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MIPv6: simplify fixed point degrees conversion 

* Simplify the conversion of degrees from 24 bit fixed point to a float.
  Avoids strict-aliasing warning by gcc 4.4.
* Add reference to RFC 6757.
* Correct spelling of 'convert' in degrees_convert_fixed_to_float().

Change-Id: Icb680d009fdd960e8668fa3020060799d6a74c2f
Reviewed-on: https://code.wireshark.org/review/5913
Reviewed-by: Alexis La Goutte <alexis.lagoutte@gmail.com>
Petri-Dish: Alexis La Goutte <alexis.lagoutte@gmail.com>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Michael Mann <mmann78@netscape.net>
This commit is contained in:
Luke Mewburn 2014-12-21 01:05:07 +11:00 committed by Michael Mann
parent 210aaf11ba
commit d7fd00de9f
1 changed files with 15 additions and 32 deletions
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47
epan/dissectors/packet-mip6.c
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@ -42,6 +42,7 @@
* RFC 5949, Fast Handovers for Proxy Mobile IPv6
* RFC 6275, Mobility Support in IPv6 (Obsoletes RFC 3775).
* RFC 6602, Bulk Binding Update Support for Proxy Mobile IPv6
* RFC 6757, Access Network Identifier (ANI) Option for Proxy Mobile IPv6
*
*/
@ -3105,46 +3106,28 @@ static const value_string mip6_opt_acc_net_id_sub_opt_op_id_type[] = {
{ 2, "Realm of the operator"},
{ 0, NULL}
};
static float degrees_covert_fixed_to_float(guint value)
{
guint mantissa=0,exponent=0, sign=0, position=0, mask = 1,*ptrNumber = NULL, i ;
float floatNumber =0;
ptrNumber = (guint *) &floatNumber;
if(!value)
static float degrees_convert_fixed_to_float(guint value)
{
if (!value)
return 0;
/* If negative number save sign bit and take 2' complement*/
if(value & 0x800000) /* Input value is 24 bit number*/
{
value -= 1;
value ^= -1;
sign = 1;
/*
* RFC 6757 section 3.1.2.
* two's complement, fixed point number with 9 whole bits
*/
/* If high bit of 24 bit number, process as negative number */
if (value & 0x800000) {
return ((float)(0x1000000 - value)) / -32768.0f;
} else {
return ((float)value) / 32768.0f;
}
/* Find position of left most 1*/
for(i=0;i<24;i++)
{
if(value & mask )
position = i;
mask = (mask << 1);
}
mantissa = (value << (32 - position - 8 -1));
mantissa &= 0x007FFFFF;
if(sign)
mantissa = (mantissa | 0x80000000);
exponent = (position - 15 +127) << 23;
*ptrNumber = (mantissa | exponent);/* club mantissa, exponent and sign*/
return floatNumber;
}
static void degrees_base_custom(gchar *str, guint degrees)
{
g_snprintf(str, ITEM_LABEL_LENGTH, "%f", degrees_covert_fixed_to_float(degrees) );
g_snprintf(str, ITEM_LABEL_LENGTH, "%f", degrees_convert_fixed_to_float(degrees) );
}
static void