On 07/03/2018 01:08 AM, Michal Prívozník wrote:
On 07/03/2018 01:18 AM, John Ferlan wrote:
On 06/29/2018 11:01 AM, Michal Privoznik wrote:
Firstly, we can utilize virCommandSetOutputBuffer() API which will collect the command output for us. Secondly, sscanf()-ing through each line is easier to understand (and more robust) than jumping over a string with strchr().
Signed-off-by: Michal Privoznik <mprivozn@redhat.com> --- src/util/viriscsi.c | 85 +++++++++++++++++++++-------------------------------- 1 file changed, 34 insertions(+), 51 deletions(-)
I assume virCommandSetOutputBuffer didn't exist when this code was created.
Perhaps. Let me check git log. .. .. And yes, you are right. virCommandSetOutputBuffer was introduced among with other basic virCommand* APIs by Dan in late 2010 (f16ad06fb2aeb5e5c9974). But this function was introduced by Dave in Jan 2010 so he couldn't have used it.
Also, why do I have this recollection related to portability of sscanf? I know we use it elsewhere, but some oddball issue that someone like Eric may recollect or know about.
I don't know about anything. But since we use it in our code pretty freely I assumed there is no problem with it.
diff --git a/src/util/viriscsi.c b/src/util/viriscsi.c index 2e55b3c10b..44788056fd 100644 --- a/src/util/viriscsi.c +++ b/src/util/viriscsi.c @@ -108,7 +108,6 @@ virISCSIGetSession(const char *devpath,
-#define LINE_SIZE 4096 #define IQN_FOUND 1 #define IQN_MISSING 0 #define IQN_ERROR -1 @@ -117,71 +116,56 @@ static int virStorageBackendIQNFound(const char *initiatoriqn, char **ifacename) { - int ret = IQN_ERROR, fd = -1; - char ebuf[64]; - FILE *fp = NULL; - char *line = NULL, *newline = NULL, *iqn = NULL, *token = NULL; + int ret = IQN_ERROR; + char *outbuf = NULL; + char *line = NULL; + char *iface = NULL; + char *iqn = NULL; virCommandPtr cmd = virCommandNewArgList(ISCSIADM, "--mode", "iface", NULL);
*ifacename = NULL;
- if (VIR_ALLOC_N(line, LINE_SIZE) != 0) { - virReportError(VIR_ERR_INTERNAL_ERROR, - _("Could not allocate memory for output of '%s'"), - ISCSIADM); + virCommandSetOutputBuffer(cmd, &outbuf); + if (virCommandRun(cmd, NULL) < 0) goto cleanup; - }
- memset(line, 0, LINE_SIZE); + /* Example of data we are dealing with: + * default tcp,<empty>,<empty>,<empty>,<empty> + * iser iser,<empty>,<empty>,<empty>,<empty> + * libvirt-iface-253db048 tcp,<empty>,<empty>,<empty>,iqn.2017-03.com.user:client + */
Nice to have an example especially since this is a bit of a edge case...
Another option - virStringSplitCount on the "\n" to get the number of lines and then on each line again using "," to tear apart the pieces. This I assume works as I don't have a initiatoriqn set up to test.
Any thoughts/recollections about sscanf? I assume it'll be felt that virStringSplit might be overkill,
Indeed.
but at least it's for other purposes and perhaps less susceptible to the line && *line adjustment.
I like sscanf() more because it's fewer lines of code, the variables I need are assigned value immediately and also memory footprint is smaller (I guess) since there's no need to store multiple arrays.
Understood - it's probably something really early on when I first started w/ libvirt and using sscanf was discouraged for something that has stuck in my head. Another part for me is readability - similar to the various [i]scsi code that uses regex's in order to parse output. That format is just a mish-mash of search patterns that causes my eyes to complain. Perhaps it's best to see this along with the combined 4&5 "again". Also add a non initiatoriqn to the mix (even the comment above) just so show the various formats. Hopefully using libiscsi makes all the personally displeasing regex and sscanf searching code disappear. John