Re: [libvirt] [PATCH v3 02/31] util: Introduce virFileInData
On 05/16/2017 10:55 PM, John Ferlan wrote:
On 05/16/2017 10:03 AM, Michal Privoznik wrote:
> This function takes a FD and determines whether the current
> position is in data section or in a hole. In addition to that,
> it also determines how much bytes are there remaining till the
> current section ends.
>
> Signed-off-by: Michal Privoznik <mprivozn(a)redhat.com>
> ---
> src/libvirt_private.syms | 1 +
> src/util/virfile.c | 82 +++++++++++++++++++
> src/util/virfile.h | 4 +
> tests/virfiletest.c | 203 +++++++++++++++++++++++++++++++++++++++++++++++
> 4 files changed, 290 insertions(+)
>
> diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
> index bbe283529..4102a002b 100644
> --- a/src/libvirt_private.syms
> +++ b/src/libvirt_private.syms
> @@ -1628,6 +1628,7 @@ virFileGetHugepageSize;
> virFileGetMountReverseSubtree;
> virFileGetMountSubtree;
> virFileHasSuffix;
> +virFileInData;
> virFileIsAbsPath;
> virFileIsDir;
> virFileIsExecutable;
> diff --git a/src/util/virfile.c b/src/util/virfile.c
> index ea44a647c..5b10f9489 100644
> --- a/src/util/virfile.c
> +++ b/src/util/virfile.c
> @@ -3793,6 +3793,88 @@ virFileComparePaths(const char *p1, const char *p2)
> cleanup:
> VIR_FREE(res1);
> VIR_FREE(res2);
> +
> + return ret;
> +}
> +
> +
Still undocumented.
I know it got discussed a few times... I guess the odd thing I find
about "long long" is that all the stream mgmt lengths/sizes, etc. are
size_t. You also only test for smaller values only. Just saying...
That's true for areas where we need to address individual bytes in
buffers, e.g. virStreamRecv & virStreamSend. When it comes to file
offsets like in virStorageVolDownload and virStorageVolUpload we use ULL.
Please just add the function description *and* why a long long is being
used here. Also a brief summary of what's being done and of course that
lseek @cleanup:
How about this:
+/**
+ * virFileInData:
+ * @fd: file to check
+ * @inData: true if current position in the @fd is in data section
+ * @length: amount of bytes until the end of the current section
+ *
+ * With sparse files not every extent has to be physically stored on
+ * the disk. This results in so called data or hole sections. This
+ * functions checks whether the current position in the file @fd is
+ * in a data section (@inData = 1) or in a hole (@inData = 0). Also,
+ * it sets @length to match the number of bytes remaining until the
+ * end of the current section.
+ *
+ * As a special case, there is an implicit hole at the end of any
+ * file. In this case, the function sets @inData = 0, @length = 0.
+ *
+ * Upon its return, the position in the @fd is left unchanged, i.e.
+ * despite this function lseek()-ing back and forth it always
+ * restores the original position in the file.
+ *
+ * NB, @length is type of long long because it corresponds to off_t
+ * the best.
+ *
+ * Returns 0 on success,
+ * -1 otherwise.
+ */
Michal