ringbuffer.h

C++高级编程这本书所附的源代码

#include <vector>
#include <string>
#include <fstream>

using std::string;
using std::vector;
using std::ostream;

//
// class RingBuffer
//
// Provides a simple debug buffer. The client specifies the number
// of entries in the constructor and adds messages with the addEntry()
// method. Once the number of entries exceeds the number allowed, new
// entries overwrite the oldest entries in the buffer.
//
// The buffer also provides the option to print entries as they
// are added to the buffer. The client can specify an output stream
// in the constructor, and can reset it with the setOutput() method.
// 
// Finally, the buffer supports streaming to an output stream.
//
class RingBuffer
{
 public:
  //
  // Constructs a ring buffer with space for numEntries.
  // Entries are written to *ostr as they are queued.
  //
  RingBuffer(int numEntries = kDefaultNumEntries, ostream* ostr = NULL);
  ~RingBuffer();

  //
  // Adds the string to the ring buffer, possibly overwriting the
  // oldest string in the buffer (if the buffer is full).
  //
  void addEntry(const string& entry);

  //
  // Streams the buffer entries, separated by newlines, to ostr.
  //
  friend ostream& operator<<(ostream& ostr, const RingBuffer& rb);

  //
  // Sets the output stream to which entries are streamed as they are added.
  // Returns the old output stream.
  //
  ostream* setOutput(ostream* newOstr);

 protected:
  vector<string> mEntries;
  ostream* mOstr;
  
  int mNumEntries, mNext;
  bool mWrapped;

  static const int kDefaultNumEntries = 500;

 private:
  // Prevent assignment and pass-by-value
  RingBuffer(const RingBuffer& src);
  RingBuffer& operator=(const RingBuffer& rhs);
};