如何解析带有原始转义序列的字符串？ [英] How to parse a string with raw escape sequences?

问题描述

假设有两个字符串：

string parse(const string& s) {
    // how to write this function?
}

int main() {
    string s1 = R"(hello\n\"this is a string with escape sequences\"\n)";
    string s2 = "hello\n\"this is a string with escape sequences\"\n";
    assert(parse(s1) == s2);
}

我的问题是，如何编写函数 parse （），以使断言成功，除了一些手工代码遍历字符串和检查每一个可能的转义序列？

My question is, how to write the function parse() in order to make the assertion succeed, other than some hand-made code traversing the string and checking against every possible escape sequence? Is there any existing idiom for doing this?

推荐答案

使用正则表达式来实现换码序列的替换可能是最简单的，但如果你坚持这样做，你可以总是将字符串写入文件作为一个有效的C ++程序的一部分打印字符串到文件，然后从文件中读取它。
（这也可以改进工作没有临时文件）

It's probably the easiest to just implement the replacement of escape sequences using a regular expression, but if you insist on doing it without, you can always write the string to a file as part of a valid C++ program that prints the string to a file, then read it from the file. (This can also be improved to work without temp files at all)

#include <iostream>
#include <fstream>
#include <string>
#include <cstdlib>
#include <assert.h>

using std::string;

string parse(const string& s) {
    std::ofstream ftmp("tmpsrc.cpp");
    ftmp << "#include <iostream>\nint main(int argc, char* argv[]){\n";
    ftmp << "  std::cout << \"" << s << "\";\nreturn 0;}\n\n";
    ftmp.close();
    system("g++ -o tmpprint tmpsrc.cpp");
    system("./tmpprint > tmpstr.txt");
    std::ifstream fin("tmpstr.txt",std::ios::in|std::ios::binary);
    fin.seekg(0,std::ios::end);
    int size=fin.tellg();
    fin.seekg(0);
    string res;
    res.resize(size);
    fin.read(&res[0],size);
    fin.close();
    // Add delete of temp files here
    return res;
}

int main() {
    string s1 = R"(hello\n\"this is a string with escape sequences\"\n)";
    string s2 = "hello\n\"this is a string with escape sequences\"\n";
    assert(parse(s1) == s2);
}

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