http://utf8everywhere.org/
On Fri, Apr 12, 2019 at 7:51 AM x <tam118...@hotmail.com> wrote: > I’m still confused by utf strings. For simplicity, suppose I set up an > sqlite function that takes a single string parameter and I want to scan the > string to count the number of occurrences of a certain character . If I > knew the string was made up entirely of ascii chars I’d do this > > char *c = &sqlite3_value_text(0)[0]; > int count=0; > while (*c) if (*c++ == SearchChar) count++; > > How do I do the same thing if the string param is a utf-8 or utf-16 string > and the SearchChar is a Unicode character? > You'd decide on the common operating mode of your system for 1... there are of course middleware libraries that need to cater to both and consume databases instead of just writing it. > > I’m confused by the fact that Unicode characters are not a fixed number of > bytes so if I do this e.g. > > wchar_t *c = (wchar_t*) sqlite3_value_text(0); > > https://www.sqlite.org/c3ref/value_blob.html const void *sqlite3_value_text16( returns wchar data, converting if nessecary from utf8 if it was stored as utf8. value_text only returns utf8 (char* really, but suffices for storage and retreival of utf8 phrases) for utf8 it would just be matter of matching 1,2,3, or 4 bytes (depending on the codepoint you were matching). does this mean a complete temporary copy of the value of > sqlite3_value_text(0) has to be constructed by the compiler such that all > characters of the newly constructed string are fixed width? If so, I’m just > wanting to check if there’s a way of avoiding this overhead. > > If it is converted, a temporary value is allocated by the library (at runtime, well beyond the compiler), ... > _______________________________________________ > sqlite-users mailing list > sqlite-users@mailinglists.sqlite.org > http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users > _______________________________________________ sqlite-users mailing list sqlite-users@mailinglists.sqlite.org http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users
