C++核心准则​​SL.str.1：使用std::string管理字符序列

SL.str.1: Use std::string to own character sequences

SL.str.1：使用std::string管理字符序列

Reason（原因）

string correctly handles allocation, ownership, copying, gradual expansion, and offers a variety of useful operations.

string可以正确处理分配，所有权，复制，渐进增长并提供各种有用的操作。

Example（示例）

vector<string> read_until(const string& terminator)
{
    vector<string> res;
    for (string s; cin >> s && s != terminator; ) // read a word
        res.push_back(s);
    return res;
}

Note how >> and != are provided for string (as examples of useful operations) and there are no explicit allocations, deallocations, or range checks (string takes care of those).

（作为有用的操作的示例）注意>>和!=是如何提供给string的，代码中也没有显性的内存分配和释放或者内存检查（string会处理好这些）。

In C++17, we might use string_view as the argument, rather than const string& to allow more flexibility to callers:

在C++17中，我们可以使用string_view类型参数，而不是const string&以便为用户提供更多的灵活性。

vector<string> read_until(string_view terminator)   // C++17
{
    vector<string> res;
    for (string s; cin >> s && s != terminator; ) // read a word
        res.push_back(s);
    return res;
}

Example, bad（反面示例）

Don't use C-style strings for operations that require non-trivial memory management

不要将C风格字符串用于需要一定复杂度的内存管理的操作中。

char* cat(const char* s1, const char* s2)   // beware!
    // return s1 + '.' + s2
{
    int l1 = strlen(s1);
    int l2 = strlen(s2);
    char* p = (char*) malloc(l1 + l2 + 2);
    strcpy(p, s1, l1);
    p[l1] = '.';
    strcpy(p + l1 + 1, s2, l2);
    p[l1 + l2 + 1] = 0;
    return p;
}

Did we get that right? Will the caller remember to free() the returned pointer? Will this code pass a security review?

我们做对了么？调用者会记住释放返回的指针么？这段代码可以通过安全评审么？

Note（注意）

Do not assume that string is slower than lower-level techniques without measurement and remember that not all code is performance critical. Don't optimize prematurely

不要不经测算就假定string就会比低水平技术慢，并且需要明白不是所有的代码都对性能敏感。不要过早优化。

Enforcement（实施建议）

???

原文链接

https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#slstr1-use-stdstring-to-own-character-sequences