150 lines
5.1 KiB
C++
150 lines
5.1 KiB
C++
/*
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/.
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*
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* Copyright 2019 Danny Robson <danny@nerdcruft.net>
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*/
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#include "parse/time.hpp"
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#include "parse/value.hpp"
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#include "../ascii.hpp"
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#include <chrono>
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// CXX#20: Define these ratios that aren't currently in all our
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// implementations of the stdlib.
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using days = std::chrono::duration<std::int_fast32_t, std::ratio<86400>>;
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using weeks = std::chrono::duration<std::int_fast32_t, std::ratio<604800>>;
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using months = std::chrono::duration<std::int_fast32_t, std::ratio<2629746>>;
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using years = std::chrono::duration<std::int_fast32_t, std::ratio<31556952>>;
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///////////////////////////////////////////////////////////////////////////////
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/// Shorthand for converting an arbitrary duration to nanoseconds.
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template <typename DurationT>
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std::chrono::nanoseconds to_ns (DurationT val)
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{
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return std::chrono::duration_cast<std::chrono::nanoseconds> (val);
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}
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///////////////////////////////////////////////////////////////////////////////
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enum plural_t {
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PLURAL, SINGULAR
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};
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///----------------------------------------------------------------------------
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/// Try to consume a prefix of a string view, optionally allowing for
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/// pluralisation.
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///
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/// If the prefix is detected the provided view is modified to point
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/// immediately past the prefix, and the value true is returned. Else, the view
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/// is untouched and false is returned.
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///
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/// \tparam _N The number of characters in the null-terminated prefix.
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/// \tparam N The number of displayable characters in the prefix.
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/// \param str The view to be checked for the prefix.
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/// \param prefix The prefix we are checking for.
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/// \param plural Whether to (optionall) perform pluralisation on the prefix.
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/// \return True IFF the prefix was found and the view was updated.
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template <std::size_t _N, std::size_t N = _N - 1>
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static bool
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try_consume_prefix (
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cruft::view<char const*> &str,
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char const (&prefix)[_N],
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plural_t plural = SINGULAR)
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{
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static_assert (N > 0);
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// Ensure both sequences have the same prefix
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if (str.size () < N)
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return false;
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for (size_t i = 0; i < N; ++i)
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if (str[i] != prefix[i])
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return false;
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// Eat the prefix into a temporary
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auto res = str.consume (N);
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// Each the plural suffix if we support one
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if (plural == PLURAL && res.size () >= 1 && res[0] == 's')
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res = res.consume (1);
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// If, after the above, we are empty or we have space then we have been
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// successful...
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if (res.empty () || cruft::ascii::is_space (str[0])) {
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str = res;
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return true;
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}
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// ... otherwise we probably have a trailing unprocessed suffix;
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// eg, 's' with a trailing 'econds'
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return false;
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}
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///////////////////////////////////////////////////////////////////////////////
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cruft::expected<std::chrono::nanoseconds, std::errc>
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cruft::parse::duration::consume (cruft::view<char const*> &remain)
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{
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auto const count = value<std::intmax_t> (remain);
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if (remain.empty ())
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return to_ns (std::chrono::seconds (count));
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while (remain[0] == ' ') {
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remain = remain.consume (1);
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if (remain.empty ())
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return to_ns (std::chrono::seconds (count));
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}
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if (try_consume_prefix (remain, "ns")) return std::chrono::nanoseconds (count);
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if (try_consume_prefix (remain, "us")) return to_ns (std::chrono::microseconds (count));
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if (try_consume_prefix (remain, "ms")) return to_ns (std::chrono::milliseconds (count));
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if (try_consume_prefix (remain, "s")) return to_ns (std::chrono::seconds (count));
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if (try_consume_prefix (remain, "m")) return to_ns (std::chrono::minutes (count));
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if (try_consume_prefix (remain, "h")) return to_ns (std::chrono::hours (count));
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if (try_consume_prefix (remain, "second", PLURAL))
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return to_ns (std::chrono::seconds (count));
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if (try_consume_prefix (remain, "minute", PLURAL))
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return to_ns (std::chrono::minutes (count));
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if (try_consume_prefix (remain, "hour", PLURAL))
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return to_ns (std::chrono::hours (count));
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if (try_consume_prefix (remain, "day", PLURAL))
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return to_ns (days (count));
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if (try_consume_prefix (remain, "week", PLURAL))
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return to_ns (weeks (count));
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if (try_consume_prefix (remain, "month", PLURAL))
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return to_ns (months (count));
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if (try_consume_prefix (remain, "year", PLURAL))
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return to_ns (years (count));
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return cruft::unexpected (std::errc::invalid_argument);
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}
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//-----------------------------------------------------------------------------
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cruft::expected<std::chrono::nanoseconds, std::errc>
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cruft::parse::duration::from (cruft::view<char const*> const &str)
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{
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auto remain = str;
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// Try to parse from the temporary view.
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auto res = ::cruft::parse::duration::consume (remain);
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if (!res)
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return res;
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// Ensure it was totally consumed.
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if (!remain.empty ())
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return cruft::unexpected (std::errc::invalid_argument);
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return res;
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}
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