1 files changed, 86 insertions, 0 deletions
diff --git a/bin/sum_bits.py b/bin/sum_bits.py
new file mode 100755
index 0000000..f211656
--- /dev/null
+++ b/bin/sum_bits.py
@@ -0,0 +1,86 @@
+#!/usr/bin/python
+#
+# Copyright 2014 Google Inc. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""
+Read the RAPPOR'd values on stdin, and sum the bits to produce a Counting Bloom
+filter by cohort.  This can then be analyzed by R.
+"""
+
+import csv
+import sys
+
+import rappor
+
+
+def SumBits(params, stdin, stdout):
+  csv_in = csv.reader(stdin)
+  csv_out = csv.writer(stdout)
+
+  num_cohorts = params.num_cohorts
+  num_bloombits = params.num_bloombits
+
+  sums = [[0] * num_bloombits for _ in xrange(num_cohorts)]
+  num_reports = [0] * num_cohorts
+
+  for i, row in enumerate(csv_in):
+    try:
+      (user_id, cohort, unused_bloom, unused_prr, irr) = row
+    except ValueError:
+      raise RuntimeError('Error parsing row %r' % row)
+
+    if i == 0:
+      continue  # skip header
+
+    cohort = int(cohort)
+    num_reports[cohort] += 1
+
+    if not len(irr) == params.num_bloombits:
+      raise RuntimeError(
+          "Expected %d bits, got %r" % (params.num_bloombits, len(irr)))
+    for i, c in enumerate(irr):
+      bit_num = num_bloombits - i - 1  # e.g. char 0 = bit 15, char 15 = bit 0
+      if c == '1':
+        sums[cohort][bit_num] += 1
+      else:
+        if c != '0':
+          raise RuntimeError('Invalid IRR -- digits should be 0 or 1')
+
+  for cohort in xrange(num_cohorts):
+    # First column is the total number of reports in the cohort.
+    row = [num_reports[cohort]] + sums[cohort]
+    csv_out.writerow(row)
+
+
+def main(argv):
+  try:
+    filename = argv[1]
+  except IndexError:
+    raise RuntimeError('Usage: sum_bits.py <params file>')
+  with open(filename) as f:
+    try:
+      params = rappor.Params.from_csv(f)
+    except rappor.Error as e:
+      raise RuntimeError(e)
+
+  SumBits(params, sys.stdin, sys.stdout)
+
+
+if __name__ == '__main__':
+  try:
+    main(sys.argv)
+  except RuntimeError, e:
+    print >>sys.stderr, e.args[0]
+    sys.exit(1)