--- /dev/null
+// 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"
+ "io"
+ "reflect"
+ "sort"
+ "strings"
+
+ "golang.org/x/text/internal/colltab"
+)
+
+// This file contains code for detecting contractions and generating
+// the necessary tables.
+// Any Unicode Collation Algorithm (UCA) table entry that has more than
+// one rune one the left-hand side is called a contraction.
+// See http://www.unicode.org/reports/tr10/#Contractions for more details.
+//
+// We define the following terms:
+// initial: a rune that appears as the first rune in a contraction.
+// suffix: a sequence of runes succeeding the initial rune
+// in a given contraction.
+// non-initial: a rune that appears in a suffix.
+//
+// A rune may be both a initial and a non-initial and may be so in
+// many contractions. An initial may typically also appear by itself.
+// In case of ambiguities, the UCA requires we match the longest
+// contraction.
+//
+// Many contraction rules share the same set of possible suffixes.
+// We store sets of suffixes in a trie that associates an index with
+// each suffix in the set. This index can be used to look up a
+// collation element associated with the (starter rune, suffix) pair.
+//
+// The trie is defined on a UTF-8 byte sequence.
+// The overall trie is represented as an array of ctEntries. Each node of the trie
+// is represented as a subsequence of ctEntries, where each entry corresponds to
+// a possible match of a next character in the search string. An entry
+// also includes the length and offset to the next sequence of entries
+// to check in case of a match.
+
+const (
+ final = 0
+ noIndex = 0xFF
+)
+
+// ctEntry associates to a matching byte an offset and/or next sequence of
+// bytes to check. A ctEntry c is called final if a match means that the
+// longest suffix has been found. An entry c is final if c.N == 0.
+// A single final entry can match a range of characters to an offset.
+// A non-final entry always matches a single byte. Note that a non-final
+// entry might still resemble a completed suffix.
+// Examples:
+// The suffix strings "ab" and "ac" can be represented as:
+// []ctEntry{
+// {'a', 1, 1, noIndex}, // 'a' by itself does not match, so i is 0xFF.
+// {'b', 'c', 0, 1}, // "ab" -> 1, "ac" -> 2
+// }
+//
+// The suffix strings "ab", "abc", "abd", and "abcd" can be represented as:
+// []ctEntry{
+// {'a', 1, 1, noIndex}, // 'a' must be followed by 'b'.
+// {'b', 1, 2, 1}, // "ab" -> 1, may be followed by 'c' or 'd'.
+// {'d', 'd', final, 3}, // "abd" -> 3
+// {'c', 4, 1, 2}, // "abc" -> 2, may be followed by 'd'.
+// {'d', 'd', final, 4}, // "abcd" -> 4
+// }
+// See genStateTests in contract_test.go for more examples.
+type ctEntry struct {
+ L uint8 // non-final: byte value to match; final: lowest match in range.
+ H uint8 // non-final: relative index to next block; final: highest match in range.
+ N uint8 // non-final: length of next block; final: final
+ I uint8 // result offset. Will be noIndex if more bytes are needed to complete.
+}
+
+// contractTrieSet holds a set of contraction tries. The tries are stored
+// consecutively in the entry field.
+type contractTrieSet []struct{ l, h, n, i uint8 }
+
+// ctHandle is used to identify a trie in the trie set, consisting in an offset
+// in the array and the size of the first node.
+type ctHandle struct {
+ index, n int
+}
+
+// appendTrie adds a new trie for the given suffixes to the trie set and returns
+// a handle to it. The handle will be invalid on error.
+func appendTrie(ct *colltab.ContractTrieSet, suffixes []string) (ctHandle, error) {
+ es := make([]stridx, len(suffixes))
+ for i, s := range suffixes {
+ es[i].str = s
+ }
+ sort.Sort(offsetSort(es))
+ for i := range es {
+ es[i].index = i + 1
+ }
+ sort.Sort(genidxSort(es))
+ i := len(*ct)
+ n, err := genStates(ct, es)
+ if err != nil {
+ *ct = (*ct)[:i]
+ return ctHandle{}, err
+ }
+ return ctHandle{i, n}, nil
+}
+
+// genStates generates ctEntries for a given suffix set and returns
+// the number of entries for the first node.
+func genStates(ct *colltab.ContractTrieSet, sis []stridx) (int, error) {
+ if len(sis) == 0 {
+ return 0, fmt.Errorf("genStates: list of suffices must be non-empty")
+ }
+ start := len(*ct)
+ // create entries for differing first bytes.
+ for _, si := range sis {
+ s := si.str
+ if len(s) == 0 {
+ continue
+ }
+ added := false
+ c := s[0]
+ if len(s) > 1 {
+ for j := len(*ct) - 1; j >= start; j-- {
+ if (*ct)[j].L == c {
+ added = true
+ break
+ }
+ }
+ if !added {
+ *ct = append(*ct, ctEntry{L: c, I: noIndex})
+ }
+ } else {
+ for j := len(*ct) - 1; j >= start; j-- {
+ // Update the offset for longer suffixes with the same byte.
+ if (*ct)[j].L == c {
+ (*ct)[j].I = uint8(si.index)
+ added = true
+ }
+ // Extend range of final ctEntry, if possible.
+ if (*ct)[j].H+1 == c {
+ (*ct)[j].H = c
+ added = true
+ }
+ }
+ if !added {
+ *ct = append(*ct, ctEntry{L: c, H: c, N: final, I: uint8(si.index)})
+ }
+ }
+ }
+ n := len(*ct) - start
+ // Append nodes for the remainder of the suffixes for each ctEntry.
+ sp := 0
+ for i, end := start, len(*ct); i < end; i++ {
+ fe := (*ct)[i]
+ if fe.H == 0 { // uninitialized non-final
+ ln := len(*ct) - start - n
+ if ln > 0xFF {
+ return 0, fmt.Errorf("genStates: relative block offset too large: %d > 255", ln)
+ }
+ fe.H = uint8(ln)
+ // Find first non-final strings with same byte as current entry.
+ for ; sis[sp].str[0] != fe.L; sp++ {
+ }
+ se := sp + 1
+ for ; se < len(sis) && len(sis[se].str) > 1 && sis[se].str[0] == fe.L; se++ {
+ }
+ sl := sis[sp:se]
+ sp = se
+ for i, si := range sl {
+ sl[i].str = si.str[1:]
+ }
+ nn, err := genStates(ct, sl)
+ if err != nil {
+ return 0, err
+ }
+ fe.N = uint8(nn)
+ (*ct)[i] = fe
+ }
+ }
+ sort.Sort(entrySort((*ct)[start : start+n]))
+ return n, nil
+}
+
+// There may be both a final and non-final entry for a byte if the byte
+// is implied in a range of matches in the final entry.
+// We need to ensure that the non-final entry comes first in that case.
+type entrySort colltab.ContractTrieSet
+
+func (fe entrySort) Len() int { return len(fe) }
+func (fe entrySort) Swap(i, j int) { fe[i], fe[j] = fe[j], fe[i] }
+func (fe entrySort) Less(i, j int) bool {
+ return fe[i].L > fe[j].L
+}
+
+// stridx is used for sorting suffixes and their associated offsets.
+type stridx struct {
+ str string
+ index int
+}
+
+// For computing the offsets, we first sort by size, and then by string.
+// This ensures that strings that only differ in the last byte by 1
+// are sorted consecutively in increasing order such that they can
+// be packed as a range in a final ctEntry.
+type offsetSort []stridx
+
+func (si offsetSort) Len() int { return len(si) }
+func (si offsetSort) Swap(i, j int) { si[i], si[j] = si[j], si[i] }
+func (si offsetSort) Less(i, j int) bool {
+ if len(si[i].str) != len(si[j].str) {
+ return len(si[i].str) > len(si[j].str)
+ }
+ return si[i].str < si[j].str
+}
+
+// For indexing, we want to ensure that strings are sorted in string order, where
+// for strings with the same prefix, we put longer strings before shorter ones.
+type genidxSort []stridx
+
+func (si genidxSort) Len() int { return len(si) }
+func (si genidxSort) Swap(i, j int) { si[i], si[j] = si[j], si[i] }
+func (si genidxSort) Less(i, j int) bool {
+ if strings.HasPrefix(si[j].str, si[i].str) {
+ return false
+ }
+ if strings.HasPrefix(si[i].str, si[j].str) {
+ return true
+ }
+ return si[i].str < si[j].str
+}
+
+// lookup matches the longest suffix in str and returns the associated offset
+// and the number of bytes consumed.
+func lookup(ct *colltab.ContractTrieSet, h ctHandle, str []byte) (index, ns int) {
+ states := (*ct)[h.index:]
+ p := 0
+ n := h.n
+ for i := 0; i < n && p < len(str); {
+ e := states[i]
+ c := str[p]
+ if c >= e.L {
+ if e.L == c {
+ p++
+ if e.I != noIndex {
+ index, ns = int(e.I), p
+ }
+ if e.N != final {
+ // set to new state
+ i, states, n = 0, states[int(e.H)+n:], int(e.N)
+ } else {
+ return
+ }
+ continue
+ } else if e.N == final && c <= e.H {
+ p++
+ return int(c-e.L) + int(e.I), p
+ }
+ }
+ i++
+ }
+ return
+}
+
+// print writes the contractTrieSet t as compilable Go code to w. It returns
+// the total number of bytes written and the size of the resulting data structure in bytes.
+func print(t *colltab.ContractTrieSet, w io.Writer, name string) (n, size int, err error) {
+ update3 := func(nn, sz int, e error) {
+ n += nn
+ if err == nil {
+ err = e
+ }
+ size += sz
+ }
+ update2 := func(nn int, e error) { update3(nn, 0, e) }
+
+ update3(printArray(*t, w, name))
+ update2(fmt.Fprintf(w, "var %sContractTrieSet = ", name))
+ update3(printStruct(*t, w, name))
+ update2(fmt.Fprintln(w))
+ return
+}
+
+func printArray(ct colltab.ContractTrieSet, w io.Writer, name string) (n, size int, err error) {
+ p := func(f string, a ...interface{}) {
+ nn, e := fmt.Fprintf(w, f, a...)
+ n += nn
+ if err == nil {
+ err = e
+ }
+ }
+ size = len(ct) * 4
+ p("// %sCTEntries: %d entries, %d bytes\n", name, len(ct), size)
+ p("var %sCTEntries = [%d]struct{L,H,N,I uint8}{\n", name, len(ct))
+ for _, fe := range ct {
+ p("\t{0x%X, 0x%X, %d, %d},\n", fe.L, fe.H, fe.N, fe.I)
+ }
+ p("}\n")
+ return
+}
+
+func printStruct(ct colltab.ContractTrieSet, w io.Writer, name string) (n, size int, err error) {
+ n, err = fmt.Fprintf(w, "colltab.ContractTrieSet( %sCTEntries[:] )", name)
+ size = int(reflect.TypeOf(ct).Size())
+ return
+}
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