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From: | Anthony Liguori |
Subject: | Re: [Qemu-devel] [PATCH] qemu: json: Fix parsing of integers >= 0x8000000000000000 |
Date: | Mon, 23 May 2011 08:50:55 -0500 |
User-agent: | Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.17) Gecko/20110424 Lightning/1.0b2 Thunderbird/3.1.10 |
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 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. 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
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