Re: [Qemu-devel] [PATCH 7/9] asn1_input-visitor.diff

[Stefan Berger <stefanb@linux.vnet.ibm.com>]

On 03/13/2013 04:51 PM, Eric Blake wrote:
> On 03/12/2013 09:09 PM, Joel Schopp wrote:
>> Implement an input visitor for ASN.1 BER encoding.
>>
>> Cc: Michael Tsirkin <mst@redhat.com>
>> Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
>> Signed-off-by: Joel Schopp <jschopp@linux.vnet.ibm.com>
>> ---
>>   include/qapi/ber-input-visitor.h |   30 ++
>>   qapi/Makefile.objs               |    2 +-
>>   qapi/ber-input-visitor.c         | 1073 ++++++++++++++++++++++++++++++++++++++
>>   3 files changed, 1104 insertions(+), 1 deletion(-)
>>   create mode 100644 include/qapi/ber-input-visitor.h
>>   create mode 100644 qapi/ber-input-visitor.c
>>
>> diff --git a/include/qapi/ber-input-visitor.h b/include/qapi/ber-input-visitor.h
>> new file mode 100644
>> index 0000000..eaa3d0e
>> --- /dev/null
>> +++ b/include/qapi/ber-input-visitor.h
>> @@ -0,0 +1,30 @@
>> +/*
>> + * BER Input Visitor header
>> + *
>> + * Copyright IBM, Corp. 2011
> It's 2013
>
>
>> +static void ber_input_type_number(Visitor *v, double *obj, const char *name,
>> +                                  Error **errp)
>> +{
>> +    BERInputVisitor *aiv = to_biv(v);
>> +    uint32_t ber_type_tag;
>> +    uint8_t ber_type_flags;
>> +    uint32_t len;
>> +    bool is_indefinite;
>> +    char buf[128], buf2[128];
>> +    GDoubleIEEE754 num;
>> +    struct ieee754_buffer number;
>> +    size_t to_read;
>> +
>> +    switch (number.first) {
>> +    case 0x42:
>> +        *obj = nan("NAN");
>> +        break;
>> +    case 0x41:
>> +    case 0x40:
>> +        num.mpn.sign = ((number.first & 0x1) != 0);
>> +        num.mpn.biased_exponent = ~0;
>> +        num.mpn.mantissa_low = 0;
>> +        num.mpn.mantissa_high = 0;
>> +        *obj = num.v_double;
> Is this really portable enough?  In other words, do we really require
> that qemu only compiles on platforms where double is in IEEE format?
>
Good question. I don't know in what format the other platforms are, 
though. I know it's used on i386, x86_64, ppc, ppc64. My guess is that 
it would have to be a really exotic CPU to not use this standard.

I hope this applies to ARM in general...
http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0067d/Cihgejjg.html

Regards,
     Stefan



     Stefan