| # Copyright 2013 The Chromium Authors. All rights reserved. |
| # Use of this source code is governed by a BSD-style license that can be |
| # found in the LICENSE file. |
| import json |
| import logging |
| |
| def SubtractHistogram(histogram_json, start_histogram_json): |
| """Subtracts a previous histogram from a histogram. Both parameters are json |
| serializations of histograms.""" |
| start_histogram = json.loads(start_histogram_json) |
| # It's ok if the start histogram is empty (we had no data, maybe even no |
| # histogram at all, at the start of the test). |
| if 'buckets' not in start_histogram: |
| return histogram_json |
| |
| histogram = json.loads(histogram_json) |
| if ('pid' in start_histogram and 'pid' in histogram |
| and start_histogram['pid'] != histogram['pid']): |
| raise Exception( |
| 'Trying to compare histograms from different processes (%d and %d)' |
| % (start_histogram['pid'], histogram['pid'])) |
| |
| start_histogram_buckets = dict() |
| for b in start_histogram['buckets']: |
| start_histogram_buckets[b['low']] = b['count'] |
| |
| new_buckets = [] |
| for b in histogram['buckets']: |
| new_bucket = b |
| low = b['low'] |
| if low in start_histogram_buckets: |
| new_bucket['count'] = b['count'] - start_histogram_buckets[low] |
| if new_bucket['count'] < 0: |
| logging.error('Histogram subtraction error, starting histogram most ' |
| 'probably invalid.') |
| if new_bucket['count']: |
| new_buckets.append(new_bucket) |
| histogram['buckets'] = new_buckets |
| histogram['count'] -= start_histogram['count'] |
| |
| return json.dumps(histogram) |
| |
| def GetHistogramFromDomAutomation(function, name, tab): |
| # TODO(jeremy): Remove references to |
| # domAutomationController when we update the reference builds. |
| js = ('(window.statsCollectionController ? ' |
| 'statsCollectionController : ' |
| 'domAutomationController).%s("%s")' % |
| (function, name)) |
| return tab.EvaluateJavaScript(js) |
