Patchwork [03/14] iov: add iov_cpy

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Submitter Michael S. Tsirkin
Date Sept. 24, 2012, 11:04 p.m.
Message ID <a2b6d7e7a1190474b61b054dc483d03ba5e09f4a.1348527749.git.mst@redhat.com>
Download mbox | patch
Permalink /patch/186597/
State New
Headers show

Comments

Michael S. Tsirkin - Sept. 24, 2012, 11:04 p.m.
Add API to copy part of iovec safely.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 iov.c | 23 +++++++++++++++++++++++
 iov.h |  9 +++++++++
 2 files changed, 32 insertions(+)
Anthony Liguori - Sept. 25, 2012, 12:34 a.m.
"Michael S. Tsirkin" <mst@redhat.com> writes:

> Add API to copy part of iovec safely.
>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
>  iov.c | 23 +++++++++++++++++++++++
>  iov.h |  9 +++++++++
>  2 files changed, 32 insertions(+)
>
> diff --git a/iov.c b/iov.c
> index c6a66f0..0dfcb28 100644
> --- a/iov.c
> +++ b/iov.c
> @@ -228,3 +228,26 @@ void iov_hexdump(const struct iovec *iov, const unsigned int iov_cnt,
>          fprintf(fp, "\n");
>      }
>  }
> +
> +unsigned iov_cpy(struct iovec *dst_iov, unsigned int dst_iov_cnt,
> +                 const struct iovec *iov, unsigned int iov_cnt,
> +                 size_t offset, size_t bytes)

I think the readability f the cde wuld be imprved if yu added the
missing 'o' to iov_cpy.

Otherwise:

Reviewed-by: Anthony Liguori <aliguori@us.ibm.com>

Regards,

Anthony Liguori

> +{
> +    size_t len;
> +    unsigned int i, j;
> +    for (i = 0, j = 0; i < iov_cnt && j < dst_iov_cnt && bytes; i++) {
> +        if (offset >= iov[i].iov_len) {
> +            offset -= iov[i].iov_len;
> +            continue;
> +        }
> +        len = MIN(bytes, iov[i].iov_len - offset);
> +
> +        dst_iov[j].iov_base = iov[i].iov_base + offset;
> +        dst_iov[j].iov_len = len;
> +        j++;
> +        bytes -= len;
> +        offset = 0;
> +    }
> +    assert(offset == 0);
> +    return j;
> +}
> diff --git a/iov.h b/iov.h
> index a73569f..f0daefa 100644
> --- a/iov.h
> +++ b/iov.h
> @@ -86,3 +86,12 @@ ssize_t iov_send_recv(int sockfd, struct iovec *iov, unsigned iov_cnt,
>   */
>  void iov_hexdump(const struct iovec *iov, const unsigned int iov_cnt,
>                   FILE *fp, const char *prefix, size_t limit);
> +
> +/*
> + * Partial copy of vector from iov to dst_iov (data is not copied).
> + * dst_iov overlaps iov at a specified offset.
> + * size of dst_iov is at most bytes. Actual size is returned.
> + */
> +size_t iov_cpy(struct iovec *dst_iov, unsigned int dst_iov_cnt,
> +               const struct iovec *iov, unsigned int iov_cnt,
> +               size_t offset, size_t bytes);
> -- 
> MST
Michael S. Tsirkin - Sept. 25, 2012, 12:45 a.m.
On Mon, Sep 24, 2012 at 07:34:00PM -0500, Anthony Liguori wrote:
> "Michael S. Tsirkin" <mst@redhat.com> writes:
> 
> > Add API to copy part of iovec safely.
> >
> > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > ---
> >  iov.c | 23 +++++++++++++++++++++++
> >  iov.h |  9 +++++++++
> >  2 files changed, 32 insertions(+)
> >
> > diff --git a/iov.c b/iov.c
> > index c6a66f0..0dfcb28 100644
> > --- a/iov.c
> > +++ b/iov.c
> > @@ -228,3 +228,26 @@ void iov_hexdump(const struct iovec *iov, const unsigned int iov_cnt,
> >          fprintf(fp, "\n");
> >      }
> >  }
> > +
> > +unsigned iov_cpy(struct iovec *dst_iov, unsigned int dst_iov_cnt,
> > +                 const struct iovec *iov, unsigned int iov_cnt,
> > +                 size_t offset, size_t bytes)
> 
> I think the readability f the cde wuld be imprved if yu added the
> missing 'o' to iov_cpy.

