btrfssum: Don't emit JSON strings that are too long

Split it, and wrap it in an array.

6 files changed, 119 insertions, 2 deletions

diff --git a/lib/btrfs/btrfssum/shortsum.go b/lib/btrfs/btrfssum/shortsum.go
index 490c40a..a3a6d11 100644
--- a/lib/btrfs/btrfssum/shortsum.go
+++ b/lib/btrfs/btrfssum/shortsum.go
@@ -11,6 +11,7 @@ import (
 	"git.lukeshu.com/go/lowmemjson"
 
 	"git.lukeshu.com/btrfs-progs-ng/lib/jsonutil"
+	"git.lukeshu.com/btrfs-progs-ng/lib/textui"
 )
 
 type ShortSum string
@@ -27,12 +28,12 @@ func (sum ShortSum) ToFullSum() CSum {
 }
 
 func (sum ShortSum) EncodeJSON(w io.Writer) error {
-	return jsonutil.EncodeHexString(w, sum)
+	return jsonutil.EncodeSplitHexString(w, sum, textui.Tunable(80))
 }
 
 func (sum *ShortSum) DecodeJSON(r io.RuneScanner) error {
 	var out strings.Builder
-	if err := jsonutil.DecodeHexString(r, &out); err != nil {
+	if err := jsonutil.DecodeSplitHexString(r, &out); err != nil {
 		return err
 	}
 	*sum = ShortSum(out.String())
diff --git a/lib/btrfs/btrfssum/shortsum_test.go b/lib/btrfs/btrfssum/shortsum_test.go
new file mode 100644
index 0000000..aa7849a
--- /dev/null
+++ b/lib/btrfs/btrfssum/shortsum_test.go
@@ -0,0 +1,66 @@
+// Copyright (C) 2023  Luke Shumaker <lukeshu@lukeshu.com>
+//
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+package btrfssum_test
+
+import (
+	"bytes"
+	"testing"
+
+	"git.lukeshu.com/go/lowmemjson"
+	"github.com/stretchr/testify/assert"
+
+	"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/btrfssum"
+)
+
+func TestShortSumEncodeJSON(t *testing.T) {
+	t.Parallel()
+	type TestCase struct {
+		InputSum   btrfssum.ShortSum
+		OutputJSON string
+	}
+	testcases := map[string]TestCase{
+		"short": {
+			InputSum:   "xyz",
+			OutputJSON: `"78797a"`,
+		},
+		"long": {
+			InputSum:   "0123456789abcdefghijklmnopqrstuvwxyz;:.,ABCDEFG",
+			OutputJSON: `["303132333435363738396162636465666768696a6b6c6d6e6f707172737475767778797a3b3a2e2c","41424344454647"]`,
+		},
+		"medium": { // exactly the maximum string length
+			InputSum:   "0123456789abcdefghijklmnopqrstuvwxyz;:.,",
+			OutputJSON: `"303132333435363738396162636465666768696a6b6c6d6e6f707172737475767778797a3b3a2e2c"`,
+		},
+	}
+	for tcName, tc := range testcases {
+		tc := tc
+		t.Run(tcName, func(t *testing.T) {
+			t.Parallel()
+
+			var jsonBuf bytes.Buffer
+			assert.NoError(t, lowmemjson.NewEncoder(&jsonBuf).Encode(tc.InputSum))
+			assert.Equal(t, tc.OutputJSON, jsonBuf.String())
+
+			var rtSum btrfssum.ShortSum
+			assert.NoError(t, lowmemjson.NewDecoder(&jsonBuf).DecodeThenEOF(&rtSum))
+			assert.Equal(t, tc.InputSum, rtSum)
+		})
+	}
+}
+
+func FuzzShortSumJSONFuzz(f *testing.F) {
+	f.Fuzz(func(t *testing.T, _inSum []byte) {
+		t.Logf("in = %q", _inSum)
+		inSum := btrfssum.ShortSum(_inSum)
+
+		var jsonBuf bytes.Buffer
+		assert.NoError(t, lowmemjson.NewEncoder(&jsonBuf).Encode(inSum))
+		t.Logf("json = %q", jsonBuf.Bytes())
+
+		var outSum btrfssum.ShortSum
+		assert.NoError(t, lowmemjson.NewDecoder(&jsonBuf).DecodeThenEOF(&outSum))
+		assert.Equal(t, inSum, outSum)
+	})
+}
diff --git a/lib/btrfs/btrfssum/testdata/fuzz/FuzzShortSumJSONFuzz/162fbf5f010234baa3e0f8c91825ebb8bce17b9ad8365ae1cad6977b4114d1ec b/lib/btrfs/btrfssum/testdata/fuzz/FuzzShortSumJSONFuzz/162fbf5f010234baa3e0f8c91825ebb8bce17b9ad8365ae1cad6977b4114d1ec
new file mode 100644
index 0000000..338adec
--- /dev/null
+++ b/lib/btrfs/btrfssum/testdata/fuzz/FuzzShortSumJSONFuzz/162fbf5f010234baa3e0f8c91825ebb8bce17b9ad8365ae1cad6977b4114d1ec
@@ -0,0 +1,2 @@
+go test fuzz v1
+[]byte("00000000000000000000000000000000000000000")
diff --git a/lib/btrfs/btrfssum/testdata/fuzz/FuzzShortSumJSONFuzz/b15b16f1ef330f9113455291780be2915cecf2bd1b7dbe2e3af0505f042751e8 b/lib/btrfs/btrfssum/testdata/fuzz/FuzzShortSumJSONFuzz/b15b16f1ef330f9113455291780be2915cecf2bd1b7dbe2e3af0505f042751e8
new file mode 100644
index 0000000..c9fd0e4
--- /dev/null
+++ b/lib/btrfs/btrfssum/testdata/fuzz/FuzzShortSumJSONFuzz/b15b16f1ef330f9113455291780be2915cecf2bd1b7dbe2e3af0505f042751e8
@@ -0,0 +1,2 @@
+go test fuzz v1
+[]byte("Z")
diff --git a/lib/btrfs/btrfssum/testdata/fuzz/FuzzShortSumJSONFuzz/fecd8dd05aeedabe b/lib/btrfs/btrfssum/testdata/fuzz/FuzzShortSumJSONFuzz/fecd8dd05aeedabe
new file mode 100644
index 0000000..66b87de
--- /dev/null
+++ b/lib/btrfs/btrfssum/testdata/fuzz/FuzzShortSumJSONFuzz/fecd8dd05aeedabe
@@ -0,0 +1,2 @@
+go test fuzz v1
+[]byte("\xb8")
diff --git a/lib/jsonutil/hex_string.go b/lib/jsonutil/hex_string.go
index 06970ce..3e0b154 100644
--- a/lib/jsonutil/hex_string.go
+++ b/lib/jsonutil/hex_string.go
@@ -40,3 +40,47 @@ func DecodeHexString(r io.RuneScanner, dst io.ByteWriter) error {
 	}
 	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)
+	})
+}