WIP: K/V line.

kvline.go

@@ -0,0 +1,87 @@
+package pt
+
+import (
+	"bytes"
+	"fmt"
+	"sort"
+	"unicode"
+)
+
+func kvline_value_needs_escape(input string) bool {
+	for _, c := range input {
+		if c == '\'' || c == '"' || !unicode.IsPrint(c) || unicode.IsSpace(c) {
+			return true
+		}
+	}
+
+	return false
+}
+
+func kvline_escape_value(input string) string {
+	if !kvline_value_needs_escape(input) {
+		return input
+	}
+
+	// This code could benefit from the strings.Builder, but we cannot use that
+	// because we want to work on Debian releases that have older Go versions.
+	var result bytes.Buffer
+
+	// Worst case all characters needs to be escaped.
+	result.Grow(2 * len(input))
+
+	for _, c := range input {
+		switch c {
+		case '\'':
+			result.WriteRune('\\')
+			result.WriteRune('\'')
+		case '"':
+			result.WriteRune('\\')
+			result.WriteRune('"')
+		case '\n':
+			result.WriteRune('\\')
+			result.WriteRune('n')
+		case '\t':
+			result.WriteRune('\\')
+			result.WriteRune('t')
+		case '\r':
+			result.WriteRune('\\')
+			result.WriteRune('r')
+		default:
+			result.WriteRune(c)
+		}
+	}
+
+	return fmt.Sprintf("\"%s\"", result.String())
+}
+
+func kvline_encode(input map[string]string) string {
+	// We need to make sure our ordering is stable. Go's map's are for sensible
+	// reasons non-stable.
+	keys := make([]string, 0, len(input))
+
+	for key := range input {
+		keys = append(keys, key)
+	}
+
+	sort.Strings(keys)
+
+	// This code could be refactored into using Go 1.10+ `strings.Builder`
+	// type, but for now we can perfectly fine with the additional allocated
+	// done by doing `+=` on strings :-)
+	var result string
+
+	for index := range keys {
+		key := keys[index]
+		value := input[key]
+
+		// Are we not the first iteration we need to add a space.
+		if index != 0 {
+			result += " "
+		}
+
+		result += fmt.Sprintf("%s=%s",
+			key, kvline_escape_value(value))
+	}
+
+	return result
+}

kvline_test.go

@@ -0,0 +1,24 @@
+package pt
+
+import (
+	"testing"
+)
+
+func TestKVLineEncoder(t *testing.T) {
+	tests := [...]struct {
+		value    map[string]string
+		expected string
+	}{
+		{map[string]string{"A": "B", "CD": "EF"}, "A=B CD=EF"},
+		{map[string]string{"AB": "C", "CDE": "F G"}, "AB=C CDE=\"F G\""},
+		{map[string]string{"A": "Foo Bar Baz\r\t\n\"'"}, "A=\"Foo Bar Baz\\r\\t\\n\\\"\\'\""},
+	}
+
+	for _, input := range tests {
+		encoded := kvline_encode(input.value)
+		if input.expected != encoded {
+			t.Errorf("kvline_encode(%v) → \"%v\" (expected \"%v\")",
+				input.value, encoded, input.expected)
+		}
+	}
+}