rng.cpp

一个嵌入式系统的C代码

//***********************************************************************
//  MODULE : Rng - Class Header						*
//  AUTHOR : Ron Chernich						*
//  PURPOSE: Ring buffer body routines for the RCOS system		*
//  HISTORY:								*
//   18-JAN-93	First (MSC/C++ 7.00) version				*
//***********************************************************************


#include "rng.hpp"


#pragma check_stack (off)
/////////////////
// Class Constructor defaults buffer size to 16 entries
//
Rng::Rng (UINT16 length)
{
  size = length;
  head = tail = 0;
  buf = new char[length];
  memset(buf, 0, length);
}

///////////////
// Class destructor
//
Rng::~Rng ()
{
  delete buf;
}

/////////////
// Add an entry to the buffer.	If the head catches the tail, the "new"
// char will over-write the previous one.
//
void Rng::RngPut (char ch)
{
  unsigned short idx = head;

  *(buf+idx) = ch;
  if (++idx >= size)
    idx = 0;
  if (idx != tail)
    head = idx;
}

////////////////
// Get a char from the buffer (provided there is one to get).  The status
// routine should be called first to check for something there.
// RETURNS: next char in buffer (or NULL if no char was ready)
//
char Rng::RngGet (void)
{
  char ch;

  if (head == tail)
    ch = '\0';
  else {
    ch = *(buf+tail);
    if (++tail >= size)
      tail = 0;
  }
  return ch;
}

///////////////////
// Anybody home?
// RETURNS: TRUE  .. we have a char
//	    FALSE .. queue empty
//
BOOL Rng::RngStat (void)
{

  return (BOOL)(head != tail);
}

#pragma check_stack (on)


/************************************ EOF ******************************/