I was thinking about memcpy but maybe that's not a good model to follow.
Will fix.

> Otherwise:
> 
> Reviewed-by: Anthony Liguori <aliguori@us.ibm.com>
> 
> Regards,
> 
> Anthony Liguori
> 
> > +{
> > +    size_t len;
> > +    unsigned int i, j;
> > +    for (i = 0, j = 0; i < iov_cnt && j < dst_iov_cnt && bytes; i++) {
> > +        if (offset >= iov[i].iov_len) {
> > +            offset -= iov[i].iov_len;
> > +            continue;
> > +        }
> > +        len = MIN(bytes, iov[i].iov_len - offset);
> > +
> > +        dst_iov[j].iov_base = iov[i].iov_base + offset;
> > +        dst_iov[j].iov_len = len;
> > +        j++;
> > +        bytes -= len;
> > +        offset = 0;
> > +    }
> > +    assert(offset == 0);
> > +    return j;
> > +}
> > diff --git a/iov.h b/iov.h
> > index a73569f..f0daefa 100644
> > --- a/iov.h
> > +++ b/iov.h
> > @@ -86,3 +86,12 @@ ssize_t iov_send_recv(int sockfd, struct iovec *iov, unsigned iov_cnt,
> >   */
> >  void iov_hexdump(const struct iovec *iov, const unsigned int iov_cnt,
> >                   FILE *fp, const char *prefix, size_t limit);
> > +
> > +/*
> > + * Partial copy of vector from iov to dst_iov (data is not copied).
> > + * dst_iov overlaps iov at a specified offset.
> > + * size of dst_iov is at most bytes. Actual size is returned.
> > + */
> > +size_t iov_cpy(struct iovec *dst_iov, unsigned int dst_iov_cnt,
> > +               const struct iovec *iov, unsigned int iov_cnt,
> > +               size_t offset, size_t bytes);
> > -- 
> > MST

Patch

diff --git a/iov.c b/iov.c
index c6a66f0..0dfcb28 100644
--- a/iov.c
+++ b/iov.c
@@ -228,3 +228,26 @@  void iov_hexdump(const struct iovec *iov, const unsigned int iov_cnt,
         fprintf(fp, "\n");
     }
 }
+
+unsigned iov_cpy(struct iovec *dst_iov, unsigned int dst_iov_cnt,
+                 const struct iovec *iov, unsigned int iov_cnt,
+                 size_t offset, size_t bytes)
+{
+    size_t len;
+    unsigned int i, j;
+    for (i = 0, j = 0; i < iov_cnt && j < dst_iov_cnt && bytes; i++) {
+        if (offset >= iov[i].iov_len) {
+            offset -= iov[i].iov_len;
+            continue;
+        }
+        len = MIN(bytes, iov[i].iov_len - offset);
+
+        dst_iov[j].iov_base = iov[i].iov_base + offset;
+        dst_iov[j].iov_len = len;
+        j++;
+        bytes -= len;
+        offset = 0;
+    }
+    assert(offset == 0);
+    return j;
+}
diff --git a/iov.h b/iov.h
index a73569f..f0daefa 100644
--- a/iov.h
+++ b/iov.h
@@ -86,3 +86,12 @@  ssize_t iov_send_recv(int sockfd, struct iovec *iov, unsigned iov_cnt,
  */
 void iov_hexdump(const struct iovec *iov, const unsigned int iov_cnt,
                  FILE *fp, const char *prefix, size_t limit);
+
+/*
+ * Partial copy of vector from iov to dst_iov (data is not copied).
+ * dst_iov overlaps iov at a specified offset.
+ * size of dst_iov is at most bytes. Actual size is returned.
+ */
+size_t iov_cpy(struct iovec *dst_iov, unsigned int dst_iov_cnt,
+               const struct iovec *iov, unsigned int iov_cnt,
+               size_t offset, size_t bytes);