Thread: Splitting stream of bytes into block of array.

Also, a bug in the code you posted. You're overrunning the array boundaries:

Code:

for(col =0; col <6  ; col++) {

But your array is only big enough for 4 columns...

Hmm, if you don't mind me thinking out loud, here's some quickie pseudocode for what it seems like you want:

Code:

typedef char page[4][4];

page *book = NULL;
int ch;
int n = 0;

while ( ( ch = getchar() ) != EOF ) {
  page *new_book;
  int i, j;

  ++n;
  new_book = realloc ( book, n );

  if ( new_book == NULL )
    break;

  book = new_book;

  for ( i = 0; i < 4; i++ ) {
    for ( j = 0; j < 4; j++ ) {
      if ( ch == EOF || ch == '\n' )
        goto next_page;

      book[n - 1][i][j] = ch;
      ch = getchar();
    }
  }

next_page:
  ;
}

Of course, you would probably want to keep track of how many characters are in each page.

This could work too:

Code:

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

int main(void)
{
  char (*array)[4][4] = NULL;
  int n_arrays = 0;
  int row = 0, col = 0;
  int ch;
  int i;
  unsigned long total = 0;

  while((ch = getchar()) != '\n' && ch != EOF)
  {
    if(!row && !col)
    {
      array = realloc(array, sizeof(*array) * (n_arrays + 1));
      n_arrays++;
    }

    array[n_arrays - 1][row][col] = ch;
    total++;

    if(++col == 4)
    {
      col = 0;
      if(++row == 4)
        row = 0;
    }
  }

  row = col = i = 0;
  while(total--)
  {
    printf("%c ", array[i][row][col++]);
    if(col == 4)
    {
      col = 0;
      putchar('\n');

      if(++row == 4)
      {
        row = 0;
        i++;
        putchar('\n');
      }
    }
  }

  free(array);
  putchar('\n');

  return 0;
}

My output:

Code:

itsme@dreams:~/C$ ./4x4
This sentence is more than 32 characters long.
T h i s
  s e n
t e n c
e   i s

  m o r
e   t h
a n   3
2   c h

a r a c
t e r s
  l o n
g .
itsme@dreams:~/C$

> However, if i wish to enhance this function by letting the user to enter any arbitrary number of characters
Use fgets() to read the line(s).
Then call another function to pack 16 chars at a time into a 4x4 array.

You could also do repeated [scanf("%.16s")] calls, and check for newlines or other end-of-line terminators of your choosing.

Originally Posted by jafet

You could also do repeated [scanf("%.16s")] calls, and check for newlines or other end-of-line terminators of your choosing.

Being whitespace delimited, this is a step down from previous recommendations, even if there wasn't UB in the format.