forked from golang/hotime
486 lines
12 KiB
Go
486 lines
12 KiB
Go
// Copyright 2015 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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package number
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import (
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"errors"
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"unicode/utf8"
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)
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// This file contains a parser for the CLDR number patterns as described in
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// https://unicode.org/reports/tr35/tr35-numbers.html#Number_Format_Patterns.
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//
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// The following BNF is derived from this standard.
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//
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// pattern := subpattern (';' subpattern)?
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// subpattern := affix? number exponent? affix?
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// number := decimal | sigDigits
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// decimal := '#'* '0'* ('.' fraction)? | '#' | '0'
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// fraction := '0'* '#'*
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// sigDigits := '#'* '@' '@'* '#'*
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// exponent := 'E' '+'? '0'* '0'
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// padSpec := '*' \L
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//
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// Notes:
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// - An affix pattern may contain any runes, but runes with special meaning
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// should be escaped.
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// - Sequences of digits, '#', and '@' in decimal and sigDigits may have
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// interstitial commas.
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// TODO: replace special characters in affixes (-, +, ¤) with control codes.
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// Pattern holds information for formatting numbers. It is designed to hold
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// information from CLDR number patterns.
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//
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// This pattern is precompiled for all patterns for all languages. Even though
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// the number of patterns is not very large, we want to keep this small.
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//
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// This type is only intended for internal use.
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type Pattern struct {
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RoundingContext
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Affix string // includes prefix and suffix. First byte is prefix length.
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Offset uint16 // Offset into Affix for prefix and suffix
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NegOffset uint16 // Offset into Affix for negative prefix and suffix or 0.
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PadRune rune
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FormatWidth uint16
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GroupingSize [2]uint8
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Flags PatternFlag
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}
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// A RoundingContext indicates how a number should be converted to digits.
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// It contains all information needed to determine the "visible digits" as
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// required by the pluralization rules.
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type RoundingContext struct {
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// TODO: unify these two fields so that there is a more unambiguous meaning
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// of how precision is handled.
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MaxSignificantDigits int16 // -1 is unlimited
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MaxFractionDigits int16 // -1 is unlimited
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Increment uint32
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IncrementScale uint8 // May differ from printed scale.
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Mode RoundingMode
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DigitShift uint8 // Number of decimals to shift. Used for % and ‰.
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// Number of digits.
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MinIntegerDigits uint8
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MaxIntegerDigits uint8
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MinFractionDigits uint8
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MinSignificantDigits uint8
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MinExponentDigits uint8
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}
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// RoundSignificantDigits returns the number of significant digits an
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// implementation of Convert may round to or n < 0 if there is no maximum or
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// a maximum is not recommended.
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func (r *RoundingContext) RoundSignificantDigits() (n int) {
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if r.MaxFractionDigits == 0 && r.MaxSignificantDigits > 0 {
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return int(r.MaxSignificantDigits)
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} else if r.isScientific() && r.MaxIntegerDigits == 1 {
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if r.MaxSignificantDigits == 0 ||
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int(r.MaxFractionDigits+1) == int(r.MaxSignificantDigits) {
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// Note: don't add DigitShift: it is only used for decimals.
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return int(r.MaxFractionDigits) + 1
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}
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}
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return -1
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}
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// RoundFractionDigits returns the number of fraction digits an implementation
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// of Convert may round to or n < 0 if there is no maximum or a maximum is not
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// recommended.
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func (r *RoundingContext) RoundFractionDigits() (n int) {
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if r.MinExponentDigits == 0 &&
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r.MaxSignificantDigits == 0 &&
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r.MaxFractionDigits >= 0 {
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return int(r.MaxFractionDigits) + int(r.DigitShift)
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}
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return -1
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}
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// SetScale fixes the RoundingContext to a fixed number of fraction digits.
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func (r *RoundingContext) SetScale(scale int) {
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r.MinFractionDigits = uint8(scale)
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r.MaxFractionDigits = int16(scale)
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}
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func (r *RoundingContext) SetPrecision(prec int) {
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r.MaxSignificantDigits = int16(prec)
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}
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func (r *RoundingContext) isScientific() bool {
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return r.MinExponentDigits > 0
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}
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func (f *Pattern) needsSep(pos int) bool {
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p := pos - 1
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size := int(f.GroupingSize[0])
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if size == 0 || p == 0 {
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return false
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}
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if p == size {
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return true
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}
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if p -= size; p < 0 {
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return false
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}
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// TODO: make second groupingsize the same as first if 0 so that we can
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// avoid this check.
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if x := int(f.GroupingSize[1]); x != 0 {
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size = x
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}
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return p%size == 0
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}
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// A PatternFlag is a bit mask for the flag field of a Pattern.
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type PatternFlag uint8
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const (
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AlwaysSign PatternFlag = 1 << iota
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ElideSign // Use space instead of plus sign. AlwaysSign must be true.
