Différences

Ci-dessous, les différences entre deux révisions de la page.

--- lang:cpp:string [2019/02/11 00:16] – Création avec "Split" root
+++ lang:cpp:string [2023/05/29 11:58] (Version actuelle) – [consteval avec std::string_view] : fix lien root
@@ Ligne 1: / Ligne 1: @@
+====wstring====
+''wstring'' est surtout utile pour Windows car toutes les appels de fonctions finissant par ''W'' en ont besoin.
+<code cpp>
+#include <fstream>
+#include <ios>
+#include <codecvt>
+std::wofstream out("file.txt", std::ios_base::out | std::ios_base::app);
+const std::locale utf8_locale = std::locale(std::locale(), new std::codecvt_utf8<wchar_t>());
+out.imbue(utf8_locale);
+// Verify that the file opened correctly
+std::wstring s(L"contenu");
+out << s << std::endl;
+</code>
+[[https://stackoverflow.com/questions/37395399/multiplatform-way-to-write-a-stdwstring-into-a-file-in-c|Multiplatform way to write a std::wstring into a file in C++]] {{ :lang:cpp:string:encoding_-_multiplatform_way_to_write_a_std_wstring_into_a_file_in_c_-_stack_overflow_2019-12-27_20_18_07_.html |Archive du 23/05/2016 le 27/12/2019}}
+  * Conversion entre string et wstring
+Sous windows :
+<code cpp>
+std::wstring s2ws(const std::string& s)
+{
+  int slength = (int)s.length() + 1;
+  int len = MultiByteToWideChar(CP_ACP, 0, s.c_str(), slength, 0, 0);
+  std::wstring r(len, L'\0');
+  MultiByteToWideChar(CP_ACP, 0, s.c_str(), slength, &r[0], len);
+  return r;
+}
+std::string ws2s(const std::wstring& s)
+{
+  int slength = (int)s.length() + 1;
+  int len = WideCharToMultiByte(CP_ACP, 0, s.c_str(), slength, 0, 0, 0, 0);
+  std::string r(len, '\0');
+  WideCharToMultiByte(CP_ACP, 0, s.c_str(), slength, &r[0], len, 0, 0);
+  return r;
+}
+</code>
+[[https://codereview.stackexchange.com/questions/419/converting-between-stdwstring-and-stdstring|Converting between std::wstring and std::string]] {{ :lang:cpp:string:c_-_converting_between_std_wstring_and_std_string_-_code_review_stack_exchange_04_05_2023_14_44_33_.html |Archive du 29/01/2011 le 04/05/2023}}
+====stringstream===
+Le résultat ne va pas être le même si on donne à ''std::stringstream'' un ''int'' ou un ''char''.
+  ss << static_cast<char>(1);
+va donner ''\x1''.
+  ss << static_cast<int>(1);
+va donner ''1''.
+====consteval avec std::string_view====
+Ce n'est pas possible. Il faut travailler avec les ''char*''.
+<code cpp>
+#include <array>
+#include <cstring>
+template <class T, std::size_t N>
+struct decayable_array : std::array<T, N> {
+  constexpr operator const T*() const { return this->data(); }
+};
+template <std::size_t N>
+consteval decayable_array<char, N> reverse(const char (&arr)[N]) {
+  decayable_array<char, N> data{};
+  for (std::size_t i = 0; i < N - 1; ++i) {
+    data[N - i - 2] = arr[i];
+  }
+  return data;
+}
+int main() { return strlen(reverse("abc")); }
+</code>
+<code asm>
+main:
+  mov     eax, 3
+  ret
+</code>
+[[https://godbolt.org/z/b4sY41Gbx|Exemple godbolt]]
 ====Split====
+===string===
 <code cpp>
 std::istringstream f("denmark;sweden;india;us");
@@ Ligne 8: / Ligne 97: @@
 </code>
-[[https://stackoverflow.com/questions/5167625/splitting-a-c-stdstring-using-tokens-e-g|Splitting a C++ std::string using tokens, e.g. “;”]] {{ :lang:cpp:string:splitting_a_c_std_string_using_tokens_e.g._-_stack_overflow.mhtml |Archive du 10/02/2019}}
+[[https://stackoverflow.com/questions/5167625/splitting-a-c-stdstring-using-tokens-e-g|Splitting a C++ std::string using tokens, e.g. “;”]] {{ :lang:cpp:string:splitting_a_c_std_string_using_tokens_e.g._-_stack_overflow_2019-12-27_20_18_56_.html |Archive du 02/03/2011 le 27/12/2019}}
+===string_view===
+<code cpp>
+std::vector<std::string_view>
+splitSV(std::string_view strv, std::string_view delims = " ")
+{
+  std::vector<std::string_view> output;
+  size_t first = 0;
+  while (first < strv.size())
+  {
+    const auto second = strv.find_first_of(delims, first);
+    if (first != second)
+      output.emplace_back(strv.substr(first, second-first));
+    if (second == std::string_view::npos)
+      break;
+    first = second + 1;
+  }
+  return output;
+}
+</code>
+[[https://www.bfilipek.com/2018/07/string-view-perf-followup.html|Speeding Up string_view String Split Implementation]] {{ :lang:cpp:string:bartek_s_coding_blog_speeding_up_string_view_string_split_implementation_2019-12-27_20_19_05_.html |Archive du 30/07/2018 le 27/12/2019}}