Checking in vendor folder for ease of using go get.

vendor/golang.org/x/text/search/pattern.go

@@ -0,0 +1,155 @@
+// 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
+		}
+	}
+}