Re: [Qemu-devel] [PATCH 2/4] qjson: do not save/restore contexts

[Eric Blake <eblake@redhat.com>]

[-- Attachment #1: Type: text/plain, Size: 1694 bytes --]

On 11/20/2015 02:04 AM, Paolo Bonzini wrote:
> JSON is LL(1) and our parser indeed needs only 1 token lookahead.
> Saving the parser context is mostly unnecessary; we can replace it
> with peeking at the next token, or remove it altogether when the
> restore only happens on errors.  The token list is destroyed anyway
> on errors.
> 
> The only interesting thing is that parse_keyword always eats
> a TOKEN_KEYWORD, even if it is invalid, so it must come last in
> parse_value (otherwise, NULL is returned, parse_literal is invoked
> and it tries to peek beyond end of input).  This is caught by
> /errors/unterminated/literal, which actually checks for an unterminated
> keyword. ಠ_ಠ
> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  qobject/json-parser.c | 59 ++++++++++++++++++---------------------------------
>  1 file changed, 21 insertions(+), 38 deletions(-)
> 

> @@ -578,17 +556,21 @@ out:
>  static QObject *parse_escape(JSONParserContext *ctxt, va_list *ap)
>  {
>      QObject *token = NULL, *obj;
> -    JSONParserContext saved_ctxt = parser_context_save(ctxt);
>  
>      if (ap == NULL) {
>          goto out;
>      }
>  
> -    token = parser_context_pop_token(ctxt);
> +    token = parser_context_peek_token(ctxt);
>      if (token == NULL) {
>          goto out;
>      }
>  
> +    if (token_get_type(token) != JSON_ESCAPE) {
> +        goto out;
> +    }

Could merge these two conditionals.

Otherwise, makes sense to me, and a lot less complicated.

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 604 bytes --]