[tip:perf/core] perf tools: Introduce pstack_peek()

[tip-bot for Namhyung Kim]

Commit-ID:  c8539e3fc630067020814657636b45095edfb5bb
Gitweb:     http://git.kernel.org/tip/c8539e3fc630067020814657636b45095edfb5bb
Author:     Namhyung Kim <namhyung@xxxxxxxxxx>
AuthorDate: Fri, 24 Apr 2015 10:15:32 +0900
Committer:  Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
CommitDate: Tue, 5 May 2015 18:13:22 -0300

perf tools: Introduce pstack_peek()

The pstack_peek() is to get the topmost entry without removing it.

Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: David Ahern <dsahern@xxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Link: http://lkml.kernel.org/r/1429838133-14001-1-git-send-email-namhyung@xxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
 tools/perf/util/pstack.c | 7 +++++++
 tools/perf/util/pstack.h | 1 +
 2 files changed, 8 insertions(+)

diff --git a/tools/perf/util/pstack.c b/tools/perf/util/pstack.c
index a126e6c..b234a6e 100644
--- a/tools/perf/util/pstack.c
+++ b/tools/perf/util/pstack.c
@@ -74,3 +74,10 @@ void *pstack__pop(struct pstack *pstack)
 	pstack->entries[pstack->top] = NULL;
 	return ret;
 }
+
+void *pstack__peek(struct pstack *pstack)
+{
+	if (pstack->top == 0)
+		return NULL;
+	return pstack->entries[pstack->top - 1];
+}
diff --git a/tools/perf/util/pstack.h b/tools/perf/util/pstack.h
index c3cb658..ded7f2e 100644
--- a/tools/perf/util/pstack.h
+++ b/tools/perf/util/pstack.h
@@ -10,5 +10,6 @@ bool pstack__empty(const struct pstack *pstack);
 void pstack__remove(struct pstack *pstack, void *key);
 void pstack__push(struct pstack *pstack, void *key);
 void *pstack__pop(struct pstack *pstack);
+void *pstack__peek(struct pstack *pstack);
 
 #endif /* _PERF_PSTACK_ */
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