library/_str_mod.py

#!/usr/bin/env python3
# Copyright (c) Facebook, Inc. and its affiliates. (http://www.facebook.com)
"""This is an internal module implementing __mod__ formatting for str and bytes"""

from builtins import (
    _float,
    _index,
    _mapping_check,
    _number_check,
    _str_array,
)

from _builtins import (
    _bytes_check,
    _float_check,
    _float_format,
    _float_signbit,
    _int_check,
    _str_array_iadd,
    _str_check,
    _str_len,
    _tuple_check,
    _tuple_getitem,
    _tuple_len,
    _type,
)


_FLAG_LJUST = 1 << 0
_FLAG_ZERO = 1 << 1


def _format_string(result, flags, width, precision, fragment):
    if precision >= 0:
        fragment = fragment[:precision]
    if width <= 0:
        _str_array_iadd(result, fragment)
        return

    padding_len = -1
    padding_len = width - _str_len(fragment)
    if padding_len > 0 and not (flags & _FLAG_LJUST):
        _str_array_iadd(result, " " * padding_len)
        padding_len = 0
    _str_array_iadd(result, fragment)
    if padding_len > 0:
        _str_array_iadd(result, " " * padding_len)


def _format_number(result, flags, width, precision, sign, prefix, fragment):
    if width <= 0 and precision < 0:
        _str_array_iadd(result, sign)
        _str_array_iadd(result, prefix)
        _str_array_iadd(result, fragment)
        return

    # Compute a couple values before assembling the result:
    # - `padding_len` the number of spaces around the number
    #    - _FLAG_LJUST determines whether it is before/after
    #    - We compute it by starting with the full width and subtracting the
    #      length of everything else we are going to emit.
    # - `num_leading_zeros` number of extra zeros to print between prefix and
    #    the number.
    fragment_len = _str_len(fragment)
    padding_len = width - fragment_len - _str_len(sign) - _str_len(prefix)

    num_leading_zeros = 0
    if precision >= 0:
        num_leading_zeros = precision - fragment_len
        if num_leading_zeros > 0:
            padding_len -= num_leading_zeros

    if (flags & _FLAG_ZERO) and not (flags & _FLAG_LJUST):
        # Perform padding by increasing precision instead.
        if padding_len > 0:
            num_leading_zeros += padding_len
        padding_len = 0

    # Compose the result.
    if padding_len > 0 and not (flags & _FLAG_LJUST):
        _str_array_iadd(result, " " * padding_len)
        padding_len = 0
    _str_array_iadd(result, sign)
    _str_array_iadd(result, prefix)
    if num_leading_zeros > 0:
        _str_array_iadd(result, "0" * num_leading_zeros)
    _str_array_iadd(result, fragment)
    if padding_len > 0:
        _str_array_iadd(result, " " * padding_len)


_int_format = int.__format__


class Formatter:
    CATEGORY = None

    @staticmethod
    def cast(x):
        raise NotImplementedError("virtual")

    as_str = as_repr = cast

    def percent_c_not_in_range(self):
        raise NotImplementedError("virtual")

    def percent_c_overflow(self):
        raise NotImplementedError("virtual")

    def percent_c_requires_int_or_char(self):
        raise NotImplementedError("virtual")

    def percent_d_a_number_is_required(self, c, tname):
        raise NotImplementedError("virtual")

    def must_be_real_number(self, float_exception, tname):
        raise NotImplementedError("virtual")

    def not_all_arguments_converted(self):
        return TypeError(
            f"not all arguments converted during {self.CATEGORY} formatting"
        )

    def format(self, string: [str, bytes], args) -> [str, bytes]:  # noqa: C901
        string = self.as_str(string)

        args_dict = None
        if _tuple_check(args):
            args_tuple = args
            args_len = _tuple_len(args_tuple)
        else:
            args_tuple = (args,)
            args_len = 1
        arg_idx = 0

        result = _str_array()
        idx = -1
        begin = 0
        in_specifier = False
        it = str.__iter__(string)
        try:
            while True:
                c = it.__next__()
                idx += 1
                if c is not "%":  # noqa: F632
                    continue

                _str_array_iadd(result, string[begin:idx])

                in_specifier = True
                c = it.__next__()
                idx += 1

                # Escaped % symbol
                if c is "%":  # noqa: F632
                    _str_array_iadd(result, "%")
                    begin = idx + 1
                    in_specifier = False
                    continue

                # Parse named reference.
                if c is "(":  # noqa: F632
                    # Lazily initialize args_dict.
                    if args_dict is None:
                        if (
                            _tuple_check(args)
                            or _str_check(args)
                            or not _mapping_check(args)
                        ):
                            raise TypeError("format requires a mapping")
                        args_dict = args

                    pcount = 1
                    keystart = idx + 1
                    while pcount > 0:
                        c = it.__next__()
                        idx += 1
                        if c is ")":  # noqa: F632
                            pcount -= 1
                        elif c is "(":  # noqa: F632
                            pcount += 1
                    key = string[keystart:idx]

