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

uint8_t buf1[BUFFER_SIZE];
uint8_t buf2[BUFFER_SIZE];

uint8_t *readBuf = buf1;
uint8_t *writeBuf = buf2;

volatile bool needsSwap = false;
volatile uint8_t pos = 0;

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.
/* you can access the bytes directly as an array, with the first 96 being readBuf[0] to readBuf[95] and second readBuf[96] to readBuf[191],
 or if you need to pass to a function whateverFunction(readBuf) or with the size whateverFunction(readBuf, 96);
 Then the second 96 bytes are passed like this whateverFunction(readBuf + 96, 96) */

  delay(100); //remove this when you have code in this loop

  //Swap the buffers,
  if(needsSwap){
    //I assume this loop() is fast, so you'll get here before the master does another tranmission?
    uint8_t *temp = writeBuf;
    writeBuf = readBuf;
    readBuf = temp;
    needsSwap = false;
  }
}

// function that executes whenever data is received from master
// this function is registered as an event, see setup()
// this is blocking, so no other code will run while this is receiving
void receiveEvent(int howMany)
{
  while(Wire.available() && (pos < BUFFER_SIZE))
  {
    writeBuf[pos++] = Wire.read(); // receive byte
  }
  if(pos == BUFFER_SIZE){
    pos = 0;
    needsSwap = true;
  }
}