Adding upstream version 2.5.1.

Signed-off-by: Daniel Baumann <daniel@debian.org>

search/levenshtein.go

@@ -0,0 +1,118 @@
+//  Copyright (c) 2014 Couchbase, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// 		http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package search
+
+import (
+	"math"
+)
+
+func LevenshteinDistance(a, b string) int {
+	la := len(a)
+	lb := len(b)
+	d := make([]int, la+1)
+	var lastdiag, olddiag, temp int
+
+	for i := 1; i <= la; i++ {
+		d[i] = i
+	}
+	for i := 1; i <= lb; i++ {
+		d[0] = i
+		lastdiag = i - 1
+		for j := 1; j <= la; j++ {
+			olddiag = d[j]
+			min := d[j] + 1
+			if (d[j-1] + 1) < min {
+				min = d[j-1] + 1
+			}
+			if a[j-1] == b[i-1] {
+				temp = 0
+			} else {
+				temp = 1
+			}
+			if (lastdiag + temp) < min {
+				min = lastdiag + temp
+			}
+			d[j] = min
+			lastdiag = olddiag
+		}
+	}
+	return d[la]
+}
+
+// LevenshteinDistanceMax same as LevenshteinDistance but
+// attempts to bail early once we know the distance
+// will be greater than max
+// in which case the first return val will be the max
+// and the second will be true, indicating max was exceeded
+func LevenshteinDistanceMax(a, b string, max int) (int, bool) {
+	v, wasMax, _ := LevenshteinDistanceMaxReuseSlice(a, b, max, nil)
+	return v, wasMax
+}
+
+func LevenshteinDistanceMaxReuseSlice(a, b string, max int, d []int) (int, bool, []int) {
+	la := len(a)
+	lb := len(b)
+
+	ld := int(math.Abs(float64(la - lb)))
+	if ld > max {
+		return max, true, d
+	} else if la == 0 || lb == 0 {
+		// if one string of the two strings is empty, then ld is
+		// the length of the other string and as such is <= max
+		return ld, false, d
+	}
+
+	if cap(d) < la+1 {
+		d = make([]int, la+1)
+	}
+	d = d[:la+1]
+
+	var lastdiag, olddiag, temp int
+
+	for i := 1; i <= la; i++ {
+		d[i] = i
+	}
+	for i := 1; i <= lb; i++ {
+		d[0] = i
+		lastdiag = i - 1
+		rowmin := max + 1
+		for j := 1; j <= la; j++ {
+			olddiag = d[j]
+			min := d[j] + 1
+			if (d[j-1] + 1) < min {
+				min = d[j-1] + 1
+			}
+			if a[j-1] == b[i-1] {
+				temp = 0
+			} else {
+				temp = 1
+			}
+			if (lastdiag + temp) < min {
+				min = lastdiag + temp
+			}
+			if min < rowmin {
+				rowmin = min
+			}
+			d[j] = min
+
+			lastdiag = olddiag
+		}
+		// after each row if rowmin isn't less than max stop
+		if rowmin > max {
+			return max, true, d
+		}
+	}
+	return d[la], false, d
+}