tools/get_perfetto_prebuilt.py

# Copyright (C) 2021 The Android Open Source Project
#
# 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.
"""
This source defines a self-contained function to fetch a perfetto prebuilt.

This function is copy/pasted by //tools/roll-prebuilts in different places:
- