Case insensitive std::string.find()

Question

I am using std::string's find() method to test if a string is a substring of another. Now I need case insensitive version of the same thing. For string comparison I can always turn to stricmp() but there doesn't seem to be a stristr().

I have found various answers and most suggest using Boost which is not an option in my case. Additionally, I need to support std::wstring/wchar_t. Any ideas?

Answer 1

You could use std::search with a custom predicate.

#include <locale> #include <iostream> #include <algorithm> using namespace std;  // templated version of my_equal so it could work with both char and wchar_t template<typename charT> struct my_equal {     my_equal( const std::locale& loc ) : loc_(loc) {}     bool operator()(charT ch1, charT ch2) {         return std::toupper(ch1, loc_) == std::toupper(ch2, loc_);     } private:     const std::locale& loc_; };  // find substring (case insensitive) template<typename T> int ci_find_substr( const T& str1, const T& str2, const std::locale& loc = std::locale() ) {     typename T::const_iterator it = std::search( str1.begin(), str1.end(),          str2.begin(), str2.end(), my_equal<typename T::value_type>(loc) );     if ( it != str1.end() ) return it - str1.begin();     else return -1; // not found }  int main(int arc, char *argv[])  {     // string test     std::string str1 = "FIRST HELLO";     std::string str2 = "hello";     int f1 = ci_find_substr( str1, str2 );      // wstring test     std::wstring wstr1 = L"ОПЯТЬ ПРИВЕТ";     std::wstring wstr2 = L"привет";     int f2 = ci_find_substr( wstr1, wstr2 );      return 0; }