato che se la stringa è più lunga della finestra me la manda a capo e la conta come un'altra linea!
Qualcuno può darmi una aiuto?