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Resolve 424: Set (*Stream).bufSize equal to size of (*Stream).buf when it resized #428

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Resolve 424: Set (*Stream).bufSize equal to size of (*Stream).buf when it resized #428

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18 changes: 18 additions & 0 deletions decode_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -267,6 +267,24 @@ func Test_Decoder_UseNumber(t *testing.T) {
assertEq(t, "json.Number", "json.Number", fmt.Sprintf("%T", v["a"]))
}

func Test_Decoder_UnexpectedEnd(t *testing.T) {
input := []byte("\"000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe2\xe200")

dec := json.NewDecoder(bytes.NewReader(input))

for {
_, err := dec.Token()
if err != nil {
var e *json.SyntaxError
if errors.As(err, &e) {
assertEq(t, "error is not expected by test", e.Error(), "json: string unexpected end of JSON input")
break
}
t.Fatal(err)
}
}
}

func Test_Decoder_DisallowUnknownFields(t *testing.T) {
dec := json.NewDecoder(strings.NewReader(`{"x": 1}`))
dec.DisallowUnknownFields()
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1 change: 1 addition & 0 deletions internal/decoder/string.go
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Original file line number Diff line number Diff line change
Expand Up @@ -270,6 +270,7 @@ func stringBytes(s *Stream) ([]byte, error) {
r, size := utf8.DecodeRune(s.buf[cursor:])
if r == utf8.RuneError {
s.buf = append(append(append([]byte{}, s.buf[:cursor]...), runeErrBytes...), s.buf[cursor+1:]...)
s.bufSize = int64(len(s.buf))
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@vadiminshakov I would like some more explanation as to why the bufSize needs to be changed at this place

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We get panic here https://github.com/goccy/go-json/blob/master/internal/decoder/stream.go#L201

Panic occurs because the cursor is pointing out of bounds s.buf.
s.buf slice boundaries are set here: https://github.com/goccy/go-json/blob/master/internal/decoder/stream.go#L195)

But these boundaries do not match where the cursor is pointing. My change makes it so that the cursor does not go beyond the buffer bounds (on s.buf resize we change bufSize accordingly).

cursor += runeErrBytesLen
s.length += runeErrBytesLen
_, _, p = s.stat()
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