import viperio
from stdarg import arg, va_arg
import t


define TEMP_BUF_SIZE = 68

def get_digit_count(num: uint, base: int) -> int:
    count: int = 0
    if num == 0: return 1
    while num > 0:
        count += 1
        num //= base
    return count

# Return type must be int, matching the CRT `sprintf` and includes/stdio.vp;
# return vsnprintf's write length directly (consistent with the CRT).
export def sprintf(buf: str, rule: str, *args) -> int:
    if buf is None or rule is None: return 0
    return vsnprintf(buf, 0x7FFFFFFF, rule, args)

def vsprintf(buf: str, rule: str, *args) -> int:
    if buf is None or rule is None: return 0
    return vsnprintf(buf, 0x7FFFFFFF, rule, args)

export def snprintf(buf: str, size: sizet, fmt: str, *args) -> int:
    if fmt is None: return 0
    if buf is None or size == 0: return vsnprintf(None, 0, fmt, args)
    ret: int = vsnprintf(buf, size, fmt, args)
    return ret

# Check float special values (IEEE 754): 0=normal, 1=+inf, 2=-inf, 3=nan.
# Do NOT read the bit pattern via `*&fbits = *&fv`: the assignment is silently dropped (fbits stays 0), so this function would always return 0 and inf would spin forever in the float formatting loops. Use pure float semantics instead (NaN: fv != fv; ±inf: fv - fv is NaN, finite gives 0.0).
def _check_special_float(fv: double) -> int:
    if fv != fv: return 3
    diff: double = fv - fv
    if diff != diff:
        if fv < 0.0: return 2
        return 1
    return 0

export def vsnprintf(buf: bytes, size: sizet, fmt: str, ap: str) -> int:
    if fmt is None: return 0
    # Length detection mode: when buf is None, only calculate the formatted length, without actually writing
    # _step=0 makes ptr not advance, repeatedly writing the same dummy byte (harmless), write_count accumulates correctly
    count_mode: int = 0
    _step: int = 1
    _dummy: char = '\0'
    if buf is None or size == 0:
        count_mode = 1
        _step = 0
        buf = &_dummy
        size = 0x7FFFFFFF
    ptr: str = buf
    write_count: int = 0
    temp: [68]char
    temp[0] = '\t'
    while *fmt != 0 and write_count < size - 1:
        if *fmt != 37:
            ptr[0] = *fmt
            write_count += 1
            ptr += _step
            fmt += 1
        else:
            fmt += 1
            if *fmt == 0: break
            width:        int = 0
            pad_zero:     int = 0
            left_align:   int = 0
            show_sign:    int = 0
            space_sign:   int = 0
            alt_form:     int = 0
            precision:    int = -1
            is_long:      int = 0
            is_long_long: int = 0
            is_size:      int = 0
            is_short:     int = 0
            is_char:      int = 0
            while True:
                if *fmt == 45:
                    left_align = 1
                    fmt += 1
                elif *fmt == 48:
                    pad_zero = 1
                    fmt += 1
                elif *fmt == 43:
                    show_sign = 1
                    fmt += 1
                elif *fmt == 32:
                    space_sign = 1
                    fmt += 1
                elif *fmt == 35:
                    alt_form = 1
                    fmt += 1
                else: break
            if show_sign: space_sign = 0
            while *fmt >= 48 and *fmt <= 57:
                width = width * 10 + (*fmt - 48)
                fmt += 1
            if *fmt == 46:
                fmt += 1
                precision = 0
                while *fmt >= 48 and *fmt <= 57:
                    precision = precision * 10 + (*fmt - 48)
                    fmt += 1
            if left_align: pad_zero = 0
            if *fmt == 108:
                is_long = 1
                fmt += 1
                if *fmt == 108:
                    is_long_long = 1
                    is_long = 0
                    fmt += 1
            elif *fmt == 104:
                is_short = 1
                fmt += 1
                if *fmt == 104:
                    is_char = 1
                    is_short = 0
                    fmt += 1
            elif *fmt == 122:
                is_size = 1
                fmt += 1
            elif *fmt == 106:
                is_long_long = 1
                fmt += 1
            elif *fmt == 116:
                is_long = 1
                fmt += 1
            if *fmt == 99:
                if write_count < size - 1:
                    ptr_i: int = va_arg(ap)
                    ptr[0] = char(ptr_i)
                    write_count += 1
                    ptr += _step
                else:
                    ptr_i: int = va_arg(ap)
            elif *fmt == 115:
                s: str = va_arg(ap, t.CPtr)
                if s is None: s = "(None)"
                slen: int = 0
                sc: str = s
                while *sc != 0:
                    slen += 1
                    sc += 1
                if not left_align and width > slen:
                    pad_count: int = width - slen
                    while pad_count > 0 and write_count < size - 1:
                        ptr[0] = 32
                        write_count += 1
                        ptr += _step
                        pad_count -= 1
                while *s != 0 and write_count < size - 1:
                    ptr[0] = *s
                    write_count += 1
                    ptr += _step
                    s += 1
                if left_align and width > slen:
                    pad_count = width - slen
                    while pad_count > 0 and write_count < size - 1:
                        ptr[0] = 32
                        write_count += 1
                        ptr += _step
                        pad_count -= 1
            elif *fmt == 100 or *fmt == 105:
                if is_long_long or is_size or is_long:
                    num_l: int64 = va_arg(ap, int64)
                else:
                    num_l: int64 = int64(va_arg(ap, int))
                if is_char:
                    num_l = int64(char(num_l))
                elif is_short:
                    num_l = int64(short(num_l))
                sign: int = 0
                if num_l < 0:
                    sign = 1
                    if num_l == (-9223372036854775807 - 1):
                        u_num: uint64 = uint64(0x8000000000000000)
                    else:
                        u_num: uint64 = uint64(-num_l)
                else:
                    u_num: uint64 = uint64(num_l)
                    if show_sign: sign = 2
                    elif space_sign: sign = 3
                i: int = 0
                while True:
                    if i >= TEMP_BUF_SIZE - 1: break
                    temp[i] = char(u_num % 10 + 48)
                    i += 1
                    u_num //= 10
                    if u_num <= 0: break
                if sign == 1 and i < TEMP_BUF_SIZE - 1:
                    temp[i] = 45
                    i += 1
                elif sign == 2 and i < TEMP_BUF_SIZE - 1:
                    temp[i] = 43
                    i += 1
