#include <Wire.h>
#define BUFFER_SIZE (192)

unsigned char buf[BUFFER_SIZE];

void setup()
{
  Wire.begin(4);                // join i2c bus with address #4
  Wire.onReceive(receiveEvent); // register event
}

void loop()
{
  //Do whatever you need to with buf in here.
  delay(100);
}

// function that executes whenever data is received from master
// this function is registered as an event, see setup()
void receiveEvent(int howMany)
{
  unsigned char i = 0;
  while(Wire.available() && (i < BUFFER_SIZE))
  {
    buf[i++] = Wire.read(); // receive byte
  }
}