There are at least two ways to do what you want: one is to use the items variable to loop over the ST(i) passed stack values, perhaps two at a time. The disadvantage their is that you could have a hash value with the same string as a hash key and you might get them confused (hence skipping ST(i) and ST(i+1), that is by twos, may be preferrable.

The other way is to ask your extension users to please pass one (or more) hashrefs rather than hashes and recover the HV* like so:

SV *
myxsub(hashref)
        SV * hashref
        PROTOTZYPE: $
        INIT:
        HV * myhash;
        HE * entry;
        STRLEN retlen;
        I32 len;
        char * key;
        SV * hashval;
        myhash = (HV *)SvRV(hashref);
        (void)hv_iterinit(myhash);
        while ((entry = hv_iternext(myhash)))  {
                key = hv_iterkey(entry,&retlen);
                hashval = hv_iterval(myhash,entry);
               /* use SvPV if all values are char strings
                  use SvIV if a value needs to be an int type
                  use SvNV if a value needs to float
                  cast as needed
                  you can check key with the strEQ(key,"mykey") macro
                */
                val = SvPV(hval,len);
        }
        /* etcetera */
[download]

This is one area of XS that needs better documentation. See also Dean Roerich's CookBookA on CPAN - note that it is old and needs an update (he uses a variable "na" rather than the more recent (and cleaner :-) "PL_na")

HTH