C程序設(shè)計教學課件：CHAPTER 12 THE C INPUT OUTPUT CLASS HIERARCHY

1、C+ Programming CHAPTER 12 THE C+ INPUT/OUTPUT CLASS HIERARCHY112.1 Overview12.2 The High-Level Input/Output Classes 12.3 Manipulators12.4 The File Input/Output Classes12.5 The Character Stream Input/Output Classes212.1 OverviewInput and output facilities are not part of C+ language but instead of fu

2、rnished through a class library.In C+ input and output, a central object is the stream, which is a sequence of bytes. There is a common base class for two derived stream classed basic_istream, an input stream class, and basic_ostream, an output stream class.312.1 OverviewThe standard input/output hi

3、erarchios_basebase_iosbasic_istreambasic_ostreambasic_istringstreambasic_iostreambasic_ostringstreambasic_stringstreambasic_fstreambasic_ifstreambasic_ofstream412.1 OverviewSeveral input/output headers and describes their purpose.HeaderPartial DescriptioniosfwdContains forward declarationsiostreamDe

4、clares cin, cout, etc.iosDeclares ios_base and basic_iosstreambufDeclares basic_streambufistreamDeclares basic_istream ostreamDeclares basic_ostreamiostreamDeclares basic_istream and basic_ostreamiomanipDeclares parameterized manipulatorssstreamDeclares basic_stringbuf and the stringstream classesfs

5、treamDeclares basic_filebuf and the fstream classes512.2 The High-Level Input/Output ClassesIn C+, we use the classes basic_istream, basic_ostream, and basic_iostream to get a high-level interface to input and output.HeaderPartial DescriptioniostreamDeclares basic_istream and basic_iostreamostreamDe

6、clares basic_ostreamistreamDeclares basic_istream 612.2 The High-Level Input/Output Classesbasic_istreambasic_istreamcinvalcin reads the stream, without white space, and save it to the val.Example:int a; char c; char ca20;cinacca;712.2 The High-Level Input/Output Classesbasic_istreamExample:#include

7、 void main()int n; cinn;char ch; cinch;float pi; cinpi;char str20;cinstr;coutn=nendl;coutch=chendl;coutpi=piendl;coutstring=str ( signed char);istream & operator (unsigned char);istream & operator (short);istream & operator (unsigned short);istream & operator (int);istream & operator (unsigned int);

8、istream & operator (long);istream & operator (unsigned long);istream & operator (float);istream & operator (double);istream & operator (long double);912.2 The High-Level Input/Output Classesbasic_istreamMethodsA) get( );When get() is invoked, the next character in the stream, white space or not, is

9、returned.Example:int c;while( ( c=cin.get( ) )!=EOF ) coutc;1012.2 The High-Level Input/Output Classesbasic_istreamB) getline( char_type* b, streamsize s, char_type d );b: an array, into which to write characters: an integer value that bounds the number of charactersd: an end-of-line marker1112.2 Th

10、e High-Level Input/Output Classesbasic_istreamMethod getline reads characters until itReaches end-of-fileEncounters an end-of-line markerStores s-1 characters 12Example:#include #include using namespace std;void main (void) char city80; char country80; int i; for (i = 0; i 2; i+) cin.getline(city,80

11、,); cin.get(country,80,n); cout City: city Country: country endl; cin.clear(); cin.ignore( numeric_limits:max(), n ); Input:Beijing,ChinaShanghai,ChinaOutput:City: Beijing Country: ChinaCity: Shanghai Country: China1312.2 The High-Level Input/Output Classesbasic_istreamC) read( char_type* a, streams

12、ize n);Method read reads characters and stores them in the array a until n characters are read or end-of-file occurs.1412.2 The High-Level Input/Output Classesbasic_ostreambasic_ostreamcoutvalcout puts the stream, in val, to the screen.Example:cout“Hello：”123endl;1512.2 The High-Level Input/Output C

13、lassesbasic_ostreamExample:#include void main()float pi=3.14159;coutpi=;coutpi;coutendl;Output:pi=3.141591612.2 The High-Level Input/Output Classesbasic_ostreamOperator Overloadedostream & operator ( signed char);ostream & operator (unsigned char);ostream & operator (short);ostream & operator (unsig

