UPPERCASE and lowercase

[sazanof]

I'm only a beginner in C++ programming

Perhaps the question is very stupid, but nevertheless, I can't find how to translate a string into upper or lower case.
toupper() - not work, throws an error
std::uppercase() - std undeclared
on github - no same issues
on this forum - no same questions

How I can use standart libraries to convert char array to uppercase?

[MicroController]

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#include <string>

void makeUpper(std::string& str) {
    for(auto& c : str) {
        c = std::toupper(c);
    }
}

[sazanof]

Thak you!
I tired

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#include <string.h>

and

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#include <string>

with your code

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void makeUpper(std::string& str) {
    for(auto& c : str) {
        c = std::toupper(c);
    }
}

, but if I use

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#include <string>

, I got

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fatal error: string: No such file or directory

I use this code in a component with cMake:

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idf_component_register(SRCS "wifi.c"
                       PRIV_REQUIRES esp_wifi esp_event nvs
                       INCLUDE_DIRS ".")

I Try to add

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string

into PRIV_REQUIRES section, but it triggers an error...
And if I use #include <string.h> then I got this

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error: expected ')' before '::' token
   30 | void makeUpper(std::string& str) {
      |                   ^~
      |                   )

Also I turn on formatter and it changed code like this

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void makeUpper(std::string &str)
{
    for (auto &c : str)
    {
        c = std::toupper(c);
    }
}

with the same error.
I do not understand what I doin wrong.

[sazanof]

Maybe because "string" is CPP, and my file is wifi.c?

[MicroController]

Yes, if you want to use C++ (including std::string) the source file has to be named ".cpp".

[sazanof]

So, I corrected code like this

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void to_upper(char *str, char *out_str)
{
    for (int i = 0; i < strlen(str); i++)
    {
        out_str[i] = toupper(str[i]);
    }
}

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char *text = "this is uppercase string!";
    char out_text[strlen(text)];
    to_upper(text, out_text);
    ESP_LOGI("UPPER", "%s", out_text);

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I (559) UPPER: THIS IS UPPERCASE STRING!

[MicroController]

Great

For better efficiency I suggest a modification, to avoid strlen(str) being evaluated over and over again.

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void to_upper(const char *str, char *out_str)
{
  while(*str != 0) {
    *out_str = toupper(*str);
    ++str;
    ++out_str;
  }
  *out_str = 0;
}

[sazanof]

Got It! Done! Thanks a lot again!