ipa: libipa: Allow creation of empty Histogram

For convenience's sake allow the creation of empty Histograms so
they can be embedded within other Classes and filled out with
data at some later point in time.

Reviewed-by: Stefan Klug <stefan.klug@ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
Signed-off-by: Daniel Scally <dan.scally@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

2 files changed, 10 insertions, 0 deletions

diff --git a/src/ipa/libipa/histogram.cpp b/src/ipa/libipa/histogram.cpp
index 6b5cde8e..c1aac59b 100644
--- a/src/ipa/libipa/histogram.cpp
+++ b/src/ipa/libipa/histogram.cpp
@@ -29,6 +29,15 @@ namespace ipa {
  */
 
 /**
+ * \fn Histogram::Histogram()
+ * \brief Construct an empty Histogram
+ *
+ * This empty constructor exists largely to allow Histograms to be embedded in
+ * other classes which may be created before the contents of the Histogram are
+ * known.
+ */
+
+/**
  * \brief Create a cumulative histogram
  * \param[in] data A pre-sorted histogram to be passed
  */
diff --git a/src/ipa/libipa/histogram.h b/src/ipa/libipa/histogram.h
index 05bb4b80..54bb2a19 100644
--- a/src/ipa/libipa/histogram.h
+++ b/src/ipa/libipa/histogram.h
@@ -22,6 +22,7 @@ namespace ipa {
 class Histogram
 {
 public:
+	Histogram() { cumulative_.push_back(0); }
 	Histogram(Span<const uint32_t> data);
 	size_t bins() const { return cumulative_.size() - 1; }
 	uint64_t total() const { return cumulative_[cumulative_.size() - 1]; }