This commit updates `ContentReader::read` to optionally close the
underlying `Reader` when a message is read that does not terminate
the DAP header immediately following the `Content-Length` header
field.
This fixes an infinite loop when parsing an invalid DAP message. In
particular, the infinite loop occurs when a cross-site HTTP request from
a browser running on the same host as a cppdap server is sent to the
server. As cross-site requests to the localhost can be triggered by
untrusted JavaScript, more validation of the DAP messages is required to
protect cppdap-based servers from malicious requests.
This commit introduces a new enum flag on both `Session` and
`ContentReader` to allow a user to indicate that the underlying `Reader`
should be closed when an invalid DAP message is received. The
server example has been updated to indicate that invalid messages
should result in closure of the underlying `Reader`.
Per #115, `ContentReader::match` must block until the whole pattern is
read or the underlying `Reader` is closed. The previous commit reverted
the change from #50 to ensure this behavior is still implemented.
This commit re-adds the unit test from #50 with an update to the
behavior of `StringBuffer` to correct implement `Reader` so that
the partial read test case is still covered by the unit tests.
When there is partial message in reader, popping out the
characters lead to parse errors on the subsequent attempt
to parse. To avoid this, the last matched characters'
index is stored during parsing and reset on error.
