Patchwork [RFC,08/13] range: add Range structure

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Submitter Michael S. Tsirkin
Date May 13, 2013, 8:01 p.m.
Message ID <87af80d75efe782e9edb47f214e0521f50a9cf56.1368474222.git.mst@redhat.com>
Download mbox | patch
Permalink /patch/243513/
State New
Headers show

Comments

Michael S. Tsirkin - May 13, 2013, 8:01 p.m.
Sometimes we need to pass ranges around, add a
handy structure for this purpose.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 include/qemu/range.h | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)
Peter Maydell - May 13, 2013, 8:20 p.m.
On 13 May 2013 21:01, Michael S. Tsirkin <mst@redhat.com> wrote:
> Sometimes we need to pass ranges around, add a
> handy structure for this purpose.
>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
>  include/qemu/range.h | 22 ++++++++++++++++++++++
>  1 file changed, 22 insertions(+)
>
> diff --git a/include/qemu/range.h b/include/qemu/range.h
> index 3502372..4bcd346 100644
> --- a/include/qemu/range.h
> +++ b/include/qemu/range.h
> @@ -1,6 +1,28 @@
>  #ifndef QEMU_RANGE_H
>  #define QEMU_RANGE_H
>
> +#include <inttypes.h>
> +
> +/*
> + * Operations on 64 address ranges.

missing "bit" ?

> + * Notes:
> + *   - ranges must not wrap around 0, but can include the last byte ~0x0LL.
> + *   - this can not represent a full 0 to ~0x0LL range.
> + */
> +
> +/* A structure representing a range of addresses. */
> +struct Range {
> +    uint64_t begin; /* First byte of the range, or 0 if empty. */
> +    uint64_t end;   /* 1 + the last byte. 0 if range empty or ends at ~0x0LL. */
> +};
> +typedef struct Range Range;
> +
> +/* verify that range is not empty and does not overlap */

Doesn't overlap what? Why isn't an empty range valid?
The struct definition above says it's OK.

> +static inline bool range_valid(struct Range *range)
> +{
> +    return range->begin + 1 <= range->end;
> +}

I note that memory.c defines its own concept of an AddrRange.

thanks
-- PMM
Michael S. Tsirkin - May 14, 2013, 7:55 a.m.
On Mon, May 13, 2013 at 09:20:08PM +0100, Peter Maydell wrote:
> On 13 May 2013 21:01, Michael S. Tsirkin <mst@redhat.com> wrote:
> > Sometimes we need to pass ranges around, add a
> > handy structure for this purpose.
> >
> > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > ---
> >  include/qemu/range.h | 22 ++++++++++++++++++++++
> >  1 file changed, 22 insertions(+)
> >
> > diff --git a/include/qemu/range.h b/include/qemu/range.h
> > index 3502372..4bcd346 100644
> > --- a/include/qemu/range.h
> > +++ b/include/qemu/range.h
> > @@ -1,6 +1,28 @@
> >  #ifndef QEMU_RANGE_H
> >  #define QEMU_RANGE_H
> >
> > +#include <inttypes.h>
> > +
> > +/*
> > + * Operations on 64 address ranges.
> 
> missing "bit" ?
> 
> > + * Notes:
> > + *   - ranges must not wrap around 0, but can include the last byte ~0x0LL.
> > + *   - this can not represent a full 0 to ~0x0LL range.
> > + */
> > +
> > +/* A structure representing a range of addresses. */
> > +struct Range {
> > +    uint64_t begin; /* First byte of the range, or 0 if empty. */
> > +    uint64_t end;   /* 1 + the last byte. 0 if range empty or ends at ~0x0LL. */
> > +};
> > +typedef struct Range Range;
> > +
> > +/* verify that range is not empty and does not overlap */
> 
> Doesn't overlap what?

I meant wrap around there.

> Why isn't an empty range valid?
> The struct definition above says it's OK.

Yes it's a bad name. Should be range_non_empty or something.

> > +{
> > +    return range->begin + 1 <= range->end;
> > +}
> 
> I note that memory.c defines its own concept of an AddrRange.
> 
> thanks
> -- PMM

Good point, maybe I'll reuse that or just use two 64 bit fields explicitly.

Patch

diff --git a/include/qemu/range.h b/include/qemu/range.h
index 3502372..4bcd346 100644
--- a/include/qemu/range.h
+++ b/include/qemu/range.h
@@ -1,6 +1,28 @@ 
 #ifndef QEMU_RANGE_H
 #define QEMU_RANGE_H
 
+#include <inttypes.h>
+
+/*
+ * Operations on 64 address ranges.
+ * Notes:
+ *   - ranges must not wrap around 0, but can include the last byte ~0x0LL.
+ *   - this can not represent a full 0 to ~0x0LL range.
+ */
+
+/* A structure representing a range of addresses. */
+struct Range {
+    uint64_t begin; /* First byte of the range, or 0 if empty. */
+    uint64_t end;   /* 1 + the last byte. 0 if range empty or ends at ~0x0LL. */
+};
+typedef struct Range Range;
+
+/* verify that range is not empty and does not overlap */
+static inline bool range_valid(struct Range *range)
+{
+    return range->begin + 1 <= range->end;
+}
+
 /* 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)