"Thinkinginc++" 72, input and output stream

Fourth chapter input Output stream

Strfiile.cpp

/*** book: "thinkinginc++" * function: input/output stream of a file * time: October 12, 2014 15:15:59* Author: cutter_point*/#include <iostream>//on many platforms <fstream> will automatically include <iostream> but not all # include <fstream> #include ".   /require.h "using namespace Std;int Main () {const int sz=100;   Size of buffer pool char Buf[sz];  Buffer {ifstream in ("Strfile.cpp");//read in file assure (in, "Strfile.cpp");    Determine that the file was opened Ofstream out ("Strfile.txt");        Output file assure (out, "Strfile.txt");    int i=1;   Represents the first row while (In.get (buf, SZ))//reads in SZ-1 characters or encounters ' \ n ' {in.get ();    Remove ' \ n ' because the above is not read ' \ n ', here ' \ n ' read in, but do not handle cout<<buf<<endl;        Endl must be added here, otherwise it will not be wrapped out<<i++<< "\ t:" <<buf<<endl;    }} Ifstream in ("Strfile.txt");    Assure (in, "Strfile.txt");        while (In.getline (buf, SZ)) {char* cp=buf;        while (*CP! = ': ')//In order to remove the preceding ordinal ++cp;  cp+=2;    This is to remove the ":" cout<<cp<<endl; }    return 0;} 

4.6 Locating in the input and output stream

Flag function

Ios::in Open the input file. Using this open mode for Ofstream can make the existing File is not truncated

Ios::out Open the output file.

Ios::app open an output file for append only

Ios::ate open an existing file and point the file pointer to the end of the file Truncate old file if file exists

Ios::trunc If the file exists, truncate the old file

Ios::binary opens the file in binary mode. Open as text by default

Read (unsigned char *buf,int num); write (const unsigned char *buf,int num);

Read () reads num characters from a file into the cache pointed to by buf, and if it is at the end of the file when NUM characters have not been read, you can use the member function int gcount () to get the number of characters actually read, while write () writes NUM characters from the cache pointed to by BUF to the file. It is important to note that the type of cache is unsigned char *, which may sometimes require a type conversion.

* SEEKG () to the input file location, there are two parameters:
* First: Indicates an offset, can be negative, positive means backward, negative indicates forward
* Second: The base address of the offset, which can be:
* Start of Ios::beg input stream
* Ios::cur the current position of the input stream
* End of Ios::end input stream

4.7 string input/output stream

WS refers to Std::ws, which is used to remove spaces.
Like what:

int i;float F;char buf[100];cin >> i >> f;cin >> std::ws;cin.getline (buf, 100);

At run time, you need to enter an integer number, enter a space, and then enter a floating point. You can then enter a number of spaces and finally enter a string.
Cin after reading the integer and floating-point numbers, it continues to read the string you entered and ignores several spaces between the floating-point number and the string.

Ostring.cpp

/*** book: "thinkinginc++" * Function: Output string stream * Time: October 12, 2014 15:17:02* Author: cutter_point*/#include <iostream> #include < Sstream> #include <string>using namespace Std;int main () {    cout<< "Enter an int, a float, a string of strings"    ; int i;    float F;    cin>>i>>f;    cin>>ws;    Remove the space, WS is the STD inside, in order to ignore the space    string stuff;    Getline (cin, stuff);    Get a row of strings    ostringstream os;   String output stream    os<< "integer =" <<i<<endl;    os<< "float =" <<f<<endl;    os<< "string =" <<stuff<<endl;    String Result=os.str ();    cout<<result<<endl;    return 0;}

4.8 Formatting of the input stream

On/OFF flag	Role
Ios::skipws	Skip Spaces
Ios::showbase	Indicates the cardinality of a number when printing an integer value
Ios::showpoint	Show floating point worthy decimal point and truncate 0 of the end of the number
Ios::uppercase	Use uppercase a~f when displaying hexadecimal values, showing the E in the scientific count
Ios::showpos	The plus sign (+) before displaying a positive number
Ios::unitbuf	"Cell buffers". Refresh after each insert

Ios::basefield	Role
Ios::d EC	Decimal
Ios::hex	Hexadecimal
Ios::oct	Octal

Ios::floatfield	Role
Ios::scientific	Display floating-point numbers in scientific notation
Ios::fixed	Display floating-point numbers in a fixed format
"Automatic"	The Precision field indicates the number of digits of all valid digits

Ios::adjustfield	Role
Ios::left	Value left Justified
Ios::right	Align Right
Ios::internal	Front sign left aligned, trailing value right

Function	Role
Int Ios::width ()	Returns the current width. Default is 0
int ios::width (int n)	Sets the width and returns the current width
Int Ios::fill ()	Returns the current padding character, the default is a space
int Ios::fill (int n)	Sets the fill character and returns the preceding character
Int iOS::p recision ()	Returns the current floating-point precision
int iOS::p recision (int n)	Sets the precision of the floating-point number, returning the previous precision.

