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Diffstat (limited to 'include/o3tl/unit_conversion.hxx')
| -rw-r--r-- | include/o3tl/unit_conversion.hxx | 261 |
1 files changed, 261 insertions, 0 deletions
diff --git a/include/o3tl/unit_conversion.hxx b/include/o3tl/unit_conversion.hxx new file mode 100644 index 000000000..67830f0d1 --- /dev/null +++ b/include/o3tl/unit_conversion.hxx @@ -0,0 +1,261 @@ +/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */ +/* + * This file is part of the LibreOffice project. + * + * 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/. + */ + +#pragma once + +#include <o3tl/safeint.hxx> +#include <sal/macros.h> +#include <sal/types.h> + +#include <array> +#include <cassert> +#include <numeric> +#include <utility> +#include <type_traits> + +namespace o3tl +{ +// Length units +enum class Length +{ + mm100 = 0, // 1/100th mm + mm10, // 1/10 mm, corresponds to MapUnit::Map10thMM + mm, // millimeter + cm, // centimeter + m, // meter + km, // kilometer + emu, // English Metric Unit: 1/360000 cm, 1/914400 in + twip, // "Twentieth of a point" aka "dxa": 1/20 pt + pt, // Point: 1/72 in + pc, // Pica: 1/6 in, corresponds to FieldUnit::PICA and MeasureUnit::PICA + in1000, // 1/1000 in, corresponds to MapUnit::Map1000thInch + in100, // 1/100 in, corresponds to MapUnit::Map100thInch + in10, // 1/10 in, corresponds to MapUnit::Map10thInch + in, // inch + ft, // foot + mi, // mile + master, // PPT Master Unit: 1/576 in + px, // "pixel" unit: 15 twip (96 ppi), corresponds to MeasureUnit::PIXEL + ch, // "char" unit: 210 twip (14 px), corresponds to FieldUnit::CHAR + line, // "line" unit: 312 twip, corresponds to FieldUnit::LINE + count, // <== add new units above this last entry + invalid = -1 +}; + +// If other categories of units would be needed (like time), a separate scoped enum +// should be created, respective conversion array prepared in detail namespace, and +// respective md(NewUnit, NewUnit) overload introduced, which would allow using +// o3tl::convert(), o3tl::convertSaturate() and o3tl::getConversionMulDiv() with the +// new category in a type-safe way, without mixing unrelated units. + +namespace detail +{ +// Common utilities + +// A special function to avoid compiler warning comparing signed and unsigned values +template <typename I> constexpr bool isBetween(I n, sal_Int64 min, sal_Int64 max) +{ + assert(max > 0 && min < 0); + if constexpr (std::is_signed_v<I>) + return n >= min && n <= max; + else + return n <= sal_uInt64(max); +} + +// Ensure correct rounding for both positive and negative integers +template <typename I, std::enable_if_t<std::is_integral_v<I>, int> = 0> +constexpr sal_Int64 MulDiv(I n, sal_Int64 m, sal_Int64 d) +{ + assert(m > 0 && d > 0); + assert(isBetween(n, (SAL_MIN_INT64 + d / 2) / m, (SAL_MAX_INT64 - d / 2) / m)); + return (n >= 0 ? (n * m + d / 2) : (n * m - d / 2)) / d; +} +template <typename F, std::enable_if_t<std::is_floating_point_v<F>, int> = 0> +constexpr double MulDiv(F f, sal_Int64 m, sal_Int64 d) +{ + assert(m > 0 && d > 0); + return f * (double(m) / d); +} + +template <typename I, std::enable_if_t<std::is_integral_v<I>, int> = 0> +constexpr sal_Int64 MulDiv(I n, sal_Int64 m, sal_Int64 d, bool& bOverflow, sal_Int64 nDefault) +{ + if (!isBetween(n, (SAL_MIN_INT64 + d / 2) / m, (SAL_MAX_INT64 - d / 2) / m)) + { + bOverflow = true; + return nDefault; + } + bOverflow = false; + return MulDiv(n, m, d); +} + +template <typename I, std::enable_if_t<std::is_integral_v<I>, int> = 0> +constexpr sal_Int64 MulDivSaturate(I n, sal_Int64 m, sal_Int64 d) +{ + if (!isBetween(n, (SAL_MIN_INT64 + d / 2) / m, (SAL_MAX_INT64 - d / 2) / m)) + { + if (m > d && !isBetween(n, SAL_MIN_INT64 / m * d + d / 2, SAL_MAX_INT64 / m * d - d / 2)) + return n > 0 ? SAL_MAX_INT64 : SAL_MIN_INT64; // saturate + return (n >= 0 ? n + d / 2 : n - d / 2) / d * m; // divide before multiplication + } + return MulDiv(n, m, d); +} + +template <class M, class N> constexpr std::common_type_t<M, N> asserting_gcd(M m, N n) +{ + auto ret = std::gcd(m, n); + assert(ret != 0); + return ret; +} + +// Packs integral multiplier and divisor for conversion from one unit to another +struct m_and_d +{ + sal_Int64 m; // multiplier + sal_Int64 d; // divisor + constexpr m_and_d(sal_Int64 _m, sal_Int64 _d) + : m(_m / asserting_gcd(_m, _d)) // make sure to use smallest quotients here because + , d(_d / asserting_gcd(_m, _d)) // they will be multiplied when building final table + { + assert(_m > 0 && _d > 0); + } +}; + +// Resulting static array N x N of all quotients to convert between all units. The +// quotients are minimal to allow largest range of converted numbers without overflow. +// Maybe o3tl::enumarray could be used here, but it's not constexpr yet. +template <int N> constexpr auto prepareMDArray(const m_and_d (&mdBase)[N]) +{ + std::array<std::array<sal_Int64, N>, N> a{}; + for (int i = 0; i < N; ++i) + { + a[i][i] = 1; + for (int j = 0; j < i; ++j) + { + assert(mdBase[i].m < SAL_MAX_INT64 / mdBase[j].d); + assert(mdBase[i].d < SAL_MAX_INT64 / mdBase[j].m); + const sal_Int64 m = mdBase[i].m * mdBase[j].d, d = mdBase[i].d * mdBase[j].m; + const sal_Int64 g = asserting_gcd(m, d); + a[i][j] = m / g; + a[j][i] = d / g; + } + } + return a; +} + +// A generic template used for fundamental arithmetic types +template <typename U> constexpr sal_Int64 md(U i, U /*j*/) { return i; } + +// Length units implementation + +// Array of conversion quotients for mm, used to build final conversion table. Entries +// are { multiplier, divider } to convert respective unit *to* mm. Order of elements +// corresponds to order in o3tl::Length enum (Length::count and Length::invalid omitted). +constexpr m_and_d mdBaseLen[] = { + { 1, 100 }, // mm100 => mm + { 1, 10 }, // mm10 => mm + { 1, 1 }, // mm => mm + { 10, 1 }, // cm => mm + { 1000, 1 }, // m => mm + { 1000000, 1 }, // km => mm + { 1, 36000 }, // emu => mm + { 254, 10 * 1440 }, // twip => mm + { 254, 10 * 72 }, // pt => mm + { 254, 10 * 6 }, // pc => mm + { 254, 10000 }, // in1000 => mm + { 254, 1000 }, // in100 => mm + { 254, 100 }, // in10 => mm + { 254, 10 }, // in => mm + { 254 * 12, 10 }, // ft => mm + { 254 * 12 * 5280, 10 }, // mi => mm + { 254, 10 * 576 }, // master => mm + { 254 * 15, 10 * 1440 }, // px => mm + { 254 * 210, 10 * 1440 }, // ch => mm + { 254 * 312, 10 * 1440 }, // line => mm +}; +static_assert(std::size(mdBaseLen) == static_cast<int>(Length::count), + "mdBaseL must have an entry for each unit in o3tl::Length"); + +// The resulting multipliers and divisors array +constexpr auto aLengthMDArray = prepareMDArray(mdBaseLen); + +// an overload taking Length +constexpr sal_Int64 md(Length i, Length j) +{ + const int nI = static_cast<int>(i), nJ = static_cast<int>(j); + assert(nI >= 0 && o3tl::make_unsigned(nI) < aLengthMDArray.size()); + assert(nJ >= 0 && o3tl::make_unsigned(nJ) < aLengthMDArray.size()); + return aLengthMDArray[nI][nJ]; +} + +// here might go overloads of md() taking other units ... +} + +// Unchecked conversion. Takes a number value, multiplier and divisor +template <typename N> constexpr auto convert(N n, sal_Int64 mul, sal_Int64 div) +{ + return detail::MulDiv(n, mul, div); +} + +// Unchecked conversion. Takes a number value and units defined in this header +template <typename N, typename U> constexpr auto convert(N n, U from, U to) +{ + return convert(n, detail::md(from, to), detail::md(to, from)); +} + +// Convert to twips - for convenience as we do this a lot +template <typename N> constexpr auto toTwips(N number, Length from) +{ + return convert(number, from, Length::twip); +} + +// Returns nDefault if intermediate multiplication overflows sal_Int64 (only for integral types). +// On return, bOverflow indicates if overflow happened. nDefault is returned when overflow occurs. +template <typename N, typename U> +constexpr auto convert(N n, U from, U to, bool& bOverflow, sal_Int64 nDefault = 0) +{ + return detail::MulDiv(n, detail::md(from, to), detail::md(to, from), bOverflow, nDefault); +} + +// Conversion with saturation (only for integral types). For too large input returns SAL_MAX_INT64. +// When intermediate multiplication would overflow, but the end result is in sal_Int64 range, the +// precision is decreased because of inversion of multiplication and division. +template <typename N, typename U> constexpr auto convertSaturate(N n, U from, U to) +{ + return detail::MulDivSaturate(n, detail::md(from, to), detail::md(to, from)); +} + +// Conversion with saturation (only for integral types), optimized for return types smaller than +// sal_Int64. In this case, it's easier to clamp input values to known bounds, than to do some +// preprocessing to handle too large input values, just to clamp the result anyway. Use it like: +// +// sal_Int32 n = convertNarrowing<sal_Int32, o3tl::Length::mm100, o3tl::Length::emu>(m); +template <typename Out, auto from, auto to, typename N, + std::enable_if_t< + std::is_integral_v<N> && std::is_integral_v<Out> && sizeof(Out) < sizeof(sal_Int64), + int> = 0> +constexpr Out convertNarrowing(N n) +{ + constexpr sal_Int64 nMin = convertSaturate(std::numeric_limits<Out>::min(), to, from); + constexpr sal_Int64 nMax = convertSaturate(std::numeric_limits<Out>::max(), to, from); + if (static_cast<sal_Int64>(n) > nMax) + return std::numeric_limits<Out>::max(); + if (static_cast<sal_Int64>(n) < nMin) + return std::numeric_limits<Out>::min(); + return convert(n, from, to); +} + +// Return a pair { multiplier, divisor } for a given conversion +template <typename U> constexpr std::pair<sal_Int64, sal_Int64> getConversionMulDiv(U from, U to) +{ + return { detail::md(from, to), detail::md(to, from) }; +} +} + +/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */ |