1 files changed, 28 insertions, 4 deletions
diff --git a/encode_escape.go b/encode_escape.go
index ab0d9c1..97da6e9 100644
--- a/encode_escape.go
+++ b/encode_escape.go
@@ -5,7 +5,10 @@
 package lowmemjson
 
 import (
+	"fmt"
 	"unicode/utf8"
+
+	"git.lukeshu.com/go/lowmemjson/internal/jsonstring"
 )
 
 // BackslashEscapeMode identifies one of the three ways that a
@@ -17,14 +20,35 @@ import (
 //     single-character)
 //
 //   - as a long Unicode `\uXXXX` backslash sequence
-type BackslashEscapeMode uint8
+type BackslashEscapeMode = jsonstring.BackslashEscapeMode
 
 const (
-	BackslashEscapeNone BackslashEscapeMode = iota
-	BackslashEscapeShort
-	BackslashEscapeUnicode
+	BackslashEscapeNone    = jsonstring.BackslashEscapeNone
+	BackslashEscapeShort   = jsonstring.BackslashEscapeShort
+	BackslashEscapeUnicode = jsonstring.BackslashEscapeUnicode
 )
 
+func hexToInt(c byte) rune {
+	switch {
+	case '0' <= c && c <= '9':
+		return rune(c) - '0'
+	case 'a' <= c && c <= 'f':
+		return rune(c) - 'a' + 10
+	case 'A' <= c && c <= 'F':
+		return rune(c) - 'A' + 10
+	default:
+		panic(fmt.Errorf("should not happen: invalid hex char: %q", c))
+	}
+}
+
+func hexToRune(a, b, c, d byte) rune {
+	return 0 |
+		hexToInt(a)<<12 |
+		hexToInt(b)<<8 |
+		hexToInt(c)<<4 |
+		hexToInt(d)<<0
+}
+
 // A BackslashEscaper controls how a ReEncoder emits a character in a
 // JSON string.  The `rune` argument is the character being
 // considered, and the `BackslashEscapeMode` argument is how it was