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| author | isherman@chromium.org <isherman@chromium.org@0039d316-1c4b-4281-b951-d872f2087c98> | 2011-10-14 01:48:32 +0000 |
|---|---|---|
| committer | isherman@chromium.org <isherman@chromium.org@0039d316-1c4b-4281-b951-d872f2087c98> | 2011-10-14 01:48:32 +0000 |
| commit | c340bf4185b0cfba66eae8299fce69741553e335 (patch) | |
| tree | 60d445a43c07865eafa18f219e078231a11576e8 /base/metrics/histogram.h | |
| parent | 27315ce408fc3e67c5195704ecb61b5462ce01fc (diff) | |
| download | chromium_src-c340bf4185b0cfba66eae8299fce69741553e335.zip chromium_src-c340bf4185b0cfba66eae8299fce69741553e335.tar.gz chromium_src-c340bf4185b0cfba66eae8299fce69741553e335.tar.bz2 | |
Expand the inline documentation for the HISTOGRAM_ENUMERATION macros.
This should help to reduce confusion about the recommended upper- and lower-bounds for enumerated histograms.
BUG=none
TEST=none
Review URL: http://codereview.chromium.org/8273022
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@105440 0039d316-1c4b-4281-b951-d872f2087c98
Diffstat (limited to 'base/metrics/histogram.h')
| -rw-r--r-- | base/metrics/histogram.h | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/base/metrics/histogram.h b/base/metrics/histogram.h index 7a73f96..401ece7 100644 --- a/base/metrics/histogram.h +++ b/base/metrics/histogram.h @@ -163,7 +163,11 @@ class Lock; base::Histogram::kNoFlags)) // Support histograming of an enumerated value. The samples should always be -// less than boundary_value. +// strictly less than |boundary_value| -- this prevents you from running into +// problems down the line if you add additional buckets to the histogram. Note +// also that, despite explicitly setting the minimum bucket value to |1| below, +// it is fine for enumerated histograms to be 0-indexed -- this is because +// enumerated histograms should never have underflow. #define HISTOGRAM_ENUMERATION(name, sample, boundary_value) \ STATIC_HISTOGRAM_POINTER_BLOCK(name, Add(sample), \ base::LinearHistogram::FactoryGet(name, 1, boundary_value, \ @@ -266,6 +270,8 @@ class Lock; base::BooleanHistogram::FactoryGet(name, \ base::Histogram::kUmaTargetedHistogramFlag)) +// The samples should always be strictly less than |boundary_value|. For more +// details, see the comment for the |HISTOGRAM_ENUMERATION| macro, above. #define UMA_HISTOGRAM_ENUMERATION(name, sample, boundary_value) \ STATIC_HISTOGRAM_POINTER_BLOCK(name, Add(sample), \ base::LinearHistogram::FactoryGet(name, 1, boundary_value, \ |