[Qemu-devel] Re: [PATCH V6 25/32] pci: add helper functions to check ranges overlap.

["Michael S. Tsirkin" <mst@redhat.com>]

On Fri, Oct 30, 2009 at 09:21:19PM +0900, Isaku Yamahata wrote:
> add helper function to check ranges overlap suggested by
> Michael S. Tsirkin <mst@redhat.com>.
> His original suggestion was to use [first, last], however I chosen
> to use offset, length pair, i.e. [offset, offset + length)
> because pci configuration space related functions all uses offset and length
> pair, so it helps to avoid to type constant twice.
> 
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>

Acked-by: Michael S. Tsirkin <mst@redhat.com>

> ---
>  hw/pci.h |   29 +++++++++++++++++++++++++++++
>  1 files changed, 29 insertions(+), 0 deletions(-)
> 
> diff --git a/hw/pci.h b/hw/pci.h
> index 8e5d64a..7991bfd 100644
> --- a/hw/pci.h
> +++ b/hw/pci.h
> @@ -406,4 +406,33 @@ PCIBus *pci_apb_init(target_phys_addr_t special_base,
>  PCIBus *sh_pci_register_bus(pci_set_irq_fn set_irq, pci_map_irq_fn map_irq,
>                              void *pic, int devfn_min, int nirq);
>  
> +/* These are not pci specific. Should move into a separate header.
> + * Only pci.c uses them, so keep them here for now.
> + */
> +
> +/* Get last byte of a range from offset + length.
> + * Undefined for ranges that wrap around 0. */
> +static inline uint64_t range_get_last(uint64_t offset, uint64_t len)
> +{
> +    return offset + len - 1;
> +}
> +
> +/* Check whether a given range covers a given byte. */
> +static inline int range_covers_byte(uint64_t offset, uint64_t len,
> +                                    uint64_t byte)
> +{
> +    return offset <= byte && byte <= range_get_last(offset, len);
> +}
> +
> +/* Check whether 2 given ranges overlap.
> + * Undefined if ranges that wrap around 0. */
> +static inline int ranges_overlap(uint64_t first1, uint64_t len1,
> +                                 uint64_t first2, uint64_t len2)
> +{
> +    uint64_t last1 = range_get_last(first1, len1);
> +    uint64_t last2 = range_get_last(first2, len2);
> +
> +    return !(last2 < first1 || last1 < first2);
> +}
> +
>  #endif
> -- 
> 1.6.0.2