Format.cpp

/*** book: "thinkinginc++" * Function: about the use of some format domains * Time: October 12, 2014 15:17:35* Author: cutter_point*/#include <iostream> #include  <fstream>using namespace std; #define D (A) t<< #A <<endl;    A//d (a) represents the first execution of the latter, followed by the meaning of a delegate, int main () {Ofstream T ("Format.txt");    D (int i=47);    D (float f=123456789.543235453);    Const char* s= "I ' m cutter_point"; D (T.SETF (IOS::UNITBUF);)//"Cell buffer".    The Radix d (T.SETF (Ios::uppercase | ios::showpos) of the number is indicated when the D (T.SETF (ios::showbase);)//print integer value is refreshed after each insert;)    D (t<<i<<endl;)//default is 10 binary D (T.SETF (Ios::hex, Ios::basefield);)    D (t<<i<<endl;)    D (T.SETF (ios::oct, Ios::basefield);)    D (t<<i<<endl;)    D (T.UNSETF (ios::showbase);)//Print integer value indicating the cardinality of the number D (T.SETF (iOS::d ec, Ios::basefield);)    D (T.SETF (Ios::left, Ios::adjustfield);)//value left justified D (T.fill (' 0 ');)    D (t<< "Fill char:" <<t.fill () <<endl;)    D (t.width);)    t<<i<<endl;    Right-justified D (T.SETF (ios::right, Ios::adjustfield);) D (T.WIdth (;))    t<<i<<endl;    The front sign is left aligned, and the trailing value is right-justified D (T.SETF (ios::internal, Ios::adjustfield);)    D (t.width);)    t<<i<<endl;    D (t<<i<<endl;)    D (T.UNSETF (ios::showpos);)    D (T.SETF (ios::showpoint);)    D (t<< "prec =" <<t.precision () <<endl;)//sets the precision of the floating-point number, returning the previous precision.    D (T.SETF (ios::scientific, Ios::floatfield);)    D (t<<endl<<f<<endl;)    D (T.UNSETF (ios::uppercase);)    D (t<<endl<<f<<endl;)    D (T.SETF (ios::fixed, Ios::floatfield);)//display floating-point number D (t<<f<<endl;) in a fixed format    D (t.precision);)    D (t<< "prec =" <<t.precision () <<endl;)//sets the precision of the floating-point number, returning the previous precision.    D (t<<endl<<f<<endl;)    D (T.SETF (ios::scientific, Ios::floatfield);)    D (t<<endl<<f<<endl;)    D (T.SETF (ios::fixed, Ios::floatfield);)//display floating-point number D (t<<f<<endl;) in a fixed format    D (t.width);)    t<<s<<endl;    D (t.width);)    t<<s<<endl; D (T.SETF (iOs::left, Ios::adjustfield);)    D (t.width);)    t<<s<<endl; return 0;}

4.9 Manipulation operators

Manipulation operators	Role
Showbase	The cardinality (Dec, Oct, or hex) that displays numbers when output shaping number
Noshowbase
Showpos	Show positive sign (+) in front
Noshowpos
Uppercase	Use uppercase a~f to display hexadecimal numbers, using uppercase E in scientific counting numbers
Nouppercase
Showpoint	Displays the decimal point and the trailing 0 of the floating-point number
Noshowpoint
Skipws	Skip spaces in the input
Noskipws
Left	Value left Justified
Right	Right-aligned, padding characters to the left
Internal	Place a fill character between a guide or cardinality indicator and a value
Scientific	Indicates the preferred output format for floating-point numbers
Fixed

4.9 operator operator 4.9.3 utility operator

Create the operator yourself.

Effector.cpp

 

/*** book: "thinkinginc++" * Function: Utility operator * Time: October 12, 2014 15:18:32* Author: cutter_point*/#include <cassert> #include <    limits> #include <sstream> #include <string> #include <iostream>using namespace Std;class fixw{ String Str;public:fixw (const string& s, int width): str (s, 0, width) {} friend ostream& operator<< (o    stream& OS, const fixw& FW) {return os<<fw.str;    }};typedef unsigned long ulong;    Binary output Class bin{ulong N;public:bin (ulong nn) {n=nn;} Friend ostream& operator<< (ostream& os, const bin& b) {const ULONG Ulmax=numeric_limits<ul        Ong>::max ();        ULONG bit=~ (ulmax>>1); while (bit) {os<< (B.N & bit?)            ' 1 ': ' 0 ');        bit>>=1;    } return OS;    }};int Main () {string words= "C + + that does us happy, make us wise";    for (int i=words.size ();------->= 0;)    {Ostringstream s; Output stream s<<fixw (words, i);        ASSERT (s.str () = = Words.substr (0, i));    Cout<<s.str () <<endl;    } ostringstream xs, Ys;    Xs<<bin (0xCAFEBABEUL);    Cout<<xs.str () <<endl;    Ys<<bin (0x76543210ul);    Cout<<ys.str () <<endl; return 0;}

"Thinkinginc++" 72, input and output stream