From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:34122) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fuLGN-00066e-LV for qemu-devel@nongnu.org; Mon, 27 Aug 2018 13:25:16 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fuLGJ-0001jE-RA for qemu-devel@nongnu.org; Mon, 27 Aug 2018 13:25:15 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:53324 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1fuLGG-0001SL-2w for qemu-devel@nongnu.org; Mon, 27 Aug 2018 13:25:11 -0400 References: <20180827070021.11931-1-armbru@redhat.com> <20180827070021.11931-7-armbru@redhat.com> From: Eric Blake Message-ID: <9f11e72b-42c5-da48-3f70-7370d680d59d@redhat.com> Date: Mon, 27 Aug 2018 12:25:02 -0500 MIME-Version: 1.0 In-Reply-To: <20180827070021.11931-7-armbru@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 6/6] json: Eliminate lexer state IN_WHITESPACE, pseudo-token JSON_SKIP List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Markus Armbruster , qemu-devel@nongnu.org Cc: marcandre.lureau@redhat.com, mdroth@linux.vnet.ibm.com On 08/27/2018 02:00 AM, Markus Armbruster wrote: > The lexer ignores whitespace like this: > > on whitespace on non-ws spontaneously > IN_START --> IN_WHITESPACE --> JSON_SKIP --> IN_START > ^ | > \__/ on whitespace > > This accumulates a whitespace token in state IN_WHITESPACE, only to > throw it away on the transition via JSON_SKIP to the start state. > Wasteful. Go from IN_START to IN_START on whitspace directly, s/whitspace/whitespace/ > dropping the whitespace character. > > Signed-off-by: Markus Armbruster > --- > qobject/json-lexer.c | 22 +++++----------------- > qobject/json-parser-int.h | 1 - > 2 files changed, 5 insertions(+), 18 deletions(-) > > @@ -263,10 +253,10 @@ static const uint8_t json_lexer[][256] = { > [','] = JSON_COMMA, > [':'] = JSON_COLON, > ['a' ... 'z'] = IN_KEYWORD, > - [' '] = IN_WHITESPACE, > - ['\t'] = IN_WHITESPACE, > - ['\r'] = IN_WHITESPACE, > - ['\n'] = IN_WHITESPACE, > + [' '] = IN_START, > + ['\t'] = IN_START, > + ['\r'] = IN_START, > + ['\n'] = IN_START, > }, > [IN_START_INTERP]['%'] = IN_INTERP, Don't you need to set [IN_START_INTERP][' '] to IN_START_INTERP, rather than IN_START? Otherwise, the presence of skipped whitespace would change whether interpolation happens. (At least, that's what you had in an earlier version of this patch). > }; > @@ -323,10 +313,8 @@ static void json_lexer_feed_char(JSONLexer *lexer, char ch, bool flush) > json_message_process_token(lexer, lexer->token, new_state, > lexer->x, lexer->y); > /* fall through */ > - case JSON_SKIP: > - g_string_truncate(lexer->token, 0); > - /* fall through */ > case IN_START: > + g_string_truncate(lexer->token, 0); > new_state = lexer->start_state; Oh, I see. We are magically reverting to the correct start state if the requested transition reports IN_START, rather than blindly using IN_START. Reviewed-by: Eric Blake -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org