14、ned short);ostream & operator (int);ostream & operator (unsigned int);ostream & operator (long);ostream & operator (unsigned long);ostream & operator (float);ostream & operator (double);ostream & operator (long double);1712.2 The High-Level Input/Output Classesbasic_ostreamMethodsA) put( char_type )

15、;Method put writes the character passed to the output stream.Example:cout.put( c );1812.2 The High-Level Input/Output Classesbasic_ostreamB) write( const char_type* a, streamsize m);Method write writes m characters from the array a to the output stream.1912.2 The High-Level Input/Output Classesbasic

16、_ostreamExample:#include #includevoid main( )char* pc=this is a test!;cout.put(A);cout.put(n);cout.write(pc,strlen(pc); Output:Athis is a test!2012.2 The High-Level Input/Output Classesbasic_iostreambasic_iostreamClass basic_iostream is publicly inherited from both basic_istream and basic_ostream.21

17、12.2 The High-Level Input/Output Classesbasic_iostreamExample:class Complexpublic:Complex( )real=0.0;imag=0.0;Complex(double r)real=r;imag=0.0;Complex(double r, double i)real=r;imag=i;Complex operator + (const Complex& c);Complex operator - (const Complex& c);Complex operator * (const Complex& c);Co

18、mplex operator / (const Complex& c);friend ostream& operator (istream& In, Complex& x);protected:double real, imag;2212.2 The High-Level Input/Output Classesbasic_iostreamostream& operator(ostream& Out, Complex& x)Outx.real+x.imagi(istream& In, Complex& x)Inx.realx.imag;return In;/2312.2 The High-Le

19、vel Input/Output Classesbasic_iostreamvoid main()Complex a(1,2),b(3,4),c;c=a+b;coutc;Output:4+6i2412.3 ManipulatorsA manipulators is a function that either directly or indirectly modifies a stream.HeaderPartial DescriptioniomanipDeclares parameterized manipulators2512.3 ManipulatorsSeveral manipulat

20、ors with arguments are predefined. ManipulatorActs OnPurposesetBase( int n )basic_ostreamSet integer base to n(0 means default)setfill(char_type c)basic_ostreamSet fill character to csetprecision( int n )basic_ostreamSet precision to nsetw( int n )basic_ostreamSet field width to nsetiosflags( mask )

21、ios_baseSet specified format bitsresetiosflags( mask ) ios_baseClear specified format bits2612.3 ManipulatorssetBaseExample:coutsetbase(8) 9endl;Output:112712.3 ManipulatorssetwExample:#include #include using namespace std;void main() double values =1.23,35.36,653.7,4358.24;char *names =Zoot,Jimmy,A

22、l,Stan;for(int i=0;i4;i+)coutsetw(6)namesi setw(10)valuesi endl; Output: Zoot 1.23 Jimmy 35.36 Al 653.7 Stan 4358.246 106 characters2812.3 ManipulatorssetfillExample:#include #include using namespace std; void main() double values =1.23,35.36,653.7,4358.24; for(int i=0; i4; i+) cout.width(10); couts

23、etfill(*)valuesin; Output:*1.23*35.36*653.7*4358.24Fill with *2912.3 Manipulatorssetiosflags and rsetiosflagsExample:#include #include using namespace std; void main() double values=1.23,35.36,653.7,4358.24; char *names=Zoot,Jimmy,Al,Stan; for(int i=0;i4;i+) coutsetiosflags(ios:left) setw(6)namesi r

24、esetiosflags(ios:left) setw(10)valuesi endl;/ flush left/ remove flush leftOutput:Zoot 1.23Jimmy 35.36Al 653.7Stan 4358.2430setprecisionExample:#include #include using namespace std; void main() double values=1.23,35.36,653.7,4358.24; char *names=Zoot,Jimmy,Al,Stan; coutsetiosflags(ios:scientific);

25、for(int i=0;i4;i+) coutsetiosflags(ios:left) setw(6)namesi resetiosflags(ios:left) setw(10)setprecision(1) valuesiopen(filename,iosmode); 3412.4 The File Input/Output Classesbasic_ofstreamExample:#include fstream.h#include iostream.hvoid main()char buf80;ofstream out(out.txt);while (cin.getline(buf,