                    # skip over closing ")"
                    c = it.__next__()
                    idx += 1

                    # lookup parameter in dictionary.
                    value = args_dict[self.cast(key)]
                    args_tuple = (value,)
                    args_len = 1
                    arg_idx = 0

                # Parse flags.
                flags = 0
                positive_sign = ""
                use_alt_formatting = False
                while True:
                    if c is "-":  # noqa: F632
                        flags |= _FLAG_LJUST
                    elif c is "+":  # noqa: F632
                        positive_sign = "+"
                    elif c is " ":  # noqa: F632
                        if positive_sign is not "+":  # noqa: F632
                            positive_sign = " "
                    elif c is "#":  # noqa: F632
                        use_alt_formatting = True
                    elif c is "0":  # noqa: F632
                        flags |= _FLAG_ZERO
                    else:
                        break
                    c = it.__next__()
                    idx += 1

                # Parse width.
                width = -1
                if c is "*":  # noqa: F632
                    if arg_idx >= args_len:
                        raise TypeError("not enough arguments for format string")
                    arg = _tuple_getitem(args_tuple, arg_idx)
                    arg_idx += 1
                    if not _int_check(arg):
                        raise TypeError("* wants int")
                    width = arg
                    if width < 0:
                        flags |= _FLAG_LJUST
                        width = -width
                    c = it.__next__()
                    idx += 1
                elif "0" <= c <= "9":
                    width = 0
                    while True:
                        width += ord(c) - ord("0")
                        c = it.__next__()
                        idx += 1
                        if not ("0" <= c <= "9"):
                            break
                        width *= 10

                # Parse precision.
                precision = -1
                if c is ".":  # noqa: F632
                    precision = 0
                    c = it.__next__()
                    idx += 1
                    if c is "*":  # noqa: F632
                        if arg_idx >= args_len:
                            raise TypeError("not enough arguments for format string")
                        arg = _tuple_getitem(args_tuple, arg_idx)
                        arg_idx += 1
                        if not _int_check(arg):
                            raise TypeError("* wants int")
                        precision = max(0, arg)
                        c = it.__next__()
                        idx += 1
                    elif "0" <= c <= "9":
                        while True:
                            precision += ord(c) - ord("0")
                            c = it.__next__()
                            idx += 1
                            if not ("0" <= c <= "9"):
                                break
                            precision *= 10

                # Parse and process format.
                if arg_idx >= args_len:
                    raise TypeError("not enough arguments for format string")
                arg = _tuple_getitem(args_tuple, arg_idx)
                arg_idx += 1

