Switch to using the dep tool and update all the dependencies

vendor/golang.org/x/text/internal/colltab/numeric.go

@@ -0,0 +1,236 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package colltab
+
+import (
+	"unicode"
+	"unicode/utf8"
+)
+
+// NewNumericWeighter wraps w to replace individual digits to sort based on their
+// numeric value.
+//
+// Weighter w must have a free primary weight after the primary weight for 9.
+// If this is not the case, numeric value will sort at the same primary level
+// as the first primary sorting after 9.
+func NewNumericWeighter(w Weighter) Weighter {
+	getElem := func(s string) Elem {
+		elems, _ := w.AppendNextString(nil, s)
+		return elems[0]
+	}
+	nine := getElem("9")
+
+	// Numbers should order before zero, but the DUCET has no room for this.
+	// TODO: move before zero once we use fractional collation elements.
+	ns, _ := MakeElem(nine.Primary()+1, nine.Secondary(), int(nine.Tertiary()), 0)
+
+	return &numericWeighter{
+		Weighter: w,
+
+		// We assume that w sorts digits of different kinds in order of numeric
+		// value and that the tertiary weight order is preserved.
+		//
+		// TODO: evaluate whether it is worth basing the ranges on the Elem
+		// encoding itself once the move to fractional weights is complete.
+		zero:          getElem("0"),
+		zeroSpecialLo: getElem("０"), // U+FF10 FULLWIDTH DIGIT ZERO
+		zeroSpecialHi: getElem("₀"), // U+2080 SUBSCRIPT ZERO
+		nine:          nine,
+		nineSpecialHi: getElem("₉"), // U+2089 SUBSCRIPT NINE
+		numberStart:   ns,
+	}
+}
+
+// A numericWeighter translates a stream of digits into a stream of weights
+// representing the numeric value.
+type numericWeighter struct {
+	Weighter
+
+	// The Elems below all demarcate boundaries of specific ranges. With the
+	// current element encoding digits are in two ranges: normal (default
+	// tertiary value) and special. For most languages, digits have collation
+	// elements in the normal range.
+	//
+	// Note: the range tests are very specific for the element encoding used by
+	// this implementation. The tests in collate_test.go are designed to fail
+	// if this code is not updated when an encoding has changed.
+
+	zero          Elem // normal digit zero
+	zeroSpecialLo Elem // special digit zero, low tertiary value
+	zeroSpecialHi Elem // special digit zero, high tertiary value
+	nine          Elem // normal digit nine
+	nineSpecialHi Elem // special digit nine
+	numberStart   Elem
+}
+
+// AppendNext calls the namesake of the underlying weigher, but replaces single
+// digits with weights representing their value.
+func (nw *numericWeighter) AppendNext(buf []Elem, s []byte) (ce []Elem, n int) {
+	ce, n = nw.Weighter.AppendNext(buf, s)
+	nc := numberConverter{
+		elems: buf,
+		w:     nw,
+		b:     s,
+	}
+	isZero, ok := nc.checkNextDigit(ce)
+	if !ok {
+		return ce, n
+	}
+	// ce might have been grown already, so take it instead of buf.
+	nc.init(ce, len(buf), isZero)
+	for n < len(s) {
+		ce, sz := nw.Weighter.AppendNext(nc.elems, s[n:])
+		nc.b = s
+		n += sz
+		if !nc.update(ce) {
+			break
+		}
+	}
+	return nc.result(), n
+}
+
+// AppendNextString calls the namesake of the underlying weigher, but replaces
+// single digits with weights representing their value.
+func (nw *numericWeighter) AppendNextString(buf []Elem, s string) (ce []Elem, n int) {
+	ce, n = nw.Weighter.AppendNextString(buf, s)
+	nc := numberConverter{
+		elems: buf,
+		w:     nw,
+		s:     s,
+	}
+	isZero, ok := nc.checkNextDigit(ce)
+	if !ok {
+		return ce, n
+	}
+	nc.init(ce, len(buf), isZero)
+	for n < len(s) {
+		ce, sz := nw.Weighter.AppendNextString(nc.elems, s[n:])
+		nc.s = s
+		n += sz
+		if !nc.update(ce) {
+			break
+		}
+	}
+	return nc.result(), n
+}
+
+type numberConverter struct {
+	w *numericWeighter
+
+	elems    []Elem
+	nDigits  int
+	lenIndex int
+
+	s string // set if the input was of type string
+	b []byte // set if the input was of type []byte
+}
+
+// init completes initialization of a numberConverter and prepares it for adding
+// more digits. elems is assumed to have a digit starting at oldLen.
