[libvirt] [PATCH v2 04/20] virlog: Introduce virLogFindOutput

[Erik Skultety]

Outputs are a bit trickier than filters, because if the user(config)-specified
set of outputs does contain duplicates. So, not only we would log twice, but
we would also leek FD for journald, since that one is global and is overwritten
every time a journald output was specified. For compatibility reasons, we
cannot just error out and forbid the daemon to start if we find duplicate
outputs which do not make sense. Instead, we could silently take into account
only the last occurrence of the duplicate output and remove all the previous
ones, so that the logger will not try to use them when it is looping over all
of its registered outputs.

Signed-off-by: Erik Skultety <eskultet at redhat.com>
---
 src/libvirt_private.syms |  1 +
 src/util/virlog.c        | 32 ++++++++++++++++++++++++++++++++
 src/util/virlog.h        |  2 ++
 3 files changed, 35 insertions(+)

diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index 088f9f3..d28405c 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -1847,6 +1847,7 @@ virLogDefineOutput;
 virLogFilterFree;
 virLogFilterListFree;
 virLogFilterNew;
+virLogFindOutput;
 virLogGetDefaultPriority;
 virLogGetFilters;
 virLogGetNbFilters;
diff --git a/src/util/virlog.c b/src/util/virlog.c
index e4dc84b..5916ac8 100644
--- a/src/util/virlog.c
+++ b/src/util/virlog.c
@@ -1650,3 +1650,35 @@ virLogFilterNew(const char *match,
 
     return ret;
 }
+
+
+/**
+ * virLogFindOutput:
+ * @outputs: a list of outputs where to look for the output of type @dest
+ * @noutputs: number of elements in @outputs
+ * @dest: destination type of an output
+ * @opaque: opaque data to the method (only filename at the moment)
+ *
+ * Looks for an output of destination type @dest in the source list @outputs.
+ * If such an output exists, index of the object in the list is returned.
+ * In case of the destination being of type FILE also a comparison of the
+ * output's filename with @opaque is performed first.
+ *
+ * Returns the index of the object in the list or -1 if no object matching the
+ * specified @dest type and/or @opaque data one was found.
+ */
+int
+virLogFindOutput(virLogOutputPtr *outputs, size_t noutputs,
+                 virLogDestination dest, const void *opaque)
+{
+    size_t i;
+    const char *name = opaque;
+
+    for (i = 0; i < noutputs; i++) {
+        if (dest == outputs[i]->dest &&
+            (dest != VIR_LOG_TO_FILE || STREQ(outputs[i]->name, name)))
+                return i;
+    }
+
+    return -1;
+}
diff --git a/src/util/virlog.h b/src/util/virlog.h
index a56d297..2045c06 100644
--- a/src/util/virlog.h
+++ b/src/util/virlog.h
@@ -235,5 +235,7 @@ virLogOutputPtr virLogOutputNew(virLogOutputFunc f,
 virLogFilterPtr virLogFilterNew(const char *match,
                                 virLogPriority priority,
                                 unsigned int flags);
+int virLogFindOutput(virLogOutputPtr *outputs, size_t noutputs,
+                     virLogDestination dest, const void *opaque);
 
 #endif
-- 
2.5.5