This rewrites the json-parser to use a push parser aka state machine.
While push parsers are inherently more complex than recursive descent,
the grammar for JSON is simple enough that the parser remains readable.
There is therefore no need to use e.g. QEMU coroutines.
Unlike the suggestion in commit 62815d85aed ("json: Redesign the callback
to consume JSON values", 2018-08-24), I kept the json-streamer concept.
It helps in handling input limits, it performs error recovery, and it
converts the token-at-a-time push interface to callbacks---all things
that are more easily done in a separate layer to keep the parser clean.
However, there is no need anymore for it to store partial JSON objects
in tokenized form.
Another benefit is that QEMU can report the first parsing error
immediately, without waiting for delimiters to be balanced.
On top of the benefits intrinsic in the push architecture, it so happens
that it's really easy to add a location to JSON parsing errors now, so
do that as well.
Paolo
Paolo Bonzini (5):
json-parser: pass around lookahead token, constify
json-parser: replace with a push parser
json-streamer: remove token queue
json-streamer: do not heap-allocate JSONToken
json-parser: add location to JSON parsing errors
include/qobject/json-parser.h | 12 +-
qobject/json-parser-int.h | 13 +-
qobject/json-lexer.c | 11 +-
qobject/json-parser.c | 493 ++++++++++++++++------------------
qobject/json-streamer.c | 107 ++++----
5 files changed, 310 insertions(+), 326 deletions(-)
--
2.52.0
