How to print the content of a string as "sting literal source" - c++

Question

Suppose s is
a
b
c
const std::string s =
std::cout << R"( s )" << std::endl;
How to std::cout the content of the string in raw literal? I mean the cout return the value in this format: "a\nb\nc".
I need to transform a very large text into a std::string.
I cant use fileread as i need to define its value inside the src.

Answer 1

What you would need to do is to scan the string, and replace all occurrences of the characters you are interested in (such as carriage return, tab, etc) with printable escape sequence and than print this new text.
Here is somewhat crude proof of concept:
std::string escape(std::string_view src) {
std::string ret;
ret.reserve(src.size() * 2); // at worst, the string consists solely of escapable symbols
static constexpr std::array escapable = {std::make_pair('\t', 't'),
std::make_pair('\n', 'n')}; // add more chars as needed, note that the array is sorted
for (const char ch: src) {
std::pair search_pair{ch, ' '};
auto esc_char = std::equal_range(escapable.begin(), escapable.end(), search_pair, [](auto& a, auto& b) { return a.first < b.first; });
if (esc_char.first != escapable.end()) {
ret.push_back('\\');
ret.push_back(esc_char.first->second);
} else {
ret.push_back(ch);
}
}
return ret;
}
Now, you can use it:
const std::string str = "A\nbub\tfuf\n";
std::cout << escape(str) << "\n";
Above snippet prints A\nbub\tfuf\n

Answer 2

You could be interested by the JSON specification.
You could consider serializing your data in JSON format using open source C++ libraries like jsoncpp
You could also consider using some YAML format with the yaml-cpp library
You could be interested by the SWIG tool which generates C++ glue code.
You could consider using binary data formats like XDR.
You should specify (on paper, with a pencil) your data format in EBNF notation and use ANTLR or GNU bison to generate the parser (the printer is easier to code)
The RefPerSys project (an open source symbolic artificial intelligence system, GPLv3+ licensed) is persisting data in textual format. You may borrow some code are re-use it in your application, if you obey to that GPL license.
Look also into Qt or POCO frameworks, but notice that DWORD64 is not a standard C++ type. See this C++ reference and read a recent C++ standard (like n3337 or better).
Consider generating your C++ serializing code
With tools like GNU m4 or GPP (or your own one).
Pitrat's book Artificial Beings: the Conscience of a Conscious Machine (ISBN-13: 978-1848211018) should give you valuable insight and intuitions.

Answer 3

You can load this text file into a std::string like this:
Store the text in your file, e.g. mystring.txt, as a raw string literal in the format R"(raw_characters)":
R"(Run.M128A XmmRegisters[16];
BYTE Reserved4[96];", Run.CONTEXT64 := " DWORD64 P1Home;
DWORD64 P2Home;
...
)"
#include the file into a string:
namespace
{
const std::string mystring =
#include "mystring.txt"
;
}
Your IDE might flag this up as a syntax error, but it isn't. What you're doing is loading the contents of file directly into the string at compile time.
Finally print the string:
std::cout << mystring << std::endl;
Why not just save the escaped version of the string in the file?
Any way, here's a function to 'escape' characters:
#include <iostream>
#include <string>
#include <unordered_map>
std::string replace_all(const std::string &mystring)
{
const std::unordered_map<char, std::string> lookup =
{ {'\n', "\\n"}, {'\t', "\\t"}, {'"', "\\\""} };
std::string new_string;
new_string.reserve(mystring.length() * 2);
for (auto c : mystring)
{
auto it = lookup.find(c);
if (it != lookup.end())
new_string += it->second;
else
new_string += c;
}
return new_string;
}
int main() {
std::string mystring = R"(Run.M128A XmmRegisters[16];
BYTE Reserved4[96];", Run.CONTEXT64 := " DWORD64 P1Home;
DWORD64 P2Home;
DWORD64 P3Home;
DWORD64 P4Home;
DWORD64 P5Home;
DWORD64 P6Home;)";
auto new_string = replace_all(mystring);
std::cout << new_string << std::endl;
return 0;
}
Here's a demo.