special glyphs from systemd

tree.c

#include <assert.h>
#include <langinfo.h>
#include <locale.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

char *strv_find(char **l, const char *name);

#define streq(a, b) (strcmp((a), (b)) == 0)

#define STRV_FOREACH(s, l)                      \
            for ((s) = (l); (s) && *(s); (s)++)

#define strv_contains(l, s) (!!strv_find((l), (s)))
#define STRV_MAKE(...) ((char**) ((const char*[]) { __VA_ARGS__, NULL }))
#define STR_IN_SET(x, ...) strv_contains(STRV_MAKE(__VA_ARGS__), x)

typedef enum {
    TREE_VERTICAL,
    TREE_BRANCH,
    TREE_RIGHT,
    TREE_SPACE,
    TRIANGULAR_BULLET,
    BLACK_CIRCLE,
    ARROW,
    MDASH,
    _SPECIAL_GLYPH_MAX
} SpecialGlyph;


char *strv_find(char **l, const char *name) {
        char **i;

        assert(name);

        STRV_FOREACH(i, l)
                if (streq(*i, name))
                        return *i;

        return NULL;
}


bool is_locale_utf8(void) {
        const char *set;
        static int cached_answer = -1;

        /* Note that we default to 'true' here, since today UTF8 is
         * pretty much supported everywhere. */

        if (cached_answer >= 0)
                goto out;

        if (!setlocale(LC_ALL, "")) {
                cached_answer = true;
                goto out;
        }

        set = nl_langinfo(CODESET);
        if (!set) {
                cached_answer = true;
                goto out;
        }

        if (streq(set, "UTF-8")) {
                cached_answer = true;
                goto out;
        }

        /* For LC_CTYPE=="C" return true, because CTYPE is effectly
         * unset and everything can do to UTF-8 nowadays. */
        set = setlocale(LC_CTYPE, NULL);
        if (!set) {
                cached_answer = true;
                goto out;
        }

        /* Check result, but ignore the result if C was set
         * explicitly. */
        cached_answer =
                STR_IN_SET(set, "C", "POSIX") &&
                !getenv("LC_ALL") &&
                !getenv("LC_CTYPE") &&
                !getenv("LANG");

out:
        return (bool) cached_answer;
}


const char *special_glyph(SpecialGlyph code) {
    static const char* const draw_table[2][_SPECIAL_GLYPH_MAX] = {
        /* ASCII fallback */
        [false] = {
            [TREE_VERTICAL]      = "| ",
            [TREE_BRANCH]        = "|-",
            [TREE_RIGHT]         = "`-",
            [TREE_SPACE]         = "  ",
            [TRIANGULAR_BULLET]  = ">",
            [BLACK_CIRCLE]       = "*",
            [ARROW]              = "->",
            [MDASH]              = "-",
        },

        /* UTF-8 */
        [true] = {
            [TREE_VERTICAL]      = "\342\224\202 ",            /* │  */
            [TREE_BRANCH]        = "\342\224\234\342\224\200", /* ├─ */
            [TREE_RIGHT]         = "\342\224\224\342\224\200", /* └─ */
            [TREE_SPACE]         = "  ",                       /*    */
            [TRIANGULAR_BULLET]  = "\342\200\243",             /* ‣ */
            [BLACK_CIRCLE]       = "\342\227\217",             /* ● */
            [ARROW]              = "\342\206\222",             /* → */
            [MDASH]              = "\342\200\223",             /* – */
        },
    };

    return draw_table[is_locale_utf8()][code];
}

int main(void)
{
    printf("%s\n", special_glyph(TREE_BRANCH));
    return 0;
}