Add package shell.

Handle POSIX style shell splitting and quotation.

LICENSE

@@ -1,6 +1,6 @@
 BSD 3-Clause License
 
-Copyright (C) 2016, Michael J. Fromberger
+Copyright (C) 2015 and on, Michael J. Fromberger
 All Rights Reserved.
 
 Redistribution and use in source and binary forms, with or without

README.md

@@ -23,4 +23,5 @@ This repository defines generic data structures in Go.
 - [mdiff](./mdiff) supports creating textual diffs ([package docs](https://godoc.org/github.com/creachadair/mds/mdiff), [example](https://go.dev/play/p/DFL6f7WLcff))
 - [mstr](./mstr) helpful functions for manipulating strings ([package docs](https://godoc.org/github.com/creachadair/mds/mstr))
 - [mtest](./mtest) a support library for writing tests ([package docs](https://godoc.org/github.com/creachadair/mds/mtest))
+- [shell](./shell) POSIX shell quoting and splitting ([package docs](https://godoc.org/github.com/creachadair/mds/shell))
 - [value](./value) helpful functions for basic values and pointers ([package docs](https://godoc.org/github.com/creachadair/mds/value))

shell/bench_test.go

@@ -0,0 +1,79 @@
+// Copyright (c) 2015, Michael J. Fromberger
+
+package shell_test
+
+import (
+	"bytes"
+	"fmt"
+	"math"
+	"math/rand"
+	"strings"
+	"testing"
+
+	"github.com/creachadair/mds/shell"
+)
+
+var input string
+
+// Generate a long random string with balanced quotations for perf testing.
+func init() {
+	var buf bytes.Buffer
+
+	src := rand.NewSource(12345)
+	r := rand.New(src)
+
+	const alphabet = "abcdefghijklmnopqrstuvwxyz0123456789   \t\n\n\n"
+	pick := func(f float64) byte {
+		pos := math.Ceil(f*float64(len(alphabet))) - 1
+		return alphabet[int(pos)]
+	}
+
+	const inputLen = 100000
+	var quote struct {
+		q byte
+		n int
+	}
+	for i := 0; i < inputLen; i++ {
+		if quote.n == 0 {
+			q := r.Float64()
+			if q < .1 {
+				quote.q = '"'
+				quote.n = r.Intn(256)
+				buf.WriteByte('"')
+				continue
+			} else if q < .15 {
+				quote.q = '\''
+				quote.n = r.Intn(256)
+				buf.WriteByte('\'')
+				continue
+			}
+		}
+		buf.WriteByte(pick(r.Float64()))
+		if quote.n > 0 {
+			quote.n--
+			if quote.n == 0 {
+				buf.WriteByte(quote.q)
+			}
+		}
+	}
+	input = buf.String()
+}
+
+func BenchmarkSplit(b *testing.B) {
+	var lens []int
+	for i := 1; i < len(input); i *= 4 {
+		lens = append(lens, i)
+	}
+	lens = append(lens, len(input))
+
+	b.ResetTimer()
+	for _, n := range lens {
+		b.Run(fmt.Sprintf("len_%d", n), func(b *testing.B) {
+			for i := 0; i < b.N; i++ {
+				shell.NewScanner(strings.NewReader(input[:n])).Each(ignore)
+			}
+		})
+	}
+}
+
+func ignore(string) bool { return true }