On 08/14/2017 04:57 PM, Eduardo Habkost wrote: > The helper function will be useful when writing support code to > deal with device slot information. > > TODO: documentation is incomplete and unclear, needs to be > improved. > > Signed-off-by: Eduardo Habkost <ehabk...@redhat.com> > --- > include/qapi/util.h | 39 +++++++++++++++++++++++++++++ > qapi/qapi-util.c | 66 > ++++++++++++++++++++++++++++++++++++++++++++++++++ > tests/test-qapi-util.c | 53 ++++++++++++++++++++++++++++++++++++++++ > 3 files changed, 158 insertions(+) >
> +/** > + * qobject_compare: > + * > + * Compare the value of @a and @b. > + * > + * If @a and @b have the same type and the same value (see list > + * of supported types below), return 0. > + * > + * If @a and @b are both strings, return strcmp(a, b). > + * > + * If @a and @b are numbers, return a negative value if a < b, > + * and a positive value if a > b. > + * > + * Otherwise (if @a and @b are not the same, have different types, > + * are of an unsupported type, or are different), return a non-zero value. Is this number going to be commutative and distributive, in order to provide stable qsort()ing? That is, if comparing a and b gives a positive number, then comparing b and a should give a negative number; and if comparing a and b then b and c results in two positive numbers, then comparing a and c should also give a positive number. It is unclear from the documentation whether you are able to make this guarantee; and without it, it is unsafe to use this comparator in places that require stability. > + * > + * Note that this function doesn't support some types, and may > + * return false if the types are unsupported, or if the types don't > + * match exactly. How is a return of false (== 0, which also means equivalent) correct? > + * > + * Supported types: > + * - QTYPE_QNULL > + * - QTYPE_QSTRING > + * - QTYPE_QBOOL > + * - QTYPE_QNUM (integers only) > + * - QTYPE_QLIST > + * > + * Unsupported (always return false): > + * - QTYPE_QNUM (non-integer values) > + * - QTYPE_QDICT > + * > + * TODO: rewrite documentation to be clearer. > + * TODO: support non-integer QTYPE_NUM values and QTYPE_QDICT. There's another patch series pending for qobject_is_equal(); should these two patches share approaches or even code? https://lists.gnu.org/archive/html/qemu-devel/2017-07/msg01134.html https://lists.gnu.org/archive/html/qemu-devel/2017-08/msg02459.html -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org
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