decoder.InputOffset() reports wrong result when having nested quotes

[AsafMah]

When decoding, it seems that the internal buffer stores the data without nested quotes, and its offsets seem to be reported for this buffer.

So the InputOffset() method will report the wrong offset compared to the original input and to encoding/json.

Example:

func TestDecode(t *testing.T) {
    dec := json.NewDecoder(bytes.NewReader([]byte(`{"test":"\""}`)))
    offset := dec.InputOffset()
    if offset != 0 {
        t.Errorf("expected 0, got %d", offset)
    }

    var v map[string]interface{}
    err := dec.Decode(&v)

    if err != nil {
        t.Errorf("unexpected error: %v", err)
    }

    if v["test"] != "\"" {
        t.Errorf("expected [\"a\",\"b\"], got %v", v["test"])
    }

    offset = dec.InputOffset()

    if offset != 13 {
        t.Errorf("expected offset to be 13, got %d", offset)
    }
}

When using encoding/json: passes

when using goccy/go-json: expected offset to be 13, got 12.

The discrepancy will get bigger the more nested quotes there are.