26、80, ) coutbufendl;outbufopen(filename,iosmode); 3712.4 The File Input/Output Classesbasic_ifstreamExample:ifstream fin( “data.in” );if( !fin )cerr”Cant open data.inn”;Example:ifstream fin;fin.open( “data.in” );3812.4 The File Input/Output Classesbasic_ifstreamExample:#include fstream.h #include iost

27、ream.hvoid main()int line=1;char buf80;ifstream in(in.txt);ofstream out(out.txt);while (in.getline(buf,80) coutline+:bufendl;outbufopen(filename,iosmode); 4112.4 The File Input/Output Classesbasic_fstreamExample:fstream finout( “data.txt” );In this case the file data.txt is for both input and output

28、.42#include /for file streams#include using namespace std;const int MAX = 100; /size of bufferint buffMAX; /buffer for integersint main() /fill buffer with data for(int j=0; jMAX; j+) buffj = j; /(0, 1, 2, .) /create output stream ofstream os(edata.txt, ios:binary); /write to it os.write( (char*)buf

29、f, MAX*sizeof(int) ); os.close(); /must close itWrite data43 for(j=0; jMAX; j+) /erase buffer buffj = 0; /create input stream ifstream is(edata.txt, ios:binary); /read from it is.read(char*)(buff), MAX*sizeof(int) ); for(j=0; jMAX; j+) /check data if( buffj != j ) cerr Data is incorrectn; return 1;

30、cout Data is correctn; return 0; Read data44Output: data.txt ! # $ % & ( ) * + , - . / 0 1 2 3 4 5 6 7 8 9 : ; ? A B C D E F G H I J K L M N O P Q R S T U V W X Y Z _ a b c 4512.4 The File Input/Output ClassesMethodsMethodsbasic_ofstream:1 open2 close3 tellp: Gets the value for the streams put point

31、er.4612.4 The File Input/Output Classesbasic_fstream4 seekp( streampos pos );5 seekp( streamoff off, ios:seek_dir dir );pos:The new position value; streampos is a typedef equivalent to long.off:The new offset value; streamoff is a typedef equivalent to long.dir: The seek direction specified by the e

32、numerated type ios: seek_dir, with values including: ios: beg Seek from the beginning of the stream. ios: cur Seek from the current position in the stream. ios: end Seek from the end of the stream.4712.4 The File Input/Output Classesbasic_fstreambasic_ifstream:1 open2 close3 get4 getline5 read6 tell

33、g: Gets the value for the streams get pointer.4812.4 The File Input/Output Classesbasic_fstream7 seekg(streampos pos)8 seekg(streamoff off, ios:seek_dir dir) pos: The new position value; streampos is a typedef equivalent to long. off: The new offset value; streamoff is a typedef equivalent to long.

34、dir: The seek direction. Must be one of the following enumerators: ios:beg Seek from the beginning of the stream. ios:cur Seek from the current position in the stream. ios:end Seek from the end of the stream.49Example:1#include /for file streams#include using namespace std;class person /class of per

35、sonsprotected:char name80; /persons nameint age; /persons agepublic:void getData() /get persons datacout name;cout age;void showData(void) /display persons datacout n Name: name;cout n Age: age;50int main() char ch; person pers; /create person object fstream file; /create input/output file file.open

36、(GROUP.DAT, ios:app | ios:out | ios:in | ios:binary ); do /data from user to file cout nEnter persons data:; pers.getData(); /get one persons data file.write( reinterpret_cast(&pers), sizeof(pers) ); /write to file cout ch; while(ch=y); /quit on nreinterpret_cast(&pers)?51 file.seekg(0); /reset to s

37、tart of file /read first person file.read( reinterpret_cast(&pers), sizeof(pers) ); while( !file.eof() ) /quit on EOF cout nPerson:; /display person pers.showData(); /read another person file.read( reinterpret_cast(&pers), sizeof(pers) ); cout endl; return 0;52Example:2int main() person pers; /creat

38、e person object ifstream infile; /create input file infile.open(GROUP.DAT, ios:in | ios:binary); /open file infile.seekg(0, ios:end); /go to 0 bytes from end int endposition = infile.tellg(); /find where we are int n = endposition / sizeof(person); /number of persons cout nThere are n persons in file;53 cout n; int position = (n-1) * sizeof(person); /number times size infile.seekg(position); /bytes from start /read one person infile.read( reinterpret_cast(&pers), sizeof(pers) ); pers.showData(); /display the person cout endl; retur