                elif sign == 3 and i < TEMP_BUF_SIZE - 1:
                    temp[i] = 32
                    i += 1
                if not left_align and not pad_zero and width > i:
                    pad_count = width - i
                    while pad_count > 0 and write_count < size - 1:
                        ptr[0] = 32
                        write_count += 1
                        ptr += _step
                        pad_count -= 1
                if pad_zero and width > i:
                    pad_count = width - i
                    while pad_count > 0 and write_count < size - 1:
                        ptr[0] = 48
                        write_count += 1
                        ptr += _step
                        pad_count -= 1
                while i > 0 and write_count < size - 1:
                    i -= 1
                    ptr[0] = temp[i]
                    write_count += 1
                    ptr += _step
                if left_align and width > i:
                    pad_count = width - i
                    while pad_count > 0 and write_count < size - 1:
                        ptr[0] = 32
                        write_count += 1
                        ptr += _step
                        pad_count -= 1
            elif *fmt == 117:
                if is_long or is_long_long or is_size:
                    u_num_l: uint64 = va_arg(ap, uint64)
                else:
                    u_num_l: uint64 = uint64(uint(va_arg(ap)))
                i = 0
                while True:
                    if i >= TEMP_BUF_SIZE - 1: break
                    temp[i] = char(u_num_l % 10 + 48)
                    i += 1
                    u_num_l //= 10
                    if u_num_l <= 0: break
                if not left_align and not pad_zero and width > i:
                    pad_count = width - i
                    while pad_count > 0 and write_count < size - 1:
                        ptr[0] = 32
                        write_count += 1
                        ptr += _step
                        pad_count -= 1
                if pad_zero and width > i:
                    pad_count = width - i
                    while pad_count > 0 and write_count < size - 1:
                        ptr[0] = 48
                        write_count += 1
                        ptr += _step
                        pad_count -= 1
                while i > 0 and write_count < size - 1:
                    i -= 1
                    ptr[0] = temp[i]
                    write_count += 1
                    ptr += _step
                if left_align and width > i:
                    pad_count = width - i
                    while pad_count > 0 and write_count < size - 1:
                        ptr[0] = 32
                        write_count += 1
                        ptr += _step
                        pad_count -= 1
            elif *fmt == 120:
                if is_long or is_long_long or is_size:
                    u_num_l: uint64 = va_arg(ap, uint64)
                else:
                    u_num_l: uint64 = uint64(uint(va_arg(ap)))
                is_nonzero: int = 0
                if u_num_l != 0:
                    is_nonzero = 1
                i = 0
                while True:
                    if i >= TEMP_BUF_SIZE - 1: break
                    digit: int = int(u_num_l % 16)
                    if digit < 10:
                        temp[i] = char(digit + 48)
                    else:
                        temp[i] = char(digit - 10 + 97)
                    u_num_l //= 16
                    i += 1
                    if u_num_l <= 0: break
                digit_count: int = i
                prefix_len: int = 0
                if alt_form and is_nonzero:
                    prefix_len = 2
                effective_len: int = digit_count + prefix_len
                if not left_align and not pad_zero and width > effective_len:
                    pad_count = width - effective_len
                    while pad_count > 0 and write_count < size - 1:
                        ptr[0] = 32
                        write_count += 1
                        ptr += _step
                        pad_count -= 1
                if prefix_len > 0:
                    if write_count < size - 1:
                        ptr[0] = 48
                        write_count += 1
                        ptr += _step
                    if write_count < size - 1:
                        ptr[0] = 120
                        write_count += 1
                        ptr += _step
                if pad_zero and width > effective_len:
                    pad_count = width - effective_len
                    while pad_count > 0 and write_count < size - 1:
                        ptr[0] = 48
                        write_count += 1
                        ptr += _step
                        pad_count -= 1
                while i > 0 and write_count < size - 1:
                    i -= 1
                    ptr[0] = temp[i]
                    write_count += 1
                    ptr += _step
                if left_align and width > effective_len:
                    pad_count = width - effective_len
                    while pad_count > 0 and write_count < size - 1:
                        ptr[0] = 32
                        write_count += 1
                        ptr += _step
                        pad_count -= 1
            elif *fmt == 88:
                if is_long or is_long_long or is_size:
                    u_num_l: uint64 = va_arg(ap)
                else:
                    u_num_l: uint64 = uint64(uint(va_arg(ap)))
                is_nonzero = 0
                if u_num_l != 0:
                    is_nonzero = 1
                i = 0
                while True:
                    if i >= TEMP_BUF_SIZE - 1: break
                    digit = int(u_num_l % 16)
                    if digit < 10:
                        temp[i] = char(digit + 48)
                    else:
                        temp[i] = char(digit - 10 + 65)
                    u_num_l //= 16
                    i += 1
                    if u_num_l <= 0: break
                digit_count = i
                prefix_len = 0
                if alt_form and is_nonzero:
                    prefix_len = 2
                effective_len = digit_count + prefix_len
                if not left_align and not pad_zero and width > effective_len:
                    pad_count = width - effective_len
                    while pad_count > 0 and write_count < size - 1:
                        ptr[0] = 32
                        write_count += 1
                        ptr += _step
                        pad_count -= 1
                if prefix_len > 0:
                    if write_count < size - 1:
                        ptr[0] = 48
                        write_count += 1
                        ptr += _step
                    if write_count < size - 1:
                        ptr[0] = 88
                        write_count += 1
                        ptr += _step
