Re: [libvirt] [PATCH v2 1/4] util: new function virFileLength()
On 11/20/2016 11:01 PM, Laine Stump wrote:
This new function just calls stat() and returns st_size (or -1 if
there is an error). We may decide we want this function to be more
complex, and handle things like block devices - this is a placeholder
(that works) for any more complicated funtion.
NB: virFileLength() takes a path rather than an fd because it needs to
be called for files that can't be opened (due to permissions).
I almost wonder if it would be better to take both a path AND an fd,
with semantics of:
if fd == -1, use path alone - stat()
if fd >= 0, path should be non-NULL and describes the fd (for error
messages) - fstat()
For block devices, [f]stat() probably won't do what we want, where
lseek(SEEK_END) and/or ioctl() may be better. But like you say, those
can be added later.
I definitely like the idea of having a nice wrapper function that we can
enhance later, to abstract out the logic so that it is not repeated in
the callers.
---
New in "V2"
src/libvirt_private.syms | 1 +
src/util/virfile.c | 13 +++++++++++++
src/util/virfile.h | 2 ++
3 files changed, 16 insertions(+)
+
+off_t
+virFileLength(const char *file)
+{
+ struct stat s;
+
+ if (stat(file, &s) < 0)
+ return -1;
+
+ return s.st_size;
Since we KNOW it won't work right on block devices, and we have the
stat() results, shouldn't this also check for S_ISREG(s.st_mode) and
return -1 if not?
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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