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This write and read a std::vector to/from a std::stream example demonstrates a basic, yet not a foolproof
way. The program its setup is fine: a std::vector is created, written to file, a new std::vector
is written from that same file and the program tests if the two std::vectors are identical.
The assumptions for this approach to work are:
- Text may not be '<\>'
- Text must not contain any whitespace type
Note that the program will issue a failed assert when one of these assumptions are violated.
See Write and read a std::vector to/from a std::stream: example 2 for a more elaborated version.
Technical facts
Application type(s)
Operating system(s) or programming environment(s)
IDE(s):
Project type:
C++ standard:
Compiler(s):
Libraries used:
STL: GNU ISO C++ Library, version 4.7.2
Qt project file: CppVectorToStreamExample1.pro
QT -= core gui
QMAKE_CXXFLAGS += -std=c++11 -Werror
TARGET = CppVectorToStreamExample1
CONFIG += console
SOURCES += main.cpp
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main.cpp
#include <iostream>
#include <iterator>
#include <cassert>
#include <algorithm>
#include <fstream>
#include <string>
#include <vector>
std::ostream& operator<<(std::ostream& os, const std::vector<std::string>& v)
{
//Check data
#ifndef NDEBUG
std::for_each(v.begin(),v.end(),
[&os](const std::string& s)
{
assert(s != "</>" && "Text must not be '</>'");
assert(std::count(s.begin(),s.end(),' ') == 0 && "Text must not contain spaces");
}
);
#endif
//Write start tag
os << "<>\n";
//Write data
std::for_each(v.begin(),v.end(),
[&os](const std::string& s)
{
os << s << '\n';
}
);
//Write end tag
os << "</>";
return os;
}
std::istream& operator>>(std::istream& is, std::vector<std::string>& v)
{
//Read start tag
{
std::string s; is >> s; assert(s == std::string("<>"));
}
//Read data until end tag
while (1)
{
std::string s;
is >> s;
if (s == std::string("</>")) return is;
v.push_back(s);
}
}
int main()
{
const std::vector<std::string> v(
{
"aahs",
"aals",
"abac",
"abas",
"abba",
"abbe",
"abbs",
"abed",
"abet",
"abid"
}
);
const std::string filename = "tmp.txt";
//Write to file
{
std::ofstream f(filename.c_str());
f << v;
}
//Read from file
{
std::vector<std::string> w;
std::ifstream f(filename.c_str());
f >> w;
if (v != w)
{
std::copy(w.begin(),w.end(),std::ostream_iterator<std::string>(std::cout,"\n"));
}
assert(v == w);
}
}
|
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