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Code Issues Releases Activity

SERVER-17556: StatusWith move only type support

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This commit is contained in:
Mark Benvenuto 2015-03-11 18:42:52 -04:00
parent e12ee3248d
commit 010b40a018
1 changed files with 59 additions and 27 deletions
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86
src/mongo/base/status_with.h
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@ -29,35 +29,33 @@
#pragma once
#include <boost/static_assert.hpp>
#include <boost/type_traits/is_same.hpp> // TODO replace with std::is_same in C++11
#include <iosfwd>
#include <type_traits>
#include "mongo/base/status.h"
namespace mongo {
/*
* StatusWith is used to return an error or a value
* this is designed to make exception code free cleaner by not needing as many out paramters
* example:
StatusWith<int> fib( int n ) {
if ( n < 0 ) return StatusWith<int>( ErrorCodes::BadValue, "paramter to fib has to be >= 0" );
if ( n <= 1 ) return StatusWith<int>( 1 );
StatusWith<int> a = fib( n - 1 );
StatusWith<int> b = fib( n - 2 );
if ( !a.isOK() ) return a;
if ( !b.isOK() ) return b;
return StatusWith<int>( a.getValue() + b.getValue() );
}
* Note: the value is copied in the current implementation, so should be small (int, int*)
* not a vector
/**
* StatusWith is used to return an error or a value.
* This class is designed to make exception-free code cleaner by not needing as many out
* parameters.
*
* Example:
* StatusWith<int> fib( int n ) {
* if ( n < 0 )
* return StatusWith<int>( ErrorCodes::BadValue, "paramter to fib has to be >= 0" );
* if ( n <= 1 ) return StatusWith<int>( 1 );
* StatusWith<int> a = fib( n - 1 );
* StatusWith<int> b = fib( n - 2 );
* if ( !a.isOK() ) return a;
* if ( !b.isOK() ) return b;
* return StatusWith<int>( a.getValue() + b.getValue() );
* }
*/
template<typename T>
class StatusWith {
BOOST_STATIC_ASSERT(!(boost::is_same<T, Status>::value)); // StatusWith<Status> is banned.
static_assert(!(std::is_same<T, mongo::Status>::value), "StatusWith<Status> is banned.");
public:
/**
@ -70,22 +68,56 @@ namespace mongo {
/**
* for the error case
*/
/*implicit*/ StatusWith( const Status& status )
StatusWith( const Status& status )
: _status( status ) {
// verify(( !status.isOK() ); // TODO
}
/**
* for the OK case
*/
/*implicit*/ StatusWith( const T& t )
: _status( Status::OK() ), _t( t ) {
StatusWith(T t)
: _status(Status::OK()), _t(std::move(t)) {
}
const T& getValue() const { /* verify( isOK() ); */ return _t; } // TODO
const Status& getStatus() const { return _status;}
#if defined(_MSC_VER) && _MSC_VER < 1900
StatusWith(const StatusWith& s)
: _status(s._status), _t(s._t) {
}
bool isOK() const { return _status.isOK(); }
StatusWith(StatusWith&& s)
: _status(std::move(s._status)), _t(std::move(s._t)) {
}
StatusWith& operator=(const StatusWith& other) {
_status = other._status;
_t = other._t;
return *this;
}
StatusWith& operator=(StatusWith&& other) {
_status = std::move(other._status);
_t = std::move(other._t);
return *this;
}
#endif
const T& getValue() const {
// TODO dassert( isOK() );
return _t;
}
T& getValue() {
// TODO dassert( isOK() );
return _t;
}
const Status& getStatus() const {
return _status;
}
bool isOK() const {
return _status.isOK();
}
private:
Status _status;