1 files changed, 86 insertions, 0 deletions
diff --git a/lib/jsonutil/hex_string.go b/lib/jsonutil/hex_string.go
new file mode 100644
index 0000000..3e0b154
--- /dev/null
+++ b/lib/jsonutil/hex_string.go
@@ -0,0 +1,86 @@
+// Copyright (C) 2023  Luke Shumaker <lukeshu@lukeshu.com>
+//
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+// Package jsonutil provides utilities for implementing the interfaces
+// consumed by the "git.lukeshu.com/go/lowmemjson" package.
+package jsonutil
+
+import (
+	"io"
+
+	"git.lukeshu.com/go/lowmemjson"
+)
+
+func EncodeHexString[T ~[]byte | ~string](w io.Writer, str T) error {
+	const hextable = "0123456789abcdef"
+	var buf [2]byte
+	buf[0] = '"'
+	if _, err := w.Write(buf[:1]); err != nil {
+		return err
+	}
+	for i := 0; i < len(str); i++ {
+		buf[0] = hextable[str[i]>>4]
+		buf[1] = hextable[str[i]&0x0f]
+		if _, err := w.Write(buf[:]); err != nil {
+			return err
+		}
+	}
+	buf[0] = '"'
+	if _, err := w.Write(buf[:1]); err != nil {
+		return err
+	}
+	return nil
+}
+
+func DecodeHexString(r io.RuneScanner, dst io.ByteWriter) error {
+	dec := &hexDecoder{dst: dst}
+	if err := lowmemjson.DecodeString(r, dec); err != nil {
+		return err
+	}
+	return dec.Close()
+}
+
+func EncodeSplitHexString[T ~[]byte | ~string](w io.Writer, str T, maxStrLen int) error {
+	if maxStrLen <= 0 || len(str) <= maxStrLen/2 {
+		return EncodeHexString(w, str)
+	}
+	var buf [1]byte
+	buf[0] = '['
+	if _, err := w.Write(buf[:]); err != nil {
+		return err
+	}
+	for len(str) > maxStrLen/2 {
+		if err := EncodeHexString(w, str[:maxStrLen/2]); err != nil {
+			return err
+		}
+		str = str[maxStrLen/2:]
+		if len(str) > 0 {
+			buf[0] = ','
+			if _, err := w.Write(buf[:]); err != nil {
+				return err
+			}
+		}
+	}
+	if len(str) > 0 {
+		if err := EncodeHexString(w, str); err != nil {
+			return err
+		}
+	}
+	buf[0] = ']'
+	if _, err := w.Write(buf[:]); err != nil {
+		return err
+	}
+	return nil
+}
+
+func DecodeSplitHexString(r io.RuneScanner, dst io.ByteWriter) error {
+	c, _, _ := r.ReadRune()
+	_ = r.UnreadRune()
+	if c == '"' {
+		return DecodeHexString(r, dst)
+	}
+	return lowmemjson.DecodeArray(r, func(r io.RuneScanner) error {
+		return DecodeHexString(r, dst)
+	})
+}