icuSources/i18n/number_scientific.cpp

   1 // © 2017 and later: Unicode, Inc. and others.
   2 // License & terms of use: http://www.unicode.org/copyright.html
   3
   4 #include "unicode/utypes.h"
   5
   6 #if !UCONFIG_NO_FORMATTING
   7
   8 #include <cstdlib>
   9 #include "number_scientific.h"
  10 #include "number_utils.h"
  11 #include "number_stringbuilder.h"
  12 #include "unicode/unum.h"
  13 #include "number_microprops.h"
  14
  15 using namespace icu;
  16 using namespace icu::number;
  17 using namespace icu::number::impl;
  18
  19 // NOTE: The object lifecycle of ScientificModifier and ScientificHandler differ greatly in Java and C++.
  20 //
  21 // During formatting, we need to provide an object with state (the exponent) as the inner modifier.
  22 //
  23 // In Java, where the priority is put on reducing object creations, the unsafe code path re-uses the
  24 // ScientificHandler as a ScientificModifier, and the safe code path pre-computes 25 ScientificModifier
  25 // instances.  This scheme reduces the number of object creations by 1 in both safe and unsafe.
  26 //
  27 // In C++, MicroProps provides a pre-allocated ScientificModifier, and ScientificHandler simply populates
  28 // the state (the exponent) into that ScientificModifier. There is no difference between safe and unsafe.
  29
  30 ScientificModifier::ScientificModifier() : fExponent(0), fHandler(nullptr) {}
  31
  32 void ScientificModifier::set(int32_t exponent, const ScientificHandler *handler) {
  33     // ScientificModifier should be set only once.
  34     U_ASSERT(fHandler == nullptr);
  35     fExponent = exponent;
  36     fHandler = handler;
  37 }
  38
  39 int32_t ScientificModifier::apply(NumberStringBuilder &output, int32_t /*leftIndex*/, int32_t rightIndex,
  40                                   UErrorCode &status) const {
  41     // FIXME: Localized exponent separator location.
  42     int i = rightIndex;
  43     // Append the exponent separator and sign
  44     i += output.insert(
  45             i,
  46             fHandler->fSymbols->getSymbol(DecimalFormatSymbols::ENumberFormatSymbol::kExponentialSymbol),
  47             UNUM_EXPONENT_SYMBOL_FIELD,
  48             status);
  49     if (fExponent < 0 && fHandler->fSettings.fExponentSignDisplay != UNUM_SIGN_NEVER) {
  50         i += output.insert(
  51                 i,
  52                 fHandler->fSymbols
  53                         ->getSymbol(DecimalFormatSymbols::ENumberFormatSymbol::kMinusSignSymbol),
  54                 UNUM_EXPONENT_SIGN_FIELD,
  55                 status);
  56     } else if (fExponent >= 0 && fHandler->fSettings.fExponentSignDisplay == UNUM_SIGN_ALWAYS) {
  57         i += output.insert(
  58                 i,
  59                 fHandler->fSymbols
  60                         ->getSymbol(DecimalFormatSymbols::ENumberFormatSymbol::kPlusSignSymbol),
  61                 UNUM_EXPONENT_SIGN_FIELD,
  62                 status);
  63     }
  64     // Append the exponent digits (using a simple inline algorithm)
  65     int32_t disp = std::abs(fExponent);
  66     for (int j = 0; j < fHandler->fSettings.fMinExponentDigits || disp > 0; j++, disp /= 10) {
  67         auto d = static_cast<int8_t>(disp % 10);
  68         i += utils::insertDigitFromSymbols(
  69                 output,
  70                 i - j,
  71                 d,
  72                 *fHandler->fSymbols,
  73                 UNUM_EXPONENT_FIELD,
  74                 status);
  75     }
  76     return i - rightIndex;
  77 }
  78
  79 int32_t ScientificModifier::getPrefixLength(UErrorCode &status) const {
  80     (void)status;
  81     // TODO: Localized exponent separator location.
  82     return 0;
  83 }
  84
  85 int32_t ScientificModifier::getCodePointCount(UErrorCode &status) const {
  86     (void)status;
  87     // This method is not used for strong modifiers.
  88     U_ASSERT(false);
  89     return 0;
  90 }
  91
  92 bool ScientificModifier::isStrong() const {
  93     // Scientific is always strong
  94     return true;
  95 }
  96
  97 // Note: Visual Studio does not compile this function without full name space. Why?
  98 icu::number::impl::ScientificHandler::ScientificHandler(const Notation *notation, const DecimalFormatSymbols *symbols,
  99         const MicroPropsGenerator *parent) :
 100         fSettings(notation->fUnion.scientific), fSymbols(symbols), fParent(parent) {}
 101
 102 void ScientificHandler::processQuantity(DecimalQuantity &quantity, MicroProps &micros,
 103                                         UErrorCode &status) const {
 104     fParent->processQuantity(quantity, micros, status);
 105     if (U_FAILURE(status)) { return; }
 106
 107     // Treat zero as if it had magnitude 0
 108     int32_t exponent;
 109     if (quantity.isZero()) {
 110         if (fSettings.fRequireMinInt && micros.rounder.isSignificantDigits()) {
 111             // Show "00.000E0" on pattern "00.000E0"
 112             micros.rounder.apply(quantity, fSettings.fEngineeringInterval, status);
 113             exponent = 0;
 114         } else {
 115             micros.rounder.apply(quantity, status);
 116             exponent = 0;
 117         }
 118     } else {
 119         exponent = -micros.rounder.chooseMultiplierAndApply(quantity, *this, status);
 120     }
 121
 122     // Use MicroProps's helper ScientificModifier and save it as the modInner.
 123     ScientificModifier &mod = micros.helpers.scientificModifier;
 124     mod.set(exponent, this);
 125     micros.modInner = &mod;
 126
 127     // We already performed rounding. Do not perform it again.
 128     micros.rounder = RoundingImpl::passThrough();
 129 }
 130
 131 int32_t ScientificHandler::getMultiplier(int32_t magnitude) const {
 132     int32_t interval = fSettings.fEngineeringInterval;
 133     int32_t digitsShown;
 134     if (fSettings.fRequireMinInt) {
 135         // For patterns like "000.00E0" and ".00E0"
 136         digitsShown = interval;
 137     } else if (interval <= 1) {
 138         // For patterns like "0.00E0" and "@@@E0"
 139         digitsShown = 1;
 140     } else {
 141         // For patterns like "##0.00"
 142         digitsShown = ((magnitude % interval + interval) % interval) + 1;
 143     }
 144     return digitsShown - magnitude - 1;
 145 }
 146
 147 #endif /* #if !UCONFIG_NO_FORMATTING */