/*
 * write lines from stdin to stdout in random order
 *
 * updated 2012-12-24 to seed rand using FNV hash of command-line argument
 *
 * R. Perry, Oct. 2002
 */

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

unsigned int hash( unsigned char buf[], int n)
{
  unsigned int h = 2166136261;

  for( int i = 0; i < n; ++i)
  {
    h = 16777619 * h ^ buf[i];
  }

  return h;
}

char *progname;

char **stack = NULL;
size_t size = 0;
size_t count = 0;

void *erealloc( void *q, size_t bytes)
{
  void *p = realloc( q, bytes);

  if( p == NULL)
  {
    fprintf( stderr, "%s: realloc() failed.\n", progname);
    exit(1);
  }

  return p;
}

void push( char *line)
{
  if( count >= size)
  {
    size = 1.5*size + 100;
    stack = erealloc( stack, size*sizeof(char*));
  }

  stack[count] = erealloc( NULL, strlen(line)+1);
  strcpy( stack[count], line);
  ++count;
}

void print( void)
{
  size_t i;

  for( i = 0; i < count; ++i)
    fputs( stack[i], stdout);
}

void randomize( void)
{
  char *t;
  size_t i, j;

  if( count <= 1)
    return;

  for( i = count - 1; i > 0; --i)
  {
    j = (rand()/(RAND_MAX+1.0))*(i+1); /* 0 .. i */

    if( i != j) /* swap */
    {
      t = stack[i];
      stack[i] = stack[j];
      stack[j] = t;
    }
  }
}

int main( int argc, char *argv[])
{
  unsigned seed;
  char line[BUFSIZ];

  progname = argv[0];

  if( argc > 1)
    seed = hash( (unsigned char *) argv[1], strlen(argv[1]));
  else
    seed = time(0);

#if 0
  printf( "%u\n", seed);
#endif

  srand( seed);

  while( fgets( line, BUFSIZ, stdin))
  {
    push( line);
  }

  randomize();

  print();

  return 0;
}