// Copyright 2012 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 build
import (
"fmt"
"unicode"
"golang.org/x/text/internal/colltab"
)
const (
defaultSecondary = 0x20
defaultTertiary = 0x2
maxTertiary = 0x1F
)
type rawCE struct {
w []int
ccc uint8
}
func makeRawCE(w []int, ccc uint8) rawCE {
ce := rawCE{w: make([]int, 4), ccc: ccc}
copy(ce.w, w)
return ce
}
// A collation element is represented as an uint32.
// In the typical case, a rune maps to a single collation element. If a rune
// can be the start of a contraction or expands into multiple collation elements,
// then the collation element that is associated with a rune will have a special
// form to represent such m to n mappings. Such special collation elements
// have a value >= 0x80000000.
const (
maxPrimaryBits = 21
maxSecondaryBits = 12
maxTertiaryBits = 8
)
func makeCE(ce rawCE) (uint32, error) {
v, e := colltab.MakeElem(ce.w[0], ce.w[1], ce.w[2], ce.ccc)
return uint32(v), e
}
// For contractions, collation elements are of the form
// 110bbbbb bbbbbbbb iiiiiiii iiiinnnn, where
// - n* is the size of the first node in the contraction trie.
// - i* is the index of the first node in the contraction trie.
// - b* is the offset into the contraction collation element table.
// See contract.go for details on the contraction trie.
const (
contractID = 0xC0000000
maxNBits = 4
maxTrieIndexBits = 12
maxContractOffsetBits = 13
)
func makeContractIndex(h ctHandle, offset int) (uint32, error) {
if h.n >= 1<<maxNBits {
return 0, fmt.Errorf("size of contraction trie node too large: %d >= %d", h.n, 1<<maxNBits)
}
if h.index >= 1<<maxTrieIndexBits {
return 0, fmt.Errorf("size of contraction trie offset too large: %d >= %d", h.index, 1<<maxTrieIndexBits)
}
if offset >= 1<<maxContractOffsetBits {
return 0, fmt.Errorf("contraction offset out of bounds: %x >= %x", offset, 1<<maxContractOffsetBits)
}
ce := uint32(contractID)
ce += uint32(offset << (maxNBits + maxTrieIndexBits))
ce += uint32(h.index << maxNBits)
ce += uint32(h.n)
return ce, nil
}
// For expansions, collation elements are of the form
// 11100000 00000000 bbbbbbbb bbbbbbbb,
// where b* is the index into the expansion sequence table.
const (
expandID = 0xE0000000
maxExpandIndexBits = 16
)
func makeExpandIndex(index int) (uint32, error) {
if index >= 1<<maxExpandIndexBits {
return 0, fmt.Errorf("expansion index out of bounds: %x >= %x", index, 1<<maxExpandIndexBits)
}
return expandID + uint32(index), nil
}
// Each list of collation elements corresponding to an expansion starts with
// a header indicating the length of the sequence.
func makeExpansionHeader(n int) (uint32, error) {
return uint32(n), nil
}
// Some runes can be expanded using NFKD decomposition. Instead of storing the full
// sequence of collation elements, we decompose the rune and lookup the collation
// elements for each rune in the decomposition and modify the tertiary weights.
// The collation element, in this case, is of the form
// 11110000 00000000 wwwwwwww vvvvvvvv, where
// - v* is the replacement tertiary weight for the first rune,
// - w* is the replacement tertiary weight for the second rune,
// Tertiary weights of subsequent runes should be replaced with maxTertiary.
// See https://www.unicode.org/reports/tr10/#Compatibility_Decompositions for more details.
const (
decompID = 0xF0000000
)
func makeDecompose(t1, t2 int) (uint32, error) {
if t1 >= 256 || t1 < 0 {
return 0, fmt.Errorf("first tertiary weight out of bounds: %d >= 256", t1)
}
if t2 >= 256 || t2 < 0 {
return 0, fmt.Errorf("second tertiary weight out of bounds: %d >= 256", t2)
}
return uint32(t2<<8+t1) + decompID, nil
}
const (
// These constants were taken from https://www.unicode.org/versions/Unicode6.0.0/ch12.pdf.
minUnified rune = 0x4E00
maxUnified = 0x9FFF
minCompatibility = 0xF900
maxCompatibility = 0xFAFF
minRare = 0x3400
maxRare = 0x4DBF
)
const (
commonUnifiedOffset = 0x10000
rareUnifiedOffset = 0x20000 // largest rune in common is U+FAFF
otherOffset = 0x50000 // largest rune in rare is U+2FA1D
illegalOffset = otherOffset + int(unicode.MaxRune)
maxPrimary = illegalOffset + 1
)
// implicitPrimary returns the primary weight for the a rune
// for which there is no entry for the rune in the collation table.
// We take a different approach from the one specified in
// https://unicode.org/reports/tr10/#Implicit_Weights,
// but preserve the resulting relative ordering of the runes.
func implicitPrimary(r rune) int {
if unicode.Is(unicode.Ideographic, r) {
if r >= minUnified && r <= maxUnified {
// The most common case for CJK.
return int(r) + commonUnifiedOffset
}
if r >= minCompatibility && r <= maxCompatibility {
// This will typically not hit. The DUCET explicitly specifies mappings
// for all characters that do not decompose.
return int(r) + commonUnifiedOffset
}
return int(r) + rareUnifiedOffset
}
return int(r) + otherOffset
}
// convertLargeWeights converts collation elements with large
// primaries (either double primaries or for illegal runes)
// to our own representation.
// A CJK character C is represented in the DUCET as
// [.FBxx.0020.0002.C][.BBBB.0000.0000.C]
// We will rewrite these characters to a single CE.
// We assume the CJK values start at 0x8000.
// See https://unicode.org/reports/tr10/#Implicit_Weights
func convertLargeWeights(elems []rawCE) (res []rawCE, err error) {
const (
cjkPrimaryStart = 0xFB40
rarePrimaryStart = 0xFB80
otherPrimaryStart = 0xFBC0
illegalPrimary = 0xFFFE
highBitsMask = 0x3F
lowBitsMask = 0x7FFF
lowBitsFlag = 0x8000
shiftBits = 15
)
for i := 0; i < len(elems); i++ {
ce := elems[i].w
p := ce[0]
if p < cjkPrimaryStart {
continue
}
if p > 0xFFFF {
return elems, fmt.Errorf("found primary weight %X; should be <= 0xFFFF", p)
}
if p >= illegalPrimary {
ce[0] = illegalOffset + p - illegalPrimary
} else {
if i+1 >= len(elems) {
return elems, fmt.Errorf("second part of double primary weight missing: %v", elems)
}
if elems[i+1].w[0]&lowBitsFlag == 0 {
return elems, fmt.Errorf("malformed second part of double primary weight: %v", elems)
}
np := ((p & highBitsMask) << shiftBits) + elems[i+1].w[0]&lowBitsMask
switch {
case p < rarePrimaryStart:
np += commonUnifiedOffset
case p < otherPrimaryStart:
np += rareUnifiedOffset
default:
p += otherOffset
}
ce[0] = np
for j := i + 1; j+1 < len(elems); j++ {
elems[j] = elems[j+1]
}
elems = elems[:len(elems)-1]
}
}
return elems, nil
}
// nextWeight computes the first possible collation weights following elems
// for the given level.
func nextWeight(level colltab.Level, elems []rawCE) []rawCE {
if level == colltab.Identity {
next := make([]rawCE, len(elems))
copy(next, elems)
return next
}
next := []rawCE{makeRawCE(elems[0].w, elems[0].ccc)}
next[0].w[level]++
if level < colltab.Secondary {
next[0].w[colltab.Secondary] = defaultSecondary
}
if level < colltab.Tertiary {
next[0].w[colltab.Tertiary] = defaultTertiary
}
// Filter entries that cannot influence ordering.
for _, ce := range elems[1:] {
skip := true
for i := colltab.Primary; i < level; i++ {
skip = skip && ce.w[i] == 0
}
if !skip {
next = append(next, ce)
}
}
return next
}
func nextVal(elems []rawCE, i int, level colltab.Level) (index, value int) {
for ; i < len(elems) && elems[i].w[level] == 0; i++ {
}
if i < len(elems) {
return i, elems[i].w[level]
}
return i, 0
}
// compareWeights returns -1 if a < b, 1 if a > b, or 0 otherwise.
// It also returns the collation level at which the difference is found.
func compareWeights(a, b []rawCE) (result int, level colltab.Level) {
for level := colltab.Primary; level < colltab.Identity; level++ {
var va, vb int
for ia, ib := 0, 0; ia < len(a) || ib < len(b); ia, ib = ia+1, ib+1 {
ia, va = nextVal(a, ia, level)
ib, vb = nextVal(b, ib, level)
if va != vb {
if va < vb {
return -1, level
} else {
return 1, level
}
}
}
}
return 0, colltab.Identity
}
func equalCE(a, b rawCE) bool {
for i := 0; i < 3; i++ {
if b.w[i] != a.w[i] {
return false
}
}
return true
}
func equalCEArrays(a, b []rawCE) bool {
if len(a) != len(b) {
return false
}
for i := range a {
if !equalCE(a[i], b[i]) {
return false
}
}
return true
}
