forked from mirrors/gecko-dev
5b24f801f7
This is needed for bug 1500926. It takes the approach of taking a JSFlatString and using AutoAssertCannotGC to read the memory directly from the JS heap. This lets us avoid re-encoding strings when performing lookups, which can be advantageous. Only ASCII strings are supported by this handler, and wide strings are hashed as though they contain only values under 0x7f. This is OK as invalid keys to perfecthash may return any hashtable entry. Differential Revision: https://phabricator.services.mozilla.com/D9405
67 lines
1.8 KiB
Python
67 lines
1.8 KiB
Python
# This Source Code Form is subject to the terms of the Mozilla Public
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# License, v. 2.0. If a copy of the MPL was not distributed with this
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# file, You can obtain one at http://mozilla.org/MPL/2.0/.
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from __future__ import print_function
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from mozparsers.shared_telemetry_utils import ParserError
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from perfecthash import PerfectHash
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PHFSIZE = 512
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from mozparsers import parse_histograms
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import sys
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import buildconfig
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banner = """/* This file is auto-generated, see gen_histogram_phf.py. */
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"""
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header = """
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#ifndef mozilla_TelemetryHistogramNameMap_h
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#define mozilla_TelemetryHistogramNameMap_h
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#include "mozilla/PerfectHash.h"
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namespace mozilla {
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namespace Telemetry {
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"""
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footer = """
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} // namespace mozilla
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} // namespace Telemetry
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#endif // mozilla_TelemetryHistogramNameMap_h
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"""
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def main(output, *filenames):
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"""
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Generate a Perfect Hash Table for the Histogram name -> Histogram ID lookup.
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The table is immutable once generated and we can avoid any dynamic memory allocation.
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"""
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output.write(banner)
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output.write(header)
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try:
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histograms = list(parse_histograms.from_files(filenames))
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histograms = [h for h in histograms if h.record_on_os(buildconfig.substs["OS_TARGET"])]
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except ParserError as ex:
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print("\nError processing histograms:\n" + str(ex) + "\n")
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sys.exit(1)
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histograms = [(bytearray(hist.name(), 'ascii'), idx) for (idx, hist) in enumerate(histograms)]
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name_phf = PerfectHash(histograms, PHFSIZE)
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output.write(name_phf.cxx_codegen(
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name='HistogramIDByNameLookup',
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entry_type="uint32_t",
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lower_entry=lambda (_, v): str(v),
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key_type="const nsACString&",
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key_bytes="aKey.BeginReading()",
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key_length="aKey.Length()"))
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output.write(footer)
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if __name__ == '__main__':
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main(sys.stdout, *sys.argv[1:])
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