                if pad_zero and width > effective_len:
                    pad_count = width - effective_len
                    while pad_count > 0 and write_count < size - 1:
                        ptr[0] = 48
                        write_count += 1
                        ptr += _step
                        pad_count -= 1
                while i > 0 and write_count < size - 1:
                    i -= 1
                    ptr[0] = temp[i]
                    write_count += 1
                    ptr += _step
                if left_align and width > effective_len:
                    pad_count = width - effective_len
                    while pad_count > 0 and write_count < size - 1:
                        ptr[0] = 32
                        write_count += 1
                        ptr += _step
                        pad_count -= 1
            elif *fmt == 111:
                if is_long or is_long_long or is_size:
                    u_num_l: uint64 = va_arg(ap, uint64)
                else:
                    u_num_l: uint64 = uint64(uint(va_arg(ap)))
                if is_char:
                    u_num_l = uint64(char(u_num_l))
                elif is_short:
                    u_num_l = uint64(short(u_num_l))
                i = 0
                if u_num_l == 0 and not alt_form:
                    temp[0] = 48
                    i = 1
                else:
                    while True:
                        if i >= TEMP_BUF_SIZE - 1: break
                        temp[i] = char(u_num_l % 8 + 48)
                        i += 1
                        u_num_l //= 8
                        if u_num_l <= 0: break
                    if alt_form and i < TEMP_BUF_SIZE - 1:
                        temp[i] = 48
                        i += 1
                if not left_align and not pad_zero and width > i:
                    pad_count = width - i
                    while pad_count > 0 and write_count < size - 1:
                        ptr[0] = 32
                        write_count += 1
                        ptr += _step
                        pad_count -= 1
                if pad_zero and width > i:
                    pad_count = width - i
                    while pad_count > 0 and write_count < size - 1:
                        ptr[0] = 48
                        write_count += 1
                        ptr += _step
                        pad_count -= 1
                while i > 0 and write_count < size - 1:
                    i -= 1
                    ptr[0] = temp[i]
                    write_count += 1
                    ptr += _step
                if left_align and width > i:
                    pad_count = width - i
                    while pad_count > 0 and write_count < size - 1:
                        ptr[0] = 32
                        write_count += 1
                        ptr += _step
                        pad_count -= 1
            elif *fmt == 98:
                if is_long or is_long_long or is_size:
                    u_num_l: uint64 = va_arg(ap, uint64)
                else:
                    u_num_l: uint64 = uint64(uint(va_arg(ap)))
                if is_char:
                    u_num_l = uint64(char(u_num_l))
                elif is_short:
                    u_num_l = uint64(short(u_num_l))
                i = 0
                if u_num_l == 0:
                    temp[0] = 48
                    i = 1
                else:
                    while True:
                        if i >= TEMP_BUF_SIZE - 1: break
                        temp[i] = char(u_num_l % 2 + 48)
                        i += 1
                        u_num_l //= 2
                        if u_num_l <= 0: break
                    if alt_form and i < TEMP_BUF_SIZE - 1:
                        temp[i] = 98
                        i += 1
                if not left_align and not pad_zero and width > i:
                    pad_count = width - i
                    while pad_count > 0 and write_count < size - 1:
                        ptr[0] = 32
                        write_count += 1
                        ptr += _step
                        pad_count -= 1
                if pad_zero and width > i:
                    pad_count = width - i
                    while pad_count > 0 and write_count < size - 1:
                        ptr[0] = 48
                        write_count += 1
                        ptr += _step
                        pad_count -= 1
                while i > 0 and write_count < size - 1:
                    i -= 1
                    ptr[0] = temp[i]
                    write_count += 1
                    ptr += _step
                if left_align and width > i:
                    pad_count = width - i
                    while pad_count > 0 and write_count < size - 1:
                        ptr[0] = 32
                        write_count += 1
                        ptr += _step
                        pad_count -= 1
            elif *fmt == 112:
                ptr_val: uint64 = uint64(va_arg(ap, t.CPtr))
                if ptr_val == 0:
                    temp[0] = 40
                    temp[1] = 110
                    temp[2] = 105
                    temp[3] = 108
                    temp[4] = 41
                    i = 5
                else:
                    u_num_l = ptr_val
                    i = 0
                    while True:
                        if i >= TEMP_BUF_SIZE - 1: break
                        digit = int(u_num_l % 16)
                        if digit < 10:
                            temp[i] = char(digit + 48)
                        else:
                            temp[i] = char(digit - 10 + 97)
                        u_num_l //= 16
                        i += 1
                        if u_num_l <= 0: break
                    if i < TEMP_BUF_SIZE - 1:
                        temp[i] = 120
                        i += 1
                    if i < TEMP_BUF_SIZE - 1:
                        temp[i] = 48
                        i += 1
                if not left_align and not pad_zero and width > i:
                    pad_count = width - i
                    while pad_count > 0 and write_count < size - 1:
                        ptr[0] = 32
                        write_count += 1
                        ptr += _step
                        pad_count -= 1
                if pad_zero and width > i:
                    pad_count = width - i
                    while pad_count > 0 and write_count < size - 1:
                        ptr[0] = 48
                        write_count += 1
                        ptr += _step
                        pad_count -= 1
                while i > 0 and write_count < size - 1:
                    i -= 1
                    ptr[0] = temp[i]
                    write_count += 1
                    ptr += _step
                if left_align and width > i:
                    pad_count = width - i
                    while pad_count > 0 and write_count < size - 1:
                        ptr[0] = 32
