libcruft-util/ascii.hpp

/*
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 *
 * Copyright 2016-2019 Danny Robson <danny@nerdcruft.net>
 */

#pragma once

#include "annotation.hpp"
#include "debug/assert.hpp"

#include <array>
#include <cstdint>
#include <stdexcept>


namespace cruft::ascii {
    ///////////////////////////////////////////////////////////////////////////
    /// Returns true if the supplied character is an ASCII digit.
    constexpr inline
    bool
    is_digit (char c) noexcept
    {
        return c >= '0' && c <= '9';
    }

    ///------------------------------------------------------------------------
    /// Converts an ASCII character into a corresponding integer.
    ///
    /// Specifically does not convert multiple characters.
    constexpr inline
    uint8_t
    to_integer (char c)
    {
        return likely (is_digit (c)) ?
              c - '0'
            : throw std::invalid_argument ("character is not a digit");
    }


    ///------------------------------------------------------------------------
    /// Returns true if the supplied character is an upper case letter in the
    /// "C" locale.
    constexpr inline
    bool
    is_upper (char c) noexcept
    {
        return c >= 'A' && c <= 'Z';
    }


    ///------------------------------------------------------------------------
    /// Returns true if the supplied character is a lower case letter in the
    /// "C" locale.
    constexpr inline
    bool
    is_lower (char c) noexcept
    {
        return c >= 'a' && c <= 'z';
    }


    ///------------------------------------------------------------------------
    /// Returns true if the supplied character is an alphabetical character in
    /// the "C" locale.
    constexpr inline
    bool
    is_alpha (char c) noexcept
    {
        return is_lower (c) || is_upper (c);
    }


    ///------------------------------------------------------------------------
    /// Returns true if the supplied ASCII character is a hexadecimal digit.
    constexpr inline
    bool
    is_hex (const char c) noexcept
    {
        switch (c) {
        case '0'...'9': return true;
        case 'a'...'f': return true;
        case 'A'...'F': return true;
        }

        return false;
    }


    ///------------------------------------------------------------------------
    /// Converts a supplied ASCII character from a hexadecimal digit into a
    /// corresponding integer.
    ///
    /// Explicitly does not cover any multi-character case.
    constexpr inline
    uint8_t
    from_hex (char c)
    {
        return c >= '0' && c <= '9' ? (c - '0'     ) :
               c >= 'a' && c <= 'f' ? (c - 'a' + 10) :
               c >= 'A' && c <= 'F' ? (c - 'A' + 10) :
               throw std::invalid_argument ("character is not hexademical");
    }


    ///////////////////////////////////////////////////////////////////////////
    /// Converts a lower case ASCII character into an upper case character.
    ///
    /// The results are undefined if the character isn't a lowercase
    /// alphabetical character in the "C" locale.
    constexpr inline
    char
    to_upper (char c) noexcept
    {
        CHECK (is_lower (c));
        return c - 'a' + 'A';
    }


    ///------------------------------------------------------------------------
    /// Convert an ASCII character into a upper case character if it is lower
    /// case, else return it unchanged.
    ///
    /// If you know the character is always lower case then prefer to_upper.
    constexpr inline
    char
    try_upper (char c) noexcept
    {
        return is_lower (c) ? to_upper (c) : c;
    }


    ///------------------------------------------------------------------------
    /// Converts an upper case ASCII character into a lower case character.
    ///
    /// The results are undefined if the character isn't an uppercase
    /// alphabetical character in the "C" locale.
    constexpr inline
    char
    to_lower (char c) noexcept
    {
        CHECK (is_upper (c));
        return c - 'A' + 'a';
    }


    ///------------------------------------------------------------------------
    /// Convert an ASCII character into a lower case character if it is upper
    /// case, else return it unchanged.
    ///
    /// If you know the character is always upper case then prefer to_lower.
    constexpr inline
    char
    try_lower (char c) noexcept
    {
        return is_upper (c) ? to_lower (c) : c;
    }


    ///////////////////////////////////////////////////////////////////////////
    /// Returns true if the supplied ASCII character is whitespace.
    constexpr inline
    bool
    is_space (char c)
    {
        switch (c) {
        case ' ':
        case '\f':
        case '\n':
        case '\r':
        case '\t':
        case '\v':
            return true;

        default:
            return false;
        }
    }
}


///////////////////////////////////////////////////////////////////////////////
#include <vector>

/// Converts a string of ASCII hex digits into a vector of u08 values.
///
/// The supplied string must have a length that is a multiple of 2.
std::vector<std::uint8_t>
inline
operator""_hex2u08 (const char *str, size_t len)
{
    CHECK_MOD (len, 2);
    std::vector<uint8_t> res (len/2);

    for (size_t i = 0; i < len; i += 2)
        res[i/2] = cruft::ascii::from_hex (str[i]) << 4 | cruft::ascii::from_hex (str[i+1]);
    return res;
};


///////////////////////////////////////////////////////////////////////////////
/// Converts a string of ASCII hex digits into an array of u08 values.
///
/// The supplied string must have a length that is a multiple of 2.
template <typename CharT, CharT ...StrV>
constexpr auto
operator""_hex2array (void)
{
    static_assert (sizeof ...(StrV) % 2 == 0);

    std::array<std::uint8_t,sizeof...(StrV)/2> res {};
    constexpr CharT literal[] = { StrV... };

    for (size_t i = 0; i < res.size (); ++i)
        res[i] = cruft::ascii::from_hex (literal[i*2+0]) << 4 |
                 cruft::ascii::from_hex (literal[i*2+1]);

    return res;
}