                if c is "s":  # noqa: F632
                    fragment = self.as_str(arg)
                    _format_string(result, flags, width, precision, fragment)
                elif c is "r":  # noqa: F632
                    fragment = self.as_repr(arg)
                    _format_string(result, flags, width, precision, fragment)
                elif c is "a":  # noqa: F632
                    fragment = ascii(arg)
                    _format_string(result, flags, width, precision, fragment)
                elif c is "c":  # noqa: F632
                    if _str_check(arg):
                        if _str_len(arg) != 1:
                            raise self.percent_c_requires_int_or_char()
                        fragment = arg
                    else:
                        try:
                            value = _index(arg)
                        except Exception:
                            raise self.percent_c_requires_int_or_char() from None
                        try:
                            fragment = chr(value)
                        except ValueError:
                            raise self.percent_c_not_in_range() from None
                        except OverflowError:
                            raise self.percent_c_overflow() from None
                        except Exception:
                            raise self.percent_c_requires_int_or_char() from None
                    _format_string(result, flags, width, precision, fragment)
                elif c is "d" or c is "i" or c is "u":  # noqa: F632
                    try:
                        if not _number_check(arg):
                            raise TypeError()
                        value = int(arg)
                    except TypeError:
                        tname = _type(arg).__name__
                        raise self.percent_d_a_number_is_required(c, tname) from None
                    if value < 0:
                        value = -value
                        sign = "-"
                    else:
                        sign = positive_sign
                    fragment = int.__str__(value)
                    _format_number(result, flags, width, precision, sign, "", fragment)
                elif c is "x":  # noqa: F632
                    try:
                        if not _number_check(arg):
                            raise TypeError()
                        value = _index(arg)
                    except TypeError:
                        raise TypeError(
                            f"%{c} format: an integer is required, not {_type(arg).__name__}"
                        ) from None
                    if value < 0:
                        value = -value
                        sign = "-"
                    else:
                        sign = positive_sign
                    prefix = "0x" if use_alt_formatting else ""
                    fragment = _int_format(value, "x")
                    _format_number(
                        result, flags, width, precision, sign, prefix, fragment
                    )
                elif c is "X":  # noqa: F632
                    try:
                        if not _number_check(arg):
                            raise TypeError()
                        value = _index(arg)
                    except TypeError:
                        raise TypeError(
                            f"%{c} format: an integer is required, not {_type(arg).__name__}"
                        ) from None
                    if value < 0:
                        value = -value
                        sign = "-"
                    else:
                        sign = positive_sign
                    prefix = "0X" if use_alt_formatting else ""
                    fragment = _int_format(value, "X")
                    _format_number(
                        result, flags, width, precision, sign, prefix, fragment
                    )
                elif c is "o":  # noqa: F632
                    try:
                        if not _number_check(arg):
                            raise TypeError()
                        value = _index(arg)
                    except TypeError:
                        tname = _type(arg).__name__
                        raise TypeError(
                            f"%o format: an integer is required, not {tname}"
                        ) from None
                    if value < 0:
                        value = -value
                        sign = "-"
                    else:
                        sign = positive_sign
                    prefix = "0o" if use_alt_formatting else ""
                    fragment = _int_format(value, "o")
                    _format_number(
                        result, flags, width, precision, sign, prefix, fragment
                    )
                elif c in "eEfFgG":
                    try:
                        value = _float(arg)
                    except TypeError as float_exception:
                        value = float_exception
                    # TODO(T87283131) This is better handled with exception
                    # chaining, but it currently breaks tests
                    if not _float_check(value):
                        tname = _type(arg).__name__
                        raise self.must_be_real_number(value, tname)
                    if precision < 0:
                        precision = 6
                    # The `value != value` test avoids emitting "-nan".
                    if _float_signbit(value) and not value != value:
                        sign = "-"
                    else:
                        sign = positive_sign
                    fragment = _float_format(
                        value, c, precision, True, False, use_alt_formatting
                    )
                    _format_number(result, flags, width, 0, sign, "", fragment)
                else:
                    raise ValueError(
                        f"unsupported format character '{c}' ({ord(c):#x}) at index {idx}"
                    )

                begin = idx + 1
                in_specifier = False
        except StopIteration:
            # Make sure everyone called `idx += 1` after `it.__next__()`.
            assert idx + 1 == _str_len(string)

        if in_specifier:
            raise ValueError("incomplete format")
        _str_array_iadd(result, string[begin:])

        if arg_idx < args_len and args_dict is None:
            # Lazily check that the user did not specify an args dictionary and if
            # not raise an error:
            if _tuple_check(args) or _str_check(args) or not _mapping_check(args):
                raise self.not_all_arguments_converted()
        return self.cast(result.__str__())


class StringLikeFormatter(Formatter):
    CATEGORY = "string"
    as_str = cast = staticmethod(str)
    as_repr = staticmethod(repr)

    def percent_c_not_in_range(self):
        import sys

        return OverflowError("%c arg not in range({m:#x})".format(m=sys.maxunicode + 1))

    def percent_c_overflow(self):
        return TypeError("%c requires int or char")

    def percent_c_requires_int_or_char(self):
        return TypeError("%c requires int or char")

    def percent_d_a_number_is_required(self, c, tname):
        return TypeError(f"%{c} format: a number is required, not {tname}")

    def must_be_real_number(self, float_exception, tname):
        return float_exception


class BytesLikeFormatter(Formatter):
    CATEGORY = "bytes"

    @staticmethod
    def cast(s):
        if _str_check(s):
            return bytes(s, "utf-8")
        return bytes(s)

    @staticmethod
    def as_str(s):
        try:
            if _bytes_check(s):
                return s.decode("utf-8")
            return bytes(s).decode()
        except TypeError:
            raise TypeError(
                f"%b requires a bytes-like object, or an object that implements __bytes__, not '{_type(s).__name__}'"
            )

    @staticmethod
    def as_repr(arg):
        fragment = repr(arg)
        return "".join(c if c <= "\xff" else f"\\U{ord(c):08x}" for c in fragment)

    def percent_c_not_in_range(self):
        raise OverflowError("%c arg not in range(256)")

    def percent_c_overflow(self):
        return OverflowError("%c arg not in range(256)")

    def percent_c_requires_int_or_char(self):
        return TypeError("%c requires an integer in range(256) or a single byte")

    def percent_d_a_number_is_required(self, c, tname):
        if c == "i":
            c = "d"
        return TypeError(f"%{c} format: a number is required, not {tname}")

    def must_be_real_number(self, float_exception, tname):
        return TypeError(f"float argument required, not {tname}")


str_format = StringLikeFormatter().format
bytes_format = BytesLikeFormatter().format