boundedbuffer.cc

nachos系统作业 实现线程系统 实现一个电梯模拟 附实验报告

#include "BoundedBuffer.h"

// create a bounded buffer with a limit of 'maxsize' bytes
//-------------------------------------------------------------------------------------------

BoundedBuffer::BoundedBuffer(int maxsize)
{
       buffersize=maxsize;
       readyRead=0;
       readyWrite=buffersize;
       buffer=(void *)malloc(buffersize);
       bufferend=(char *)buffer+buffersize;
       nextin=(char *)buffer;
       nextout=(char *)buffer;
       lock=new Lock("buffer lock"); 
       notreadyRead=new Condition("buffer not ready read cond");			// enforce mutual exclusive access to the table
       notreadyWrite=new Condition("buffer not ready write cond");
}

//-----------------------------------------------------------------------------------------------

BoundedBuffer::~BoundedBuffer()
{  
      delete buffer;
      delete lock;
      delete notreadyRead;
      delete notreadyWrite;   
}

//---------------------------------------------------------------------------------------------     
     // read 'size' bytes from the bounded buffer, storing into 'data'.
     // ('size' may be greater than 'maxsize')
//----------------------------------------------------------------------------------------------

void
BoundedBuffer::Read(void *data, int size)
{ 
    char *p=(char *)data;
    lock->Acquire();
            while(readyRead<size)
                   notreadyRead->Wait(lock);
    DEBUG('t',"enter Read() size is %d \n",size);
            for(int i=0;i<size;i++)
                   {*p++=*nextout++;
                    if(nextout==bufferend)nextout=(char *)buffer;
                    readyRead--;readyWrite++;} 
             notreadyWrite->Signal(lock);
     lock->Release();
}

//--------------------------------------------------------------------------------------------------   
     // write 'size' bytes from 'data' into the bounded buffer.
     // ('size' may be greater than 'maxsize')
//--------------------------------------------------------------------------------------------------

void 
BoundedBuffer::Write(void *data, int size)
{
    char *p=(char *)data;
    lock->Acquire();
            while(readyWrite<size)
                   notreadyWrite->Wait(lock);
    DEBUG('t',"enter Write() size is %d \n",size);
            for(int i=0;i<size;i++)
                   {*nextin++=*p++;
                    if(nextin==bufferend)nextin=(char *)buffer;
                    readyWrite--;readyRead++;}
             notreadyRead->Signal(lock);
     lock->Release();
}

//--------------------------------------------------------------------------------------------------