com.ibm.icu.impl.units.SingleUnitImpl Maven / Gradle / Ivy
// © 2020 and later: Unicode, Inc. and others.
// License & terms of use: http://www.unicode.org/copyright.html
package com.ibm.icu.impl.units;
import com.ibm.icu.util.MeasureUnit;
// TODO: revisit documentation in this file. E.g. we don't do dimensionless
// units in Java? We use null instead.
/**
* A class representing a single unit (optional SI or binary prefix, and dimensionality).
*/
public class SingleUnitImpl {
/**
* Simple unit index, unique for every simple unit, -1 for the dimensionless
* unit. This is an index into a string list in unit.txt {ConversionUnits}.
*
* The default value is -1, meaning the dimensionless unit:
* isDimensionless() will return true, until index is changed.
*/
private int index = -1;
/**
* SimpleUnit is the simplest form of a Unit. For example, for "square-millimeter", the simple unit would be "meter"Ò
*
* The default value is "", meaning the dimensionless unit:
* isDimensionless() will return true, until index is changed.
*/
private String simpleUnitID = "";
/**
* Determine the power of the `SingleUnit`. For example, for "square-meter", the dimensionality will be `2`.
*
* NOTE:
* Default dimensionality is 1.
*/
private int dimensionality = 1;
/**
* SI or binary prefix.
*/
private MeasureUnit.MeasurePrefix unitPrefix = MeasureUnit.MeasurePrefix.ONE;
public SingleUnitImpl copy() {
SingleUnitImpl result = new SingleUnitImpl();
result.index = this.index;
result.dimensionality = this.dimensionality;
result.simpleUnitID = this.simpleUnitID;
result.unitPrefix = this.unitPrefix;
return result;
}
public MeasureUnit build() {
MeasureUnitImpl measureUnit = new MeasureUnitImpl(this);
return measureUnit.build();
}
/**
* Generates a neutral identifier string for a single unit which means we do not include the dimension signal.
*/
public String getNeutralIdentifier() {
StringBuilder result = new StringBuilder();
int absPower = Math.abs(this.getDimensionality());
assert absPower > 0 : "this function does not support the dimensionless single units";
if (absPower == 1) {
// no-op
} else if (absPower == 2) {
result.append("square-");
} else if (absPower == 3) {
result.append("cubic-");
} else if (absPower <= 15) {
result.append("pow");
result.append(absPower);
result.append('-');
} else {
throw new IllegalArgumentException("Unit Identifier Syntax Error");
}
result.append(this.getPrefix().getIdentifier());
result.append(this.getSimpleUnitID());
return result.toString();
}
/**
* Compare this SingleUnitImpl to another SingleUnitImpl for the sake of
* sorting and coalescing.
*
* Sort order of units is specified by UTS #35
* (https://unicode.org/reports/tr35/tr35-info.html#Unit_Identifier_Normalization).
*
* Takes the sign of dimensionality into account, but not the absolute
* value: per-meter is not considered the same as meter, but meter is
* considered the same as square-meter.
*
* The dimensionless unit generally does not get compared, but if it did, it
* would sort before other units by virtue of index being < 0 and
* dimensionality not being negative.
*/
int compareTo(SingleUnitImpl other) {
if (dimensionality < 0 && other.dimensionality > 0) {
// Positive dimensions first
return 1;
}
if (dimensionality > 0 && other.dimensionality < 0) {
return -1;
}
// Sort by official quantity order
int thisCategoryIndex = UnitsData.getCategoryIndexOfSimpleUnit(index);
int otherCategoryIndex = UnitsData.getCategoryIndexOfSimpleUnit(other.index);
if (thisCategoryIndex < otherCategoryIndex) {
return -1;
}
if (thisCategoryIndex > otherCategoryIndex) {
return 1;
}
// If quantity order didn't help, then we go by index.
if (index < other.index) {
return -1;
}
if (index > other.index) {
return 1;
}
// When comparing binary prefixes vs SI prefixes, instead of comparing the actual values, we can
// multiply the binary prefix power by 3 and compare the powers. if they are equal, we can can
// compare the bases.
// NOTE: this methodology will fail if the binary prefix more than or equal 98.
int unitBase = this.unitPrefix.getBase();
int otherUnitBase = other.unitPrefix.getBase();
// Values for comparison purposes only.
int unitPowerComp =
unitBase == 1024 /* Binary Prefix */ ? this.unitPrefix.getPower() * 3
: this.unitPrefix.getPower();
int otherUnitPowerComp =
otherUnitBase == 1024 /* Binary Prefix */ ? other.unitPrefix.getPower() * 3
: other.unitPrefix.getPower();
if (unitPowerComp < otherUnitPowerComp) {
return 1;
}
if (unitPowerComp > otherUnitPowerComp) {
return -1;
}
if (unitBase < otherUnitBase) {
return 1;
}
if (unitBase > otherUnitBase) {
return -1;
}
return 0;
}
/**
* Checks whether this SingleUnitImpl is compatible with another for the purpose of coalescing.
*
* Units with the same base unit and SI or binary prefix should match, except that they must also
* have the same dimensionality sign, such that we don't merge numerator and denominator.
*/
boolean isCompatibleWith(SingleUnitImpl other) {
return (compareTo(other) == 0);
}
public String getSimpleUnitID() {
return simpleUnitID;
}
public void setSimpleUnit(int simpleUnitIndex, String[] simpleUnits) {
this.index = simpleUnitIndex;
this.simpleUnitID = simpleUnits[simpleUnitIndex];
}
public int getDimensionality() {
return dimensionality;
}
public void setDimensionality(int dimensionality) {
this.dimensionality = dimensionality;
}
public MeasureUnit.MeasurePrefix getPrefix() {
return unitPrefix;
}
public void setPrefix(MeasureUnit.MeasurePrefix unitPrefix) {
this.unitPrefix = unitPrefix;
}
// TODO: unused? Delete?
public int getIndex() {
return index;
}
}