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AlwaysExpSign
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AlwaysDecimalSeparator
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ParenthesisForNegative // Common pattern. Saves space.
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PadAfterNumber
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PadAfterAffix
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PadBeforePrefix = 0 // Default
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PadAfterPrefix = PadAfterAffix
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PadBeforeSuffix = PadAfterNumber
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PadAfterSuffix = PadAfterNumber | PadAfterAffix
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PadMask = PadAfterNumber | PadAfterAffix
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)
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type parser struct {
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*Pattern
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leadingSharps int
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pos int
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err error
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doNotTerminate bool
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groupingCount uint
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hasGroup bool
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buf []byte
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}
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func (p *parser) setError(err error) {
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if p.err == nil {
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p.err = err
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}
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}
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func (p *parser) updateGrouping() {
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if p.hasGroup &&
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0 < p.groupingCount && p.groupingCount < 255 {
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p.GroupingSize[1] = p.GroupingSize[0]
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p.GroupingSize[0] = uint8(p.groupingCount)
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}
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p.groupingCount = 0
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p.hasGroup = true
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}
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var (
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// TODO: more sensible and localizeable error messages.
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errMultiplePadSpecifiers = errors.New("format: pattern has multiple pad specifiers")
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errInvalidPadSpecifier = errors.New("format: invalid pad specifier")
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errInvalidQuote = errors.New("format: invalid quote")
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errAffixTooLarge = errors.New("format: prefix or suffix exceeds maximum UTF-8 length of 256 bytes")
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errDuplicatePercentSign = errors.New("format: duplicate percent sign")
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errDuplicatePermilleSign = errors.New("format: duplicate permille sign")
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errUnexpectedEnd = errors.New("format: unexpected end of pattern")
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)
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// ParsePattern extracts formatting information from a CLDR number pattern.
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//
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// See https://unicode.org/reports/tr35/tr35-numbers.html#Number_Format_Patterns.
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func ParsePattern(s string) (f *Pattern, err error) {
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p := parser{Pattern: &Pattern{}}
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s = p.parseSubPattern(s)
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if s != "" {
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// Parse negative sub pattern.
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if s[0] != ';' {
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p.setError(errors.New("format: error parsing first sub pattern"))
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return nil, p.err
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}
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neg := parser{Pattern: &Pattern{}} // just for extracting the affixes.
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s = neg.parseSubPattern(s[len(";"):])
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p.NegOffset = uint16(len(p.buf))
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p.buf = append(p.buf, neg.buf...)
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}
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if s != "" {
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p.setError(errors.New("format: spurious characters at end of pattern"))
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}
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if p.err != nil {
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return nil, p.err
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}
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if affix := string(p.buf); affix == "\x00\x00" || affix == "\x00\x00\x00\x00" {
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// No prefix or suffixes.
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p.NegOffset = 0
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} else {
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p.Affix = affix
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}
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if p.Increment == 0 {
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p.IncrementScale = 0
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}
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return p.Pattern, nil
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}
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func (p *parser) parseSubPattern(s string) string {
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s = p.parsePad(s, PadBeforePrefix)
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s = p.parseAffix(s)
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s = p.parsePad(s, PadAfterPrefix)
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s = p.parse(p.number, s)
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p.updateGrouping()
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s = p.parsePad(s, PadBeforeSuffix)
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s = p.parseAffix(s)
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s = p.parsePad(s, PadAfterSuffix)
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return s
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}
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func (p *parser) parsePad(s string, f PatternFlag) (tail string) {
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if len(s) >= 2 && s[0] == '*' {
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r, sz := utf8.DecodeRuneInString(s[1:])
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if p.PadRune != 0 {
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p.err = errMultiplePadSpecifiers
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} else {
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p.Flags |= f
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p.PadRune = r
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}
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return s[1+sz:]
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}
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return s
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}
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func (p *parser) parseAffix(s string) string {
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x := len(p.buf)
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p.buf = append(p.buf, 0) // placeholder for affix length
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s = p.parse(p.affix, s)
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n := len(p.buf) - x - 1
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if n > 0xFF {
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p.setError(errAffixTooLarge)
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}
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p.buf[x] = uint8(n)
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return s
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}
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// state implements a state transition. It returns the new state. A state
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// function may set an error on the parser or may simply return on an incorrect
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// token and let the next phase fail.
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type state func(r rune) state
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// parse repeatedly applies a state function on the given string until a
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// termination condition is reached.
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func (p *parser) parse(fn state, s string) (tail string) {
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for i, r := range s {
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p.doNotTerminate = false
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if fn = fn(r); fn == nil || p.err != nil {
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return s[i:]
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}
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p.FormatWidth++
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}
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if p.doNotTerminate {
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p.setError(errUnexpectedEnd)
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}
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return ""
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}
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func (p *parser) affix(r rune) state {
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switch r {
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case '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
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'#', '@', '.', '*', ',', ';':
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return nil
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case '\'':
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p.FormatWidth--
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return p.escapeFirst
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case '%':
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if p.DigitShift != 0 {
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p.setError(errDuplicatePercentSign)
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}
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p.DigitShift = 2
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case '\u2030': // ‰ Per mille
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if p.DigitShift != 0 {
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p.setError(errDuplicatePermilleSign)
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}
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p.DigitShift = 3
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// TODO: handle currency somehow: ¤, ¤¤, ¤¤¤, ¤¤¤¤
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}
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p.buf = append(p.buf, string(r)...)
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return p.affix
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}
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func (p *parser) escapeFirst(r rune) state {
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switch r {
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case '\'':
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p.buf = append(p.buf, "\\'"...)
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return p.affix
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default:
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p.buf = append(p.buf, '\'')
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p.buf = append(p.buf, string(r)...)
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}
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return p.escape
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}
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func (p *parser) escape(r rune) state {
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switch r {
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case '\'':
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p.FormatWidth--
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p.buf = append(p.buf, '\'')
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return p.affix
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default:
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p.buf = append(p.buf, string(r)...)
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}
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return p.escape
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}
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// number parses a number. The BNF says the integer part should always have
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// a '0', but that does not appear to be the case according to the rest of the
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// documentation. We will allow having only '#' numbers.
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func (p *parser) number(r rune) state {
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switch r {
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case '#':
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p.groupingCount++
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p.leadingSharps++
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case '@':
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p.groupingCount++
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p.leadingSharps = 0
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p.MaxFractionDigits = -1
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return p.sigDigits(r)
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case ',':
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if p.leadingSharps == 0 { // no leading commas
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return nil
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}
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p.updateGrouping()
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case 'E':
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p.MaxIntegerDigits = uint8(p.leadingSharps)
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return p.exponent
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case '.': // allow ".##" etc.
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p.updateGrouping()
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return p.fraction
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case '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
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return p.integer(r)
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default:
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return nil
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}
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return p.number
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}
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func (p *parser) integer(r rune) state {
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if !('0' <= r && r <= '9') {
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var next state
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switch r {
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case 'E':
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if p.leadingSharps > 0 {
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p.MaxIntegerDigits = uint8(p.leadingSharps) + p.MinIntegerDigits
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}
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next = p.exponent
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case '.':
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next = p.fraction
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case ',':
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next = p.integer
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}
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p.updateGrouping()
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return next
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}
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p.Increment = p.Increment*10 + uint32(r-'0')
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p.groupingCount++
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p.MinIntegerDigits++
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return p.integer
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}
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func (p *parser) sigDigits(r rune) state {
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switch r {
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case '@':
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p.groupingCount++
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p.MaxSignificantDigits++
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p.MinSignificantDigits++
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case '#':
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return p.sigDigitsFinal(r)
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case 'E':
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p.updateGrouping()
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return p.normalizeSigDigitsWithExponent()
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default:
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p.updateGrouping()
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return nil
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}
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return p.sigDigits
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}
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func (p *parser) sigDigitsFinal(r rune) state {
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switch r {
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case '#':
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p.groupingCount++
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p.MaxSignificantDigits++
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case 'E':
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p.updateGrouping()
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return p.normalizeSigDigitsWithExponent()
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default:
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p.updateGrouping()
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return nil
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}
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return p.sigDigitsFinal
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}
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func (p *parser) normalizeSigDigitsWithExponent() state {
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p.MinIntegerDigits, p.MaxIntegerDigits = 1, 1
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p.MinFractionDigits = p.MinSignificantDigits - 1
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p.MaxFractionDigits = p.MaxSignificantDigits - 1
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p.MinSignificantDigits, p.MaxSignificantDigits = 0, 0
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return p.exponent
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}
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func (p *parser) fraction(r rune) state {
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switch r {
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case '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
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p.Increment = p.Increment*10 + uint32(r-'0')
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p.IncrementScale++
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p.MinFractionDigits++
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p.MaxFractionDigits++
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case '#':
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p.MaxFractionDigits++
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case 'E':
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if p.leadingSharps > 0 {
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p.MaxIntegerDigits = uint8(p.leadingSharps) + p.MinIntegerDigits
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}
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return p.exponent
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default:
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return nil
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}
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return p.fraction
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}
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func (p *parser) exponent(r rune) state {
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switch r {
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case '+':
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// Set mode and check it wasn't already set.
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if p.Flags&AlwaysExpSign != 0 || p.MinExponentDigits > 0 {
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break
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}
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p.Flags |= AlwaysExpSign
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p.doNotTerminate = true
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return p.exponent
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case '0':
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p.MinExponentDigits++
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return p.exponent
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}
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// termination condition
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if p.MinExponentDigits == 0 {
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p.setError(errors.New("format: need at least one digit"))
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}
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return nil
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}
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