+func (nc *numberConverter) init(elems []Elem, oldLen int, isZero bool) {
+	// Insert a marker indicating the start of a number and and a placeholder
+	// for the number of digits.
+	if isZero {
+		elems = append(elems[:oldLen], nc.w.numberStart, 0)
+	} else {
+		elems = append(elems, 0, 0)
+		copy(elems[oldLen+2:], elems[oldLen:])
+		elems[oldLen] = nc.w.numberStart
+		elems[oldLen+1] = 0
+
+		nc.nDigits = 1
+	}
+	nc.elems = elems
+	nc.lenIndex = oldLen + 1
+}
+
+// checkNextDigit reports whether bufNew adds a single digit relative to the old
+// buffer. If it does, it also reports whether this digit is zero.
+func (nc *numberConverter) checkNextDigit(bufNew []Elem) (isZero, ok bool) {
+	if len(nc.elems) >= len(bufNew) {
+		return false, false
+	}
+	e := bufNew[len(nc.elems)]
+	if e < nc.w.zeroSpecialLo || nc.w.nine < e {
+		// Not a number.
+		return false, false
+	}
+	if e < nc.w.zero {
+		if e > nc.w.nineSpecialHi {
+			// Not a number.
+			return false, false
+		}
+		if !nc.isDigit() {
+			return false, false
+		}
+		isZero = e <= nc.w.zeroSpecialHi
+	} else {
+		// This is the common case if we encounter a digit.
+		isZero = e == nc.w.zero
+	}
+	// Test the remaining added collation elements have a zero primary value.
+	if n := len(bufNew) - len(nc.elems); n > 1 {
+		for i := len(nc.elems) + 1; i < len(bufNew); i++ {
+			if bufNew[i].Primary() != 0 {
+				return false, false
+			}
+		}
+		// In some rare cases, collation elements will encode runes in
+		// unicode.No as a digit. For example Ethiopic digits (U+1369 - U+1371)
+		// are not in Nd. Also some digits that clearly belong in unicode.No,
+		// like U+0C78 TELUGU FRACTION DIGIT ZERO FOR ODD POWERS OF FOUR, have
+		// collation elements indistinguishable from normal digits.
+		// Unfortunately, this means we need to make this check for nearly all
+		// non-Latin digits.
+		//
+		// TODO: check the performance impact and find something better if it is
+		// an issue.
+		if !nc.isDigit() {
+			return false, false
+		}
+	}
+	return isZero, true
+}
+
+func (nc *numberConverter) isDigit() bool {
+	if nc.b != nil {
+		r, _ := utf8.DecodeRune(nc.b)
+		return unicode.In(r, unicode.Nd)
+	}
+	r, _ := utf8.DecodeRuneInString(nc.s)
+	return unicode.In(r, unicode.Nd)
+}
+
+// We currently support a maximum of about 2M digits (the number of primary
+// values). Such numbers will compare correctly against small numbers, but their
+// comparison against other large numbers is undefined.
+//
+// TODO: define a proper fallback, such as comparing large numbers textually or
+// actually allowing numbers of unlimited length.
+//
+// TODO: cap this to a lower number (like 100) and maybe allow a larger number
+// in an option?
+const maxDigits = 1<<maxPrimaryBits - 1
+
+func (nc *numberConverter) update(elems []Elem) bool {
+	isZero, ok := nc.checkNextDigit(elems)
+	if nc.nDigits == 0 && isZero {
+		return true
+	}
+	nc.elems = elems
+	if !ok {
+		return false
+	}
+	nc.nDigits++
+	return nc.nDigits < maxDigits
+}
+
+// result fills in the length element for the digit sequence and returns the
+// completed collation elements.
+func (nc *numberConverter) result() []Elem {
+	e, _ := MakeElem(nc.nDigits, defaultSecondary, defaultTertiary, 0)
+	nc.elems[nc.lenIndex] = e
+	return nc.elems
+}