os-k/kaleid/libc/sprintf.c

//----------------------------------------------------------------------------//
//                           GNU GPL OS/K                                     //
//                                                                            //
//  Desc:       *s*printf() family                                            //
//                                                                            //
//                                                                            //
//  Copyright © 2018-2019 The OS/K Team                                       //
//                                                                            //
//  This file is part of OS/K.                                                //
//                                                                            //
//  OS/K is free software: you can redistribute it and/or modify              //
//  it under the terms of the GNU General Public License as published by      //
//  the Free Software Foundation, either version 3 of the License, or         //
//  any later version.                                                        //
//                                                                            //
//  OS/K is distributed in the hope that it will be useful,                   //
//  but WITHOUT ANY WARRANTY//without even the implied warranty of            //
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the             //
//  GNU General Public License for more details.                              //
//                                                                            //
//  You should have received a copy of the GNU General Public License         //
//  along with OS/K.  If not, see <https://www.gnu.org/licenses/>.            //
//----------------------------------------------------------------------------//

//
// TODO integer modifiers
//

#include <kalbase.h>

//
// Format str according to fmt using ellipsed arguments
//
size_t sprintf(char *str, const char *fmt, ...)
{
    int ret;
    va_list ap;

    va_start(ap, fmt);
    ret = vsnprintf(str, SIZE_T_MAX, fmt, ap);
    va_end(ap);

    return ret;
}

size_t vsprintf(char *str, const char *fmt, va_list ap)
{
    return vsnprintf(str, SIZE_T_MAX, fmt, ap);
}

//
// (v)sprintf() but with a size limit: no more than n bytes are written in str
// Always null-terminate str
//
size_t snprintf(char *str, size_t n, const char *fmt, ...)
{
    int ret;
    va_list ap;

    va_start(ap, fmt);
    ret = vsnprintf(str, n, fmt, ap);
    va_end(ap);

    return ret;
}

// Size of the buffer is for convertions
#define CONVBUF 64

size_t vsnprintf(char *str, size_t n, const char *fmt, va_list ap)
{
    size_t ret = 0;
    bool lflag = 0, hflag = 0, hhflag = 0, altflag = 0;

    int base;
    char mod;
    char convbuf[CONVBUF] = { 0 };

    char c, *s;
    int d;
    uint u;

    assert(str && fmt);

    if (n == 0) return 0;

    // For aesthetic reasons...
    n--;

    // Go through the format string
    while (*fmt && ret < n) {

        // Regular character
        if (*fmt != '%') {
            *str++ = *fmt++;
            ret++;
            continue;
        }

        // Found a '%'
        while (1) {
            mod = *++fmt;

            if (mod == '%') {
                *str++ = '%';
                ret++;
                break;
            }

            if (mod == '#') {
                altflag = 1;
                continue;
            }

            if (mod == 'l' || mod == 'z' || mod == 't') {
                // 'll'/'z'/'t' aliased to 'l'
                lflag = 1;
                continue;
            }

            if (mod == 'h') {
                if (hflag) hhflag = 1;
                else hflag = 1;
                continue;
            }

            if (mod == 'c') {
                c = (char)va_arg(ap, int);
                *str++ = c;
                ret++;
                break;
            }

            if (mod == 's') {
                s = va_arg(ap, char *);

                while (*s && ret < n) {
                    *str++ = *s++;
                    ret++;
                }

                break;
            }

            if (mod == 'i') {
                mod = 'd';
                goto numeric;
            }

            if (mod == 'p') {
                mod = 'x';
                lflag = 1;
                altflag = 1;
                goto numeric;
            }

            if (mod == 'd' || mod == 'u' || mod == 'b' ||
                mod == 'o' || mod == 'x' || mod == 'X') {

                // Label to avoid some useless tests
                numeric:

                if (altflag && mod != 'd' && mod != 'u') {
                    // #d / #u is undefined behaviour

                    *str++ = '0';
                    if (++ret >= n) break;

                    if (mod != 'o') {
                        *str++ = mod;
                        ret++;
                    }
                }

                // "%d" is a special snowflake, deal with it separately
                if (mod == 'd') {
                    if (lflag) {
                        ltoa(va_arg(ap, long), convbuf, 10);
                    }

                    else {
                        d = va_arg(ap, int);
                        if (hhflag) d &= 0xff;          // char-ify
                        else if (hflag) d &= 0xffff;    // short-ify
                        itoa(d, convbuf, 10);
                    }
                }

                // All unsigned mods
                else {
                    base = (mod == 'u' ? 10 : (mod == 'b' ? 2 : (mod == 'o' ? 8 : 16)));

                    // Every other mod here is unsigned
                    if (lflag) {
                        ultoa(va_arg(ap, ulong), convbuf, base);
                    }

                    else {
                        u = va_arg(ap, uint);
                        if (hhflag) u &= 0xff;          // char-ify
                        else if (hflag) u &= 0xffff;    // short-ify
                        utoa(u, convbuf, base);
                    }

                    // "abcdef" => "ABCDEF"
                    if (mod == 'X') {
                        // Re-use s as an iterator for convbuf
                        s = convbuf;
                        while (*s) {
                            if (islower(*s))
                                *s = toupper(*s);
                            s++;
                        }
                    }
                }

                s = convbuf;
                // Convertions happened, now we write into str
                while (*s && ret < n) {
                    *str++ = *s++;
                    ret++;
                }

                // We're done dealing with this modifier
                break;
            }

            // Unknown/unsupported modifier :|
            *str++ = mod;
            ret++;
            break;
        }

        // We fallthrough here from the "while (1)"
        lflag = hflag = hhflag = altflag = 0;
        fmt++;
    }

    // Null-terminate no matter what
    *str = 0;

    return ret + 1;
}