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Re: [Qemu-devel] [PATCH] qemu: json: Fix parsing of integers >= 0x800000
From: |
Daniel P. Berrange |
Subject: |
Re: [Qemu-devel] [PATCH] qemu: json: Fix parsing of integers >= 0x8000000000000000 |
Date: |
Mon, 23 May 2011 15:32:52 +0100 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Mon, May 23, 2011 at 04:29:55PM +0200, Markus Armbruster wrote:
> Anthony Liguori <address@hidden> writes:
>
> >>> The actual value of the alert will surprise you :-)
> >>>
> >>> Integers in Javascript are actually represented as doubles
> >>> internally which means that integer constants are only accurate up
> >>> to 52 bits.
> >>>
> >>> So really, we should cap integers at 32-bit :-/
> >>>
> >>> Have I mentioned recently that I really dislike JSON...
> >>
> >> NB, I am distinguishing between JSON the generic specification and
> >> JSON as implemented in web browsers. JSON the specification has *no*
> >> limitation on integers.
> >
> > The spec has no notion of integers at all. Here's the relevant
>
> It doesn't differentiate between integers and floating-point numbers
> *syntactically*. There are just numbers. Some of them happen to be
> integers.
>
> > text. Note that the BNF only has a single entry point for numbers. It
> > does not distinguish between integers and floating point numbers.
> > Also, the only discussion of valid numbers is about whether the number
> > can be represented as a rational number. I think the only way to read
> > the spec here is that *all* numbers are meant to be represented as
> > floating point numbers.
> >
> > Regards,
> >
> > Anthony Liguori
> >
> > 2.4. Numbers
> >
> > The representation of numbers is similar to that used in most
> > programming languages. A number contains an integer component that
> > may be prefixed with an optional minus sign, which may be followed by
> > a fraction part and/or an exponent part.
> >
> > Octal and hex forms are not allowed. Leading zeros are not allowed.
> >
> > A fraction part is a decimal point followed by one or more digits.
> >
> > An exponent part begins with the letter E in upper or lowercase,
> > which may be followed by a plus or minus sign. The E and optional
> > sign are followed by one or more digits.
> >
> > Numeric values that cannot be represented as sequences of digits
> > (such as Infinity and NaN) are not permitted.
>
> Therefore, the number 1234567890123456789 is permitted.
>
> >
> >
> > number = [ minus ] int [ frac ] [ exp ]
> >
> > decimal-point = %x2E ; .
> >
> > digit1-9 = %x31-39 ; 1-9
> >
> > e = %x65 / %x45 ; e E
> >
> > exp = e [ minus / plus ] 1*DIGIT
> >
> > frac = decimal-point 1*DIGIT
> >
> > int = zero / ( digit1-9 *DIGIT )
> >
> > minus = %x2D ; -
> >
> > plus = %x2B ; +
> >
> > zero = %x30 ; 0
>
> There's more:
>
> 4. Parsers
>
> A JSON parser transforms a JSON text into another representation. A
> JSON parser MUST accept all texts that conform to the JSON grammar.
> A JSON parser MAY accept non-JSON forms or extensions.
Incidentally, we should likely use the QMP capabilities handshake to
optionally enable parsing support for Infinity/-Infinity/NaN in QEMU
since that seems to be a common extension used[1].
Regards,
Daniel
[1] http://deron.meranda.us/python/comparing_json_modules/numbers
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- Re: [Qemu-devel] [PATCH] qemu: json: Fix parsing of integers >= 0x8000000000000000, (continued)
- Re: [Qemu-devel] [PATCH] qemu: json: Fix parsing of integers >= 0x8000000000000000, Markus Armbruster, 2011/05/23
- Re: [Qemu-devel] [PATCH] qemu: json: Fix parsing of integers >= 0x8000000000000000, Anthony Liguori, 2011/05/23
- Re: [Qemu-devel] [PATCH] qemu: json: Fix parsing of integers >= 0x8000000000000000, Luiz Capitulino, 2011/05/23
- Re: [Qemu-devel] [PATCH] qemu: json: Fix parsing of integers >= 0x8000000000000000, Anthony Liguori, 2011/05/23
- Re: [Qemu-devel] [PATCH] qemu: json: Fix parsing of integers >= 0x8000000000000000, Daniel P. Berrange, 2011/05/23
- Re: [Qemu-devel] [PATCH] qemu: json: Fix parsing of integers >= 0x8000000000000000, Markus Armbruster, 2011/05/23
- Re: [Qemu-devel] [PATCH] qemu: json: Fix parsing of integers >= 0x8000000000000000,
Daniel P. Berrange <=
- Re: [Qemu-devel] [PATCH] qemu: json: Fix parsing of integers >= 0x8000000000000000, Anthony Liguori, 2011/05/23
- Re: [Qemu-devel] [PATCH] qemu: json: Fix parsing of integers >= 0x8000000000000000, Richard W.M. Jones, 2011/05/23
- Re: [Qemu-devel] [PATCH] qemu: json: Fix parsing of integers >= 0x8000000000000000, Anthony Liguori, 2011/05/23
- Re: [Qemu-devel] [PATCH] qemu: json: Fix parsing of integers >= 0x8000000000000000, Richard W.M. Jones, 2011/05/23
- Re: [Qemu-devel] [PATCH] qemu: json: Fix parsing of integers >= 0x8000000000000000, Anthony Liguori, 2011/05/23
- Re: [Qemu-devel] [PATCH] qemu: json: Fix parsing of integers >= 0x8000000000000000, Daniel P. Berrange, 2011/05/23
- Re: [Qemu-devel] [PATCH] qemu: json: Fix parsing of integers >= 0x8000000000000000, Daniel P. Berrange, 2011/05/23
- Re: [Qemu-devel] [PATCH] qemu: json: Fix parsing of integers >= 0x8000000000000000, Markus Armbruster, 2011/05/23
- Re: [Qemu-devel] [PATCH] qemu: json: Fix parsing of integers >= 0x8000000000000000, Anthony Liguori, 2011/05/23
- Re: [Qemu-devel] [PATCH] qemu: json: Fix parsing of integers >= 0x8000000000000000, Markus Armbruster, 2011/05/24