cpp30.cpp

C++参考书

// Coded by plusir -- Jan.05.2003.
// Standard C++ Bible -- (P340-11-30)

#include <iostream>
#include <string>
#include <cstddef>
#include <new>
using namespace std ;

const int maxnames = 5 ;

class Names
{
	public:
		Names( char *s = NULL )
		{
			if ( s )
				strncpy( name, s, sizeof( name ) ) ;
		}

		void* operator new[] ( size_t ) throw( bad_alloc ) ;
		void operator delete[] ( void* ) throw() ;
		void display( void ) const
		{ cout << name << endl ; }

	private:
		char name[25] ;
		static char pool[] ;
		static short int inuse[maxnames] ;
} ;

char Names::pool[maxnames * sizeof( Names )] ;
short int Names::inuse[maxnames] ;

void* Names::operator new[] ( size_t size ) throw( bad_alloc )
{
	int elements = size / sizeof( Names ) ;
	for ( int p = 0; p < maxnames; ++p ) {
		if ( !inuse[p] ) {
			int i ;
			for ( i = 0; i < elements && p + i < maxnames; ++i )
				if ( inuse[p + i] )
					break ;

			if ( i == elements && p + i < maxnames ) {
				for ( i = 0; i < elements; ++i )
					inuse[p + i] = elements ;
				return pool + p * sizeof( Names ) ;
			}
		}
	}
	throw bad_alloc() ;
}

void Names::operator delete[] ( void *b ) throw()
{
	if ( b != NULL ) {
		int p = ( ( char* )b - pool ) / sizeof( Names ) ;
		int elements = inuse[p] ;
		for ( int i = 0; i < elements; ++i )
			inuse[p + i] = 0 ;
	}
}

int main()
{
	Names* np = new Names[maxnames + 1] ;

	int i ;
	for ( i = 0; i < maxnames; ++i ) {
		cout << endl << "Enter name # " << i + 1 << ": " ;
		char name[25] ;
		cin >> name ;
		*( np + i ) = name ;
	}

	for ( i = 0; i < maxnames; ++i )
		( np + i )->display() ;

	delete [] np ;

	return 0 ;
}