--- /dev/null
+// Copyright 2015 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 search
+
+import (
+ "golang.org/x/text/internal/colltab"
+)
+
+// TODO: handle variable primary weights?
+
+func (p *Pattern) deleteEmptyElements() {
+ k := 0
+ for _, e := range p.ce {
+ if !isIgnorable(p.m, e) {
+ p.ce[k] = e
+ k++
+ }
+ }
+ p.ce = p.ce[:k]
+}
+
+func isIgnorable(m *Matcher, e colltab.Elem) bool {
+ if e.Primary() > 0 {
+ return false
+ }
+ if e.Secondary() > 0 {
+ if !m.ignoreDiacritics {
+ return false
+ }
+ // Primary value is 0 and ignoreDiacritics is true. In this case we
+ // ignore the tertiary element, as it only pertains to the modifier.
+ return true
+ }
+ // TODO: further distinguish once we have the new implementation.
+ if !(m.ignoreWidth || m.ignoreCase) && e.Tertiary() > 0 {
+ return false
+ }
+ // TODO: we ignore the Quaternary level for now.
+ return true
+}
+
+// TODO: Use a Boyer-Moore-like algorithm (probably Sunday) for searching.
+
+func (p *Pattern) forwardSearch(it *colltab.Iter) (start, end int) {
+ for start := 0; it.Next(); it.Reset(start) {
+ nextStart := it.End()
+ if end := p.searchOnce(it); end != -1 {
+ return start, end
+ }
+ start = nextStart
+ }
+ return -1, -1
+}
+
+func (p *Pattern) anchoredForwardSearch(it *colltab.Iter) (start, end int) {
+ if it.Next() {
+ if end := p.searchOnce(it); end != -1 {
+ return 0, end
+ }
+ }
+ return -1, -1
+}
+
+// next advances to the next weight in a pattern. f must return one of the
+// weights of a collation element. next will advance to the first non-zero
+// weight and return this weight and true if it exists, or 0, false otherwise.
+func (p *Pattern) next(i *int, f func(colltab.Elem) int) (weight int, ok bool) {
+ for *i < len(p.ce) {
+ v := f(p.ce[*i])
+ *i++
+ if v != 0 {
+ // Skip successive ignorable values.
+ for ; *i < len(p.ce) && f(p.ce[*i]) == 0; *i++ {
+ }
+ return v, true
+ }
+ }
+ return 0, false
+}
+
+// TODO: remove this function once Elem is internal and Tertiary returns int.
+func tertiary(e colltab.Elem) int {
+ return int(e.Tertiary())
+}
+
+// searchOnce tries to match the pattern s.p at the text position i. s.buf needs
+// to be filled with collation elements of the first segment, where n is the
+// number of source bytes consumed for this segment. It will return the end
+// position of the match or -1.
+func (p *Pattern) searchOnce(it *colltab.Iter) (end int) {
+ var pLevel [4]int
+
+ m := p.m
+ for {
+ k := 0
+ for ; k < it.N; k++ {
+ if v := it.Elems[k].Primary(); v > 0 {
+ if w, ok := p.next(&pLevel[0], colltab.Elem.Primary); !ok || v != w {
+ return -1
+ }
+ }
+
+ if !m.ignoreDiacritics {
+ if v := it.Elems[k].Secondary(); v > 0 {
+ if w, ok := p.next(&pLevel[1], colltab.Elem.Secondary); !ok || v != w {
+ return -1
+ }
+ }
+ } else if it.Elems[k].Primary() == 0 {
+ // We ignore tertiary values of collation elements of the
+ // secondary level.
+ continue
+ }
+
+ // TODO: distinguish between case and width. This will be easier to
+ // implement after we moved to the new collation implementation.
+ if !m.ignoreWidth && !m.ignoreCase {
+ if v := it.Elems[k].Tertiary(); v > 0 {
+ if w, ok := p.next(&pLevel[2], tertiary); !ok || int(v) != w {
+ return -1
+ }
+ }
+ }
+ // TODO: check quaternary weight
+ }
+ it.Discard() // Remove the current segment from the buffer.
+
+ // Check for completion.
+ switch {
+ // If any of these cases match, we are not at the end.
+ case pLevel[0] < len(p.ce):
+ case !m.ignoreDiacritics && pLevel[1] < len(p.ce):
+ case !(m.ignoreWidth || m.ignoreCase) && pLevel[2] < len(p.ce):
+ default:
+ // At this point, both the segment and pattern has matched fully.
+ // However, the segment may still be have trailing modifiers.
+ // This can be verified by another call to next.
+ end = it.End()
+ if it.Next() && it.Elems[0].Primary() == 0 {
+ if !m.ignoreDiacritics {
+ return -1
+ }
+ end = it.End()
+ }
+ return end
+ }
+
+ // Fill the buffer with the next batch of collation elements.
+ if !it.Next() {
+ return -1
+ }
+ }
+}
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