[Qemu-devel] Re: ANN: QEMU Monitor Protocol git tree

[Paolo Bonzini <bonzini@gnu.org>]

On 09/23/2009 12:57 PM, Avi Kivity wrote:
> On 09/23/2009 12:57 PM, Daniel P. Berrange wrote:
>>> Ignoring the dos-ism, since you can parse JSON with a regexp, why do we
>>> need explicit message boundaries?
>> I think it would be nice to be able to assume that each JSON message
>> will not cross a line-end boundary. Whether we use CRLF, just CR or
>> just LF I don't mind. Its much easier to search for a message boundary
>> by just doing strchr('\n') than having to actually parse the JSON or
>> use a regexp at that point.
>
> A good parser will consume exactly enough characters to make up an
> object or let you know if it needs more. I don't think using a regexp is
> warranted.

Agreed, regexes are unnecessary.  Also because a regex cannot parse 
JSON; it can only detect _some_ invalid JSON inputs, and then only if 
you're given an already complete input.

In other words, there are Javascript JSON parsers that are just "match a 
regexp and run eval on the input", but the actual parsing is done by the 
Javascript interpreter using eval.  The regexp is just avoiding the 
security problems that are inherent in eval.

Paolo