vendor: initial vendor

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

vendor/vbom.ml/util/sortorder/README.md

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+## sortorder [![GoDoc](https://godoc.org/vbom.ml/util/sortorder?status.svg)](https://godoc.org/vbom.ml/util/sortorder)
+
+    import "vbom.ml/util/sortorder"
+
+Sort orders and comparison functions.

vendor/vbom.ml/util/sortorder/doc.go

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+// Package sortorder implements sort orders and comparison functions.
+//
+// Currently, it only implements so-called "natural order", where integers
+// embedded in strings are compared by value.
+package sortorder // import "vbom.ml/util/sortorder"

vendor/vbom.ml/util/sortorder/natsort.go

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+package sortorder
+
+// Natural implements sort.Interface to sort strings in natural order. This
+// means that e.g. "abc2" < "abc12".
+//
+// Non-digit sequences and numbers are compared separately. The former are
+// compared bytewise, while the latter are compared numerically (except that
+// the number of leading zeros is used as a tie-breaker, so e.g. "2" < "02")
+//
+// Limitation: only ASCII digits (0-9) are considered.
+type Natural []string
+
+func (n Natural) Len() int           { return len(n) }
+func (n Natural) Swap(i, j int)      { n[i], n[j] = n[j], n[i] }
+func (n Natural) Less(i, j int) bool { return NaturalLess(n[i], n[j]) }
+
+func isdigit(b byte) bool { return '0' <= b && b <= '9' }
+
+// NaturalLess compares two strings using natural ordering. This means that e.g.
+// "abc2" < "abc12".
+//
+// Non-digit sequences and numbers are compared separately. The former are
+// compared bytewise, while the latter are compared numerically (except that
+// the number of leading zeros is used as a tie-breaker, so e.g. "2" < "02")
+//
+// Limitation: only ASCII digits (0-9) are considered.
+func NaturalLess(str1, str2 string) bool {
+	idx1, idx2 := 0, 0
+	for idx1 < len(str1) && idx2 < len(str2) {
+		c1, c2 := str1[idx1], str2[idx2]
+		dig1, dig2 := isdigit(c1), isdigit(c2)
+		switch {
+		case dig1 != dig2: // Digits before other characters.
+			return dig1 // True if LHS is a digit, false if the RHS is one.
+		case !dig1: // && !dig2, because dig1 == dig2
+			// UTF-8 compares bytewise-lexicographically, no need to decode
+			// codepoints.
+			if c1 != c2 {
+				return c1 < c2
+			}
+			idx1++
+			idx2++
+		default: // Digits
+			// Eat zeros.
+			for ; idx1 < len(str1) && str1[idx1] == '0'; idx1++ {
+			}
+			for ; idx2 < len(str2) && str2[idx2] == '0'; idx2++ {
+			}
+			// Eat all digits.
+			nonZero1, nonZero2 := idx1, idx2
+			for ; idx1 < len(str1) && isdigit(str1[idx1]); idx1++ {
+			}
+			for ; idx2 < len(str2) && isdigit(str2[idx2]); idx2++ {
+			}
+			// If lengths of numbers with non-zero prefix differ, the shorter
+			// one is less.
+			if len1, len2 := idx1-nonZero1, idx2-nonZero2; len1 != len2 {
+				return len1 < len2
+			}
+			// If they're equal, string comparison is correct.
+			if nr1, nr2 := str1[nonZero1:idx1], str2[nonZero2:idx2]; nr1 != nr2 {
+				return nr1 < nr2
+			}
+			// Otherwise, the one with less zeros is less.
+			// Because everything up to the number is equal, comparing the index
+			// after the zeros is sufficient.
+			if nonZero1 != nonZero2 {
+				return nonZero1 < nonZero2
+			}
+		}
+		// They're identical so far, so continue comparing.
+	}
+	// So far they are identical. At least one is ended. If the other continues,
+	// it sorts last.
+	return len(str1) < len(str2)
+}