                        write_count += 1
                        ptr += _step
                        pad_count -= 1
            elif *fmt == 102 or *fmt == 70:
                f_upper: int = 1 if *fmt == 70 else 0
                if precision < 0: precision = 6
                fv: double = va_arg(ap, double)
                f_sp: int = _check_special_float(fv)
                if f_sp != 0:
                    f_sgn_len: int = 0
                    if f_sp == 2:
                        f_sgn_len = 1
                    elif f_sp == 1 and show_sign:
                        f_sgn_len = 1
                    elif f_sp == 1 and space_sign:
                        f_sgn_len = 1
                    f_total_len: int = f_sgn_len + 3
                    if not left_align and width > f_total_len:
                        f_pad: int = width - f_total_len
                        while f_pad > 0 and write_count < size - 1:
                            ptr[0] = 32
                            write_count += 1
                            ptr += _step
                            f_pad -= 1
                    if f_sp == 2:
                        if write_count < size - 1:
                            ptr[0] = 45
                            write_count += 1
                            ptr += _step
                    elif f_sp == 1 and show_sign:
                        if write_count < size - 1:
                            ptr[0] = 43
                            write_count += 1
                            ptr += _step
                    elif f_sp == 1 and space_sign:
                        if write_count < size - 1:
                            ptr[0] = 32
                            write_count += 1
                            ptr += _step
                    fi_c: int = 0
                    while fi_c < 3 and write_count < size - 1:
                        fc: int = 0
                        if f_sp == 3:
                            # nan
                            if fi_c == 0:
                                fc = 110
                            elif fi_c == 1:
                                fc = 97
                            else:
                                fc = 110
                        else:
                            # inf (f_sp==1 +inf or f_sp==2 -inf)
                            if fi_c == 0:
                                fc = 105
                            elif fi_c == 1:
                                fc = 110
                            else:
                                fc = 102
                        if f_upper and fc >= 97 and fc <= 122:
                            fc -= 32
                        ptr[0] = char(fc)
                        write_count += 1
                        ptr += _step
                        fi_c += 1
                    if left_align and width > f_total_len:
                        f_pad = width - f_total_len
                        while f_pad > 0 and write_count < size - 1:
                            ptr[0] = 32
                            write_count += 1
                            ptr += _step
                            f_pad -= 1
                    fmt += 1
                    continue
                if fv < 0.0:
                    if write_count < size - 1:
                        ptr[0] = 45
                        write_count += 1
                        ptr += _step
                    fv = 0.0 - fv
                elif show_sign:
                    if write_count < size - 1:
                        ptr[0] = 43
                        write_count += 1
                        ptr += _step
                elif space_sign:
                    if write_count < size - 1:
                        ptr[0] = 32
                        write_count += 1
                        ptr += _step
                di: int = 0
                work: double = fv
                if work < 1.0:
                    temp[0] = 48
                    di = 1
                else:
                    scale: double = 1.0
                    # Upper-bound guard: inf makes `work >= scale*10.0` always true; finite values need at most 308 iterations
                    scale_guard: int = 0
                    while work >= scale * 10.0 and scale_guard < 400:
                        scale *= 10.0
                        scale_guard += 1
                    while scale >= 1.0 and di < TEMP_BUF_SIZE - 1:
                        d: int = int(work / scale)
                        if d > 9: d = 9
                        temp[di] = char(d + 48)
                        di += 1
                        work = work - double(d) * scale
                        scale /= 10.0
                frac_val: double = work
                for p in range(precision):
                    frac_val *= 10.0
                frac_part: uint64 = uint64(frac_val + 0.5)
                f_total: int = di + (precision + 1 if precision > 0 else 0)
                if not left_align and not pad_zero and width > f_total:
                    pad_count = width - f_total
                    while pad_count > 0 and write_count < size - 1:
                        ptr[0] = 32
                        write_count += 1
                        ptr += _step
                        pad_count -= 1
                if pad_zero and width > f_total:
                    pad_count = width - f_total
                    while pad_count > 0 and write_count < size - 1:
                        ptr[0] = 48
                        write_count += 1
                        ptr += _step
                        pad_count -= 1
                while di > 0 and write_count < size - 1:
                    di -= 1
                    ptr[0] = temp[di]
                    write_count += 1
                    ptr += _step
                if precision > 0:
                    if write_count < size - 1:
                        ptr[0] = 46
                        write_count += 1
                        ptr += _step
                    fi: int = 0
                    while fi < precision and fi < TEMP_BUF_SIZE - 1:
                        temp[fi] = char(frac_part % 10 + 48)
                        fi += 1
                        frac_part //= 10
                    while fi < precision and fi < TEMP_BUF_SIZE - 1:
                        temp[fi] = 48
                        fi += 1
                    while fi > 0 and write_count < size - 1:
                        fi -= 1
                        ptr[0] = temp[fi]
                        write_count += 1
                        ptr += _step
                elif alt_form:
                    if write_count < size - 1:
                        ptr[0] = 46
                        write_count += 1
                        ptr += _step
                if left_align and width > f_total:
                    pad_count = width - f_total
                    while pad_count > 0 and write_count < size - 1:
                        ptr[0] = 32
                        write_count += 1
                        ptr += _step
                        pad_count -= 1
            elif *fmt == 101 or *fmt == 69:
                if precision < 0: precision = 6
                fv: double = va_arg(ap, double)
                e_upper: int = 1 if *fmt == 69 else 0
                e_sp: int = _check_special_float(fv)
                if e_sp != 0:
                    e_sgn_len: int = 0
                    if e_sp == 2:
                        e_sgn_len = 1
                    elif e_sp == 1 and show_sign:
                        e_sgn_len = 1
                    elif e_sp == 1 and space_sign:
                        e_sgn_len = 1
                    e_total_len: int = e_sgn_len + 3
                    if not left_align and width > e_total_len:
                        e_pad: int = width - e_total_len
                        while e_pad > 0 and write_count < size - 1:
                            ptr[0] = 32
                            write_count += 1
                            ptr += _step
                            e_pad -= 1
                    if e_sp == 2:
                        if write_count < size - 1:
                            ptr[0] = 45
                            write_count += 1
                            ptr += _step
                    elif e_sp == 1 and show_sign:
                        if write_count < size - 1:
                            ptr[0] = 43
                            write_count += 1
                            ptr += _step
                    elif e_sp == 1 and space_sign:
                        if write_count < size - 1:
                            ptr[0] = 32
                            write_count += 1
                            ptr += _step
                    ei_c: int = 0
                    while ei_c < 3 and write_count < size - 1:
                        ec: int = 0
                        if e_sp == 3:
                            # nan
                            if ei_c == 0:
                                ec = 110
                            elif ei_c == 1:
                                ec = 97
                            else:
                                ec = 110
                        else:
                            # inf (e_sp==1 +inf or e_sp==2 -inf)
                            if ei_c == 0:
                                ec = 105
                            elif ei_c == 1:
                                ec = 110
                            else:
                                ec = 102
                        if e_upper and ec >= 97 and ec <= 122:
                            ec -= 32
                        ptr[0] = char(ec)
                        write_count += 1
                        ptr += _step
                        ei_c += 1
                    if left_align and width > e_total_len:
                        e_pad = width - e_total_len
                        while e_pad > 0 and write_count < size - 1:
                            ptr[0] = 32
                            write_count += 1
                            ptr += _step
                            e_pad -= 1
                    fmt += 1
                    continue
                if fv < 0.0:
                    if write_count < size - 1:
                        ptr[0] = 45
                        write_count += 1
                        ptr += _step
                    fv = 0.0 - fv
                elif show_sign:
                    if write_count < size - 1:
                        ptr[0] = 43
                        write_count += 1
                        ptr += _step
                elif space_sign:
                    if write_count < size - 1:
                        ptr[0] = 32
                        write_count += 1
                        ptr += _step
                exp10: int = 0
                if fv != 0.0:
                    # Upper-bound guard: inf makes the two loops below always true (inf/10==inf, inf*10==inf)
                    exp_guard: int = 0
                    while fv >= 10.0 and exp_guard < 400:
                        fv /= 10.0
                        exp10 += 1
                        exp_guard += 1
                    exp_guard = 0
                    while fv < 1.0 and exp_guard < 400:
                        fv *= 10.0
                        exp10 -= 1
                        exp_guard += 1
                int_digit: int = int(fv)
                if int_digit > 9: int_digit = 9
                if int_digit < 0: int_digit = 0
                frac_v: double = fv - double(int_digit)
                p: int = 0
                while p < precision:
                    frac_v *= 10.0
                    p += 1
                frac_p: uint64 = uint64(frac_v + 0.5)
                carry: uint64 = 1
                for p in range(precision):
                    carry *= 10
                if frac_p >= carry and carry > 0:
                    frac_p = 0
                    int_digit += 1
                    if int_digit > 9:
                        int_digit = 1
                        exp10 += 1
                e_total: int = 1 + (precision + 1 if precision > 0 else 0) + 4
                if not left_align and not pad_zero and width > e_total:
                    pad_count = width - e_total
                    while pad_count > 0 and write_count < size - 1:
                        ptr[0] = 32
                        write_count += 1
                        ptr += _step
                        pad_count -= 1
                if pad_zero and width > e_total:
                    pad_count = width - e_total
                    while pad_count > 0 and write_count < size - 1:
                        ptr[0] = 48
                        write_count += 1
                        ptr += _step
                        pad_count -= 1
                if write_count < size - 1:
                    ptr[0] = char(int_digit + 48)
                    write_count += 1
                    ptr += _step
                if precision > 0:
                    if write_count < size - 1:
                        ptr[0] = 46
                        write_count += 1
                        ptr += _step
                    fi: int = 0
                    while fi < precision and fi < TEMP_BUF_SIZE - 1:
                        temp[fi] = char(frac_p % 10 + 48)
                        fi += 1
                        frac_p //= 10
                    while fi < precision and fi < TEMP_BUF_SIZE - 1:
                        temp[fi] = 48
                        fi += 1
                    while fi > 0 and write_count < size - 1:
                        fi -= 1
                        ptr[0] = temp[fi]
                        write_count += 1
                        ptr += _step
                elif alt_form:
                    if write_count < size - 1:
                        ptr[0] = 46
                        write_count += 1
                        ptr += _step
                if write_count < size - 1:
                    ptr[0] = 101 if e_upper == 0 else 69
                    write_count += 1
                    ptr += _step
                if write_count < size - 1:
                    ptr[0] = 45 if exp10 < 0 else 43
                    write_count += 1
                    ptr += _step
                exp_abs: uint64 = uint64(exp10) if exp10 >= 0 else uint64(0 - exp10)
                ei: int = 0
                if exp_abs == 0:
                    temp[0] = 48
                    temp[1] = 48
                    ei = 2
                else:
                    while exp_abs > 0 and ei < TEMP_BUF_SIZE - 1:
                        temp[ei] = char(exp_abs % 10 + 48)
                        ei += 1
                        exp_abs //= 10
                    while ei < 2:
                        temp[ei] = 48
                        ei += 1
                while ei > 0 and write_count < size - 1:
                    ei -= 1
                    ptr[0] = temp[ei]
                    write_count += 1
                    ptr += _step
                if left_align and width > e_total:
                    pad_count = width - e_total
                    while pad_count > 0 and write_count < size - 1:
                        ptr[0] = 32
                        write_count += 1
                        ptr += _step
                        pad_count -= 1
            elif *fmt == 103 or *fmt == 71:
                if precision < 0: precision = 6
                if precision == 0: precision = 1
                fv: double = va_arg(ap, double)
                g_upper: int = 1 if *fmt == 71 else 0
                g_sp: int = _check_special_float(fv)
                if g_sp != 0:
                    g_sgn_len: int = 0
                    if g_sp == 2:
                        g_sgn_len = 1
                    elif g_sp == 1 and show_sign:
                        g_sgn_len = 1
                    elif g_sp == 1 and space_sign:
                        g_sgn_len = 1
                    g_total_len: int = g_sgn_len + 3
                    if not left_align and width > g_total_len:
                        g_pad: int = width - g_total_len
                        while g_pad > 0 and write_count < size - 1:
                            ptr[0] = 32
                            write_count += 1
                            ptr += _step
                            g_pad -= 1
                    if g_sp == 2:
                        if write_count < size - 1:
                            ptr[0] = 45
                            write_count += 1
                            ptr += _step
                    elif g_sp == 1 and show_sign:
                        if write_count < size - 1:
                            ptr[0] = 43
                            write_count += 1
                            ptr += _step
                    elif g_sp == 1 and space_sign:
                        if write_count < size - 1:
                            ptr[0] = 32
                            write_count += 1
                            ptr += _step
                    gi_c: int = 0
                    while gi_c < 3 and write_count < size - 1:
                        gc: int = 0
                        if g_sp == 3:
                            # nan
                            if gi_c == 0:
                                gc = 110
                            elif gi_c == 1:
                                gc = 97
                            else:
                                gc = 110
                        else:
                            # inf (g_sp==1 +inf or g_sp==2 -inf)
                            if gi_c == 0:
                                gc = 105
                            elif gi_c == 1:
                                gc = 110
                            else:
                                gc = 102
                        if g_upper and gc >= 97 and gc <= 122:
                            gc -= 32
                        ptr[0] = char(gc)
                        write_count += 1
                        ptr += _step
                        gi_c += 1
                    if left_align and width > g_total_len:
                        g_pad = width - g_total_len
                        while g_pad > 0 and write_count < size - 1:
                            ptr[0] = 32
                            write_count += 1
                            ptr += _step
                            g_pad -= 1
                    fmt += 1
                    continue
                if fv < 0.0:
                    if write_count < size - 1:
                        ptr[0] = 45
                        write_count += 1
                        ptr += _step
                    fv = 0.0 - fv
                elif show_sign:
                    if write_count < size - 1:
                        ptr[0] = 43
                        write_count += 1
                        ptr += _step
                elif space_sign:
                    if write_count < size - 1:
                        ptr[0] = 32
                        write_count += 1
                        ptr += _step
                fv_orig: double = fv
                exp10: int = 0
                if fv != 0.0:
                    # Upper-bound guard: this loop is where it hangs (inf makes fv>=10.0 always true, inf/10==inf)
                    exp_guard: int = 0
                    while fv >= 10.0 and exp_guard < 400:
                        fv /= 10.0
                        exp10 += 1
                        exp_guard += 1
                    exp_guard = 0
                    while fv < 1.0 and exp_guard < 400:
                        fv *= 10.0
                        exp10 -= 1
                        exp_guard += 1
                g_use_e: int = 0
                if exp10 < -4 or exp10 >= precision:
                    g_use_e = 1
                g_len: int = 0
                if g_use_e:
                    int_digit: int = int(fv)
                    if int_digit > 9: int_digit = 9
                    if int_digit < 0: int_digit = 0
                    frac_v: double = fv - double(int_digit)
                    prec_e: int = precision - 1
                    p: int = 0
                    while p < prec_e:
                        frac_v *= 10.0
                        p += 1
                    frac_p: uint64 = uint64(frac_v + 0.5)
                    carry: uint64 = 1
                    for p in range(prec_e):
                        carry *= 10
                    if frac_p >= carry and carry > 0:
                        frac_p = 0
                        int_digit += 1
                        if int_digit > 9:
                            int_digit = 1
                            exp10 += 1
                    temp[0] = char(int_digit + 48)
                    g_len = 1
                    if prec_e > 0:
                        temp[1] = 46
                        g_len = 2
                        # Store fraction digits in reverse order (ones place at g_len+prec_e-1) so temp is already forward-ordered.
                        # The original swap-reverse loop fails in TPV output (digits not reversed, e.g. 456->654); reverse storage matches %f's output and avoids the three-variable swap.
                        fi: int = 0
                        fp_inv: uint64 = frac_p
                        fp_idx: int = g_len + prec_e - 1
                        while fi < prec_e and fp_idx < TEMP_BUF_SIZE - 1:
                            temp[fp_idx] = char(fp_inv % 10 + 48)
                            fp_idx -= 1
                            fp_inv //= 10
                            fi += 1
                        g_len += prec_e
                else:
                    prec_f: int = precision - 1 - exp10
                    if prec_f < 0: prec_f = 0
                    work: double = fv_orig
                    if work < 1.0:
                        temp[0] = 48
                        g_len = 1
                    else:
                        scale: double = 1.0
                        # Upper-bound guard: inf makes `work >= scale*10.0` always true; finite values need at most 308 iterations
                        scale_guard: int = 0
                        while work >= scale * 10.0 and scale_guard < 400:
                            scale *= 10.0
                            scale_guard += 1
                        while scale >= 1.0 and g_len < TEMP_BUF_SIZE - 1:
                            d: int = int(work / scale)
                            if d > 9: d = 9
                            temp[g_len] = char(d + 48)
                            g_len += 1
                            work = work - double(d) * scale
                            scale /= 10.0
                    if prec_f > 0 and g_len < TEMP_BUF_SIZE - 1:
                        temp[g_len] = 46
                        g_len += 1
                        frac_val: double = work
                        for p in range(prec_f):
                            frac_val *= 10.0
                        frac_part: uint64 = uint64(frac_val + 0.5)
                        # Store decimal digits in reverse order (ones place goes to g_len prec_f-1), temp is directly in forward order.
                        # The original swap-reverse loop doesn't work in TPV compiled output (decimal digits aren't reversed, e.g., 456->654),
                        # Change to reverse storage, consistent with %f's reverse output, avoiding three-variable swapping.
                        fi = 0
                        fp_inv: uint64 = frac_part
                        fp_idx: int = g_len + prec_f - 1
                        while fi < prec_f and fp_idx < TEMP_BUF_SIZE - 1:
                            temp[fp_idx] = char(fp_inv % 10 + 48)
                            fp_idx -= 1
                            fp_inv //= 10
                            fi += 1
                        g_len += prec_f
                if not alt_form and g_len > 0:
                    while g_len > 0:
                        if temp[g_len - 1] == 48:
                            g_len -= 1
                        else:
                            break
                    if g_len > 0 and temp[g_len - 1] == 46:
                        g_len -= 1
                g_total: int = g_len
                if g_use_e: g_total = g_len + 4
                if not left_align and not pad_zero and width > g_total:
                    pad_count = width - g_total
                    while pad_count > 0 and write_count < size - 1:
                        ptr[0] = 32
                        write_count += 1
                        ptr += _step
                        pad_count -= 1
                if pad_zero and width > g_total:
                    pad_count = width - g_total
                    while pad_count > 0 and write_count < size - 1:
                        ptr[0] = 48
                        write_count += 1
                        ptr += _step
                        pad_count -= 1
                gi: int = 0
                while gi < g_len and write_count < size - 1:
                    ptr[0] = temp[gi]
                    write_count += 1
                    ptr += _step
                    gi += 1
                if g_use_e:
                    if write_count < size - 1:
                        ptr[0] = 101 if g_upper == 0 else 69
                        write_count += 1
                        ptr += _step
                    if write_count < size - 1:
                        ptr[0] = 45 if exp10 < 0 else 43
                        write_count += 1
                        ptr += _step
                    exp_abs: uint64 = uint64(exp10) if exp10 >= 0 else uint64(0 - exp10)
                    ei: int = 0
                    if exp_abs == 0:
                        temp[0] = 48
                        temp[1] = 48
                        ei = 2
                    else:
                        while exp_abs > 0 and ei < TEMP_BUF_SIZE - 1:
                            temp[ei] = char(exp_abs % 10 + 48)
                            ei += 1
                            exp_abs //= 10
                        while ei < 2:
                            temp[ei] = 48
                            ei += 1
                    while ei > 0 and write_count < size - 1:
                        ei -= 1
                        ptr[0] = temp[ei]
                        write_count += 1
                        ptr += _step
                if left_align and width > g_total:
                    pad_count = width - g_total
                    while pad_count > 0 and write_count < size - 1:
                        ptr[0] = 32
                        write_count += 1
                        ptr += _step
                        pad_count -= 1
            elif *fmt == 97 or *fmt == 65:
                a_upper: int = 1 if *fmt == 65 else 0
                fv: double = va_arg(ap, double)
                a_sp: int = _check_special_float(fv)
                if a_sp != 0:
                    a_sgn_len: int = 0
                    if a_sp == 2:
                        a_sgn_len = 1
                    elif a_sp == 1 and show_sign:
                        a_sgn_len = 1
                    elif a_sp == 1 and space_sign:
                        a_sgn_len = 1
                    a_total_len: int = a_sgn_len + 3
                    if not left_align and width > a_total_len:
                        a_pad: int = width - a_total_len
                        while a_pad > 0 and write_count < size - 1:
                            ptr[0] = 32
                            write_count += 1
                            ptr += _step
                            a_pad -= 1
                    if a_sp == 2:
                        if write_count < size - 1:
                            ptr[0] = 45
                            write_count += 1
                            ptr += _step
                    elif a_sp == 1 and show_sign:
                        if write_count < size - 1:
                            ptr[0] = 43
                            write_count += 1
                            ptr += _step
                    elif a_sp == 1 and space_sign:
                        if write_count < size - 1:
                            ptr[0] = 32
                            write_count += 1
                            ptr += _step
                    ai_c: int = 0
                    while ai_c < 3 and write_count < size - 1:
                        ac: int = 0
                        if a_sp == 3:
                            # nan
                            if ai_c == 0:
                                ac = 110
                            elif ai_c == 1:
                                ac = 97
                            else:
                                ac = 110
                        else:
                            # inf (a_sp==1 +inf or a_sp==2 -inf)
                            if ai_c == 0:
                                ac = 105
                            elif ai_c == 1:
                                ac = 110
                            else:
                                ac = 102
                        if a_upper and ac >= 97 and ac <= 122:
                            ac -= 32
                        ptr[0] = char(ac)
                        write_count += 1
                        ptr += _step
                        ai_c += 1
                    if left_align and width > a_total_len:
                        a_pad = width - a_total_len
                        while a_pad > 0 and write_count < size - 1:
                            ptr[0] = 32
                            write_count += 1
                            ptr += _step
                            a_pad -= 1
                    fmt += 1
                    continue
                fbits: uint64 = 0
                *&fbits = *&fv
                a_neg: int = 1 if (fbits >> 63) != 0 else 0
                a_exp: int = int((fbits >> 52) & 0x7FF)
                a_frac: uint64 = fbits & 0x000FFFFFFFFFFFFF
                a_leading: int = 0
                a_binexp: int = 0
                if a_exp == 0:
                    a_leading = 0
                    if a_frac == 0:
                        a_binexp = 0
                    else:
                        a_binexp = -1022
                else:
                    a_leading = 1
                    a_binexp = a_exp - 1023
                a_prec: int = precision
                if a_prec < 0:
                    a_prec = 13
                if a_prec > 50:
                    a_prec = 50
                a_hi: int = 0
                while a_hi < 13 and a_hi < a_prec:
                    a_digit: int = int((a_frac >> (48 - 4 * a_hi)) & 0xF)
                    if a_digit < 10:
                        temp[a_hi] = char(a_digit + 48)
                    else:
                        if a_upper:
                            temp[a_hi] = char(a_digit - 10 + 65)
                        else:
                            temp[a_hi] = char(a_digit - 10 + 97)
                    a_hi += 1
                while a_hi < a_prec:
                    temp[a_hi] = 48
                    a_hi += 1
                a_hd_count: int = a_prec
                if precision < 0:
                    while a_hd_count > 0 and temp[a_hd_count - 1] == 48:
                        a_hd_count -= 1
                a_has_dot: int = 0
                if a_hd_count > 0:
                    a_has_dot = 1
                elif alt_form:
                    a_has_dot = 1
                a_eb: int = a_binexp
                a_esign: int = 0
                if a_binexp < 0:
                    a_esign = 1
                    a_eb = -a_binexp
                a_ei: int = 0
                if a_eb == 0:
                    temp[60] = 48
                    a_ei = 1
                else:
                    while a_eb > 0 and a_ei < 7:
                        temp[60 + a_ei] = char(a_eb % 10 + 48)
                        a_ei += 1
                        a_eb //= 10
                a_ecount: int = a_ei
                a_sign_len: int = 0
                if a_neg:
                    a_sign_len = 1
                elif show_sign:
                    a_sign_len = 1
                elif space_sign:
                    a_sign_len = 1
                a_content_len: int = a_sign_len + 2 + 1 + a_has_dot + a_hd_count + 1 + 1 + a_ecount
                if not left_align and not pad_zero and width > a_content_len:
                    a_pad = width - a_content_len
                    while a_pad > 0 and write_count < size - 1:
                        ptr[0] = 32
                        write_count += 1
                        ptr += _step
                        a_pad -= 1
                if a_neg:
                    if write_count < size - 1:
                        ptr[0] = 45
                        write_count += 1
                        ptr += _step
                elif show_sign:
                    if write_count < size - 1:
                        ptr[0] = 43
                        write_count += 1
                        ptr += _step
                elif space_sign:
                    if write_count < size - 1:
                        ptr[0] = 32
                        write_count += 1
                        ptr += _step
                if pad_zero and width > a_content_len:
                    a_pad = width - a_content_len
                    while a_pad > 0 and write_count < size - 1:
                        ptr[0] = 48
                        write_count += 1
                        ptr += _step
                        a_pad -= 1
                if write_count < size - 1:
                    ptr[0] = 48
                    write_count += 1
                    ptr += _step
                if write_count < size - 1:
                    if a_upper:
                        ptr[0] = 88
                    else:
                        ptr[0] = 120
                    write_count += 1
                    ptr += _step
                if write_count < size - 1:
                    ptr[0] = char(a_leading + 48)
                    write_count += 1
                    ptr += _step
                if a_has_dot:
                    if write_count < size - 1:
                        ptr[0] = 46
                        write_count += 1
                        ptr += _step
                    a_hj: int = 0
                    while a_hj < a_hd_count and write_count < size - 1:
                        ptr[0] = temp[a_hj]
                        write_count += 1
                        ptr += _step
                        a_hj += 1
                if write_count < size - 1:
                    if a_upper:
                        ptr[0] = 80
                    else:
                        ptr[0] = 112
                    write_count += 1
                    ptr += _step
                if write_count < size - 1:
                    if a_esign:
                        ptr[0] = 45
                    else:
                        ptr[0] = 43
                    write_count += 1
                    ptr += _step
                a_ek: int = a_ecount
                while a_ek > 0 and write_count < size - 1:
                    a_ek -= 1
                    ptr[0] = temp[60 + a_ek]
                    write_count += 1
                    ptr += _step
                if left_align and width > a_content_len:
                    a_pad = width - a_content_len
                    while a_pad > 0 and write_count < size - 1:
                        ptr[0] = 32
                        write_count += 1
                        ptr += _step
                        a_pad -= 1
            elif *fmt == 110:
                if is_long_long or is_long:
                    np: int64* = va_arg(ap, int64*)
                    if np != None:
                        np[0] = int64(write_count)
                elif is_short:
                    sp: short* = va_arg(ap, short*)
                    if sp != None:
                        sp[0] = short(write_count)
                elif is_char:
                    cp: str = va_arg(ap, str)
                    if cp != None:
                        cp[0] = char(write_count)
                else:
                    ip: int* = va_arg(ap, int*)
                    if ip != None:
                        ip[0] = write_count
            elif *fmt == 37:
                if write_count < size - 1:
                    ptr[0] = 37
                    write_count += 1
                    ptr += _step
            else:
                if write_count < size - 1:
                    ptr[0] = *fmt
                    write_count += 1
                    ptr += _step
            fmt += 1
    ptr[0] = 0
    return write_count