259 lines
7.3 KiB
Go
259 lines
7.3 KiB
Go
// Copyright 2016 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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//go:generate go run gen.go gen_common.go
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// Package plural provides utilities for handling linguistic plurals in text.
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//
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// The definitions in this package are based on the plural rule handling defined
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// in CLDR. See
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// http://unicode.org/reports/tr35/tr35-numbers.html#Language_Plural_Rules for
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// details.
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package plural
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import (
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"golang.org/x/text/internal/number"
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"golang.org/x/text/language"
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)
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// Rules defines the plural rules for all languages for a certain plural type.
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//
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//
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// This package is UNDER CONSTRUCTION and its API may change.
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type Rules struct {
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rules []pluralCheck
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index []byte
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langToIndex []byte
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inclusionMasks []uint64
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}
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var (
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// Cardinal defines the plural rules for numbers indicating quantities.
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Cardinal *Rules = cardinal
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// Ordinal defines the plural rules for numbers indicating position
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// (first, second, etc.).
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Ordinal *Rules = ordinal
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ordinal = &Rules{
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ordinalRules,
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ordinalIndex,
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ordinalLangToIndex,
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ordinalInclusionMasks[:],
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}
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cardinal = &Rules{
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cardinalRules,
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cardinalIndex,
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cardinalLangToIndex,
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cardinalInclusionMasks[:],
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}
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)
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// getIntApprox converts the digits in slice digits[start:end] to an integer
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// according to the following rules:
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// - Let i be asInt(digits[start:end]), where out-of-range digits are assumed
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// to be zero.
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// - Result n is big if i / 10^nMod > 1.
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// - Otherwise the result is i % 10^nMod.
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//
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// For example, if digits is {1, 2, 3} and start:end is 0:5, then the result
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// for various values of nMod is:
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// - when nMod == 2, n == big
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// - when nMod == 3, n == big
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// - when nMod == 4, n == big
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// - when nMod == 5, n == 12300
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// - when nMod == 6, n == 12300
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// - when nMod == 7, n == 12300
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func getIntApprox(digits []byte, start, end, nMod, big int) (n int) {
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// Leading 0 digits just result in 0.
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p := start
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if p < 0 {
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p = 0
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}
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// Range only over the part for which we have digits.
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mid := end
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if mid >= len(digits) {
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mid = len(digits)
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}
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// Check digits more significant that nMod.
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if q := end - nMod; q > 0 {
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if q > mid {
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q = mid
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}
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for ; p < q; p++ {
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if digits[p] != 0 {
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return big
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}
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}
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}
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for ; p < mid; p++ {
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n = 10*n + int(digits[p])
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}
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// Multiply for trailing zeros.
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for ; p < end; p++ {
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n *= 10
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}
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return n
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}
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// MatchDigits computes the plural form for the given language and the given
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// decimal floating point digits. The digits are stored in big-endian order and
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// are of value byte(0) - byte(9). The floating point position is indicated by
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// exp and the number of visible decimals is scale. All leading and trailing
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// zeros may be omitted from digits.
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//
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// The following table contains examples of possible arguments to represent
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// the given numbers.
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// decimal digits exp scale
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// 123 []byte{1, 2, 3} 3 0
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// 123.4 []byte{1, 2, 3, 4} 3 1
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// 123.40 []byte{1, 2, 3, 4} 3 2
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// 100000 []byte{1} 6 0
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// 100000.00 []byte{1} 6 3
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func (p *Rules) MatchDigits(t language.Tag, digits []byte, exp, scale int) Form {
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index, _ := language.CompactIndex(t)
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// Differentiate up to including mod 1000000 for the integer part.
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n := getIntApprox(digits, 0, exp, 6, 1000000)
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// Differentiate up to including mod 100 for the fractional part.
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f := getIntApprox(digits, exp, exp+scale, 2, 100)
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return matchPlural(p, index, n, f, scale)
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}
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func (p *Rules) matchDisplayDigits(t language.Tag, d *number.Digits) (Form, int) {
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n := getIntApprox(d.Digits, 0, int(d.Exp), 6, 1000000)
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return p.MatchDigits(t, d.Digits, int(d.Exp), d.NumFracDigits()), n
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}
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func validForms(p *Rules, t language.Tag) (forms []Form) {
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index, _ := language.CompactIndex(t)
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offset := p.langToIndex[index]
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rules := p.rules[p.index[offset]:p.index[offset+1]]
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forms = append(forms, Other)
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last := Other
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for _, r := range rules {
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if cat := Form(r.cat & formMask); cat != andNext && last != cat {
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forms = append(forms, cat)
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last = cat
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}
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}
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return forms
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}
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func (p *Rules) matchComponents(t language.Tag, n, f, scale int) Form {
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index, _ := language.CompactIndex(t)
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return matchPlural(p, index, n, f, scale)
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}
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// MatchPlural returns the plural form for the given language and plural
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// operands (as defined in
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// http://unicode.org/reports/tr35/tr35-numbers.html#Language_Plural_Rules):
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// where
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// n absolute value of the source number (integer and decimals)
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// input
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// i integer digits of n.
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// v number of visible fraction digits in n, with trailing zeros.
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// w number of visible fraction digits in n, without trailing zeros.
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// f visible fractional digits in n, with trailing zeros (f = t * 10^(v-w))
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// t visible fractional digits in n, without trailing zeros.
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//
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// If any of the operand values is too large to fit in an int, it is okay to
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// pass the value modulo 10,000,000.
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func (p *Rules) MatchPlural(lang language.Tag, i, v, w, f, t int) Form {
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index, _ := language.CompactIndex(lang)
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return matchPlural(p, index, i, f, v)
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}
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func matchPlural(p *Rules, index int, n, f, v int) Form {
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nMask := p.inclusionMasks[n%maxMod]
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// Compute the fMask inline in the rules below, as it is relatively rare.
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// fMask := p.inclusionMasks[f%maxMod]
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vMask := p.inclusionMasks[v%maxMod]
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// Do the matching
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offset := p.langToIndex[index]
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rules := p.rules[p.index[offset]:p.index[offset+1]]
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for i := 0; i < len(rules); i++ {
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rule := rules[i]
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setBit := uint64(1 << rule.setID)
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var skip bool
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switch op := opID(rule.cat >> opShift); op {
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case opI: // i = x
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skip = n >= numN || nMask&setBit == 0
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case opI | opNotEqual: // i != x
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skip = n < numN && nMask&setBit != 0
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case opI | opMod: // i % m = x
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skip = nMask&setBit == 0
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case opI | opMod | opNotEqual: // i % m != x
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skip = nMask&setBit != 0
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case opN: // n = x
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skip = f != 0 || n >= numN || nMask&setBit == 0
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case opN | opNotEqual: // n != x
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skip = f == 0 && n < numN && nMask&setBit != 0
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case opN | opMod: // n % m = x
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skip = f != 0 || nMask&setBit == 0
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case opN | opMod | opNotEqual: // n % m != x
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skip = f == 0 && nMask&setBit != 0
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case opF: // f = x
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skip = f >= numN || p.inclusionMasks[f%maxMod]&setBit == 0
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case opF | opNotEqual: // f != x
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skip = f < numN && p.inclusionMasks[f%maxMod]&setBit != 0
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case opF | opMod: // f % m = x
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skip = p.inclusionMasks[f%maxMod]&setBit == 0
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case opF | opMod | opNotEqual: // f % m != x
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skip = p.inclusionMasks[f%maxMod]&setBit != 0
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case opV: // v = x
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skip = v < numN && vMask&setBit == 0
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case opV | opNotEqual: // v != x
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skip = v < numN && vMask&setBit != 0
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case opW: // w == 0
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skip = f != 0
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case opW | opNotEqual: // w != 0
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skip = f == 0
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// Hard-wired rules that cannot be handled by our algorithm.
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case opBretonM:
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skip = f != 0 || n == 0 || n%1000000 != 0
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case opAzerbaijan00s:
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// 100,200,300,400,500,600,700,800,900
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skip = n == 0 || n >= 1000 || n%100 != 0
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case opItalian800:
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skip = (f != 0 || n >= numN || nMask&setBit == 0) && n != 800
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}
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if skip {
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// advance over AND entries.
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for ; i < len(rules) && rules[i].cat&formMask == andNext; i++ {
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}
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continue
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}
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// return if we have a final entry.
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if cat := rule.cat & formMask; cat != andNext {
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return Form(cat)
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}
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}
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return Other
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}
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