Additional README for shellescape

Signed-off-by: Kimmo Lehto <[email protected]>

sh/shellescape/README.md

@@ -0,0 +1,57 @@
+# shellescape
+
+A drop-in replacement for [alessio/shellescape](https://github.com/alessio/shellescape) / ["gopkg.in/alessio/shellescape.v1"]("gopkg.in/alessio/shellescape.v1").
+
+It's a bit faster and allocates a little bit less. It's quite unlikely that anyone will notice any difference in a real-world application, the is here just to reduce dependencies of the `rig` package.
+
+To use, replace `alessio/shellescape` with `github.com/k0sproject/rig/v2/sh/shellescape` in your imports.
+
+## Benchmarks
+
+Just out of curiosity.
+
+### Quote
+
+```text
+BenchmarkQuote/#00-12                       382379658   3.037 ns/op     0 B/op    0 allocs/op
+BenchmarkQuote/"double_quoted"-12           14906526    79.10 ns/op    24 B/op    1 allocs/op
+BenchmarkQuote/with_spaces-12               16851456    71.15 ns/op    16 B/op    1 allocs/op
+BenchmarkQuote/'single_quoted'-12           8453859     154.4 ns/op    72 B/op    2 allocs/op
+BenchmarkQuote/;-12                         25321892    45.73 ns/op     3 B/op    1 allocs/op
+BenchmarkQuote/;${}-12                      22446418    54.00 ns/op     8 B/op    1 allocs/op
+BenchmarkQuote/foo.example.com-12           39565838    29.85 ns/op     0 B/op    0 allocs/op
+
+BenchmarkQuoteAlessio/#00-12                678336361   1.773 ns/op     0 B/op    0 allocs/op
+BenchmarkQuoteAlessio/"double_quoted"-12    10867801    129.4 ns/op    24 B/op    1 allocs/op
+BenchmarkQuoteAlessio/with_spaces-12        6283456     187.8 ns/op    16 B/op    1 allocs/op
+BenchmarkQuoteAlessio/'single_quoted'-12    6507007     180.3 ns/op    56 B/op    2 allocs/op
+BenchmarkQuoteAlessio/;-12                  11453983    163.8 ns/op     3 B/op    1 allocs/op
+BenchmarkQuoteAlessio/;${}-12               10179727    123.2 ns/op     8 B/op    1 allocs/op
+BenchmarkQuoteAlessio/foo.example.com-12    3416793     357.8 ns/op     0 B/op    0 allocs/op
+
+```
+
+### QuoteCommand
+
+```text
+BenchmarkQuoteCommand/Basic_Command-12            7548391       159.4 ns/op      88 B/op       2 allocs/op
+BenchmarkQuoteCommandAlessio/Basic_Command-12     2256212       572.1 ns/op      96 B/op       3 allocs/op
+```
+
+### StripUnsafe
+
+Looks like there isn't much difference between the two.
+
+```text
+BenchmarkStripUnsafe/Hello,_World!-12                        33246037    34.29 ns/op     0 B/op    0 allocs/op
+BenchmarkStripUnsafe/\x00\x01\x02Test\x03\x04\x05-12         16221404    71.40 ns/op    16 B/op    1 allocs/op
+BenchmarkStripUnsafe/SpecialChars\x1f\x7f-12                 10196348    113.1 ns/op    24 B/op    1 allocs/op
+BenchmarkStripUnsafe/中文测试-12                             14912823    79.82 ns/op     0 B/op    0 allocs/op
+BenchmarkStripUnsafe/#00-12                                  673622737   1.777 ns/op     0 B/op    0 allocs/op
+
+BenchmarkStripUnsafeAlessio/Hello,_World!-12                 24444872    48.44 ns/op     0 B/op    0 allocs/op
+BenchmarkStripUnsafeAlessio/\x00\x01\x02Test\x03\x04\x05-12  17340309    68.57 ns/op    16 B/op    1 allocs/op
+BenchmarkStripUnsafeAlessio/SpecialChars\x1f\x7f-12          13657556    80.99 ns/op    24 B/op    1 allocs/op
+BenchmarkStripUnsafeAlessio/中文测试-12                      13895878    85.13 ns/op     0 B/op    0 allocs/op
+BenchmarkStripUnsafeAlessio/#00-12                           473620983   2.509 ns/op     0 B/op    0 allocs/op
+```

sh/shellescape/shellescape.go

@@ -2,14 +2,13 @@
 //
 // It is a drop-in replacement for gopkg.in/alessio/shellescape.v1.
 //
-// There are no regular expressions and it avoids allocations by using a strings.Builder.
-//
-// Additionally an Unquote function is provider.
+// Additionally an Unquote function is provided.
 package shellescape
 
 import (
 	"strings"
 	"unicode"
+	"unicode/utf8"
 )
 
 // classify returns whether the string is empty, contains single quotes, or contains special characters.
@@ -43,14 +42,21 @@ func wrapTo(str string, builder *strings.Builder) {
 
 // wrap in single quotes and escape single quotes and backslashes.
 func escapeTo(str string, builder *strings.Builder) {
-	builder.Grow(len(str) + 3) // there will be at least 1 extra char and 2 quotes
+	builder.Grow(len(str) + 3) // there will be at least 1 extra char and 2 quotes - otherwise we wouldn't be here
 	builder.WriteByte('\'')
-	for _, c := range str {
+	for _, c := range str { //nolint:varnamelen
 		if c == '\'' {
+			builder.Grow(5) // quoting single quotes requires 4 extra chars
 			builder.WriteString(`'"'"'`)
 			continue
 		}
-		builder.WriteRune(c)
+		// According to strings.Map source code, this is faster than
+		// always using WriteRune.
+		if c < utf8.RuneSelf {
+			builder.WriteByte(byte(c))
+		} else {
+			builder.WriteRune(c)
+		}
 	}
 	builder.WriteByte('\'')
 }
@@ -126,18 +132,21 @@ func QuoteCommand(args []string) string {
 	return Join(args...)
 }
 
+func isPrint(r rune) rune {
+	if unicode.IsPrint(r) {
+		return r
+	}
+
+	return -1
+}
+
 // StripUnsafe removes non-printable runes from a string.
 func StripUnsafe(s string) string {
-	builder, ok := builderPool.Get().(*strings.Builder)
-	if !ok {
-		builder = &strings.Builder{}
-	}
-	defer builderPool.Put(builder)
-	defer builder.Reset()
 	for _, r := range s {
-		if unicode.IsPrint(r) {
-			builder.WriteRune(r)
+		if isPrint(r) == -1 {
+			// Avoid allocations by only stripping when the string contains non-printable runes.
+			return strings.Map(isPrint, s)
 		}
 	}
-	return builder.String()
+	return s
 }