#ifndef _fifo_buffer_h_
#define _fifo_buffer_h_

#include "sys/uio.h"
#include "AmThread.h"

class fifo_buffer
{
  unsigned char* data;
  unsigned char* data_end;

  // write at _p_head
  unsigned char* p_head;

  // read from p_tail
  unsigned char* p_tail;

  unsigned int   size;
  unsigned int   free_space;

public:
  fifo_buffer(unsigned int size);
  ~fifo_buffer();

  // returns space occupied in buffer
  unsigned int get_buffered_bytes() {
    return size - free_space;
  }

  // returns space left in buffer
  unsigned int get_free_space() {
    return free_space;
  }

  // write at the head of the buffer
  int write(const void* buf, unsigned int len);
  int writev(const struct iovec *iov, int iovcnt);

  // returns size of linearly readable data
  unsigned int get_read_bs() {
    return (p_tail <= p_head) ?
      (unsigned int)(p_head - p_tail) :
      (unsigned int)(data_end - p_tail);
  }

  // returns the buffer's tail
  void* get_read_ptr() {
    return p_tail;
  }
  
  // moves the tail's pointer by the length passed
  void skip(unsigned int len) {
    p_tail += len;
    if(p_tail >= data_end)
      p_tail = p_tail - data_end + data;
    free_space += len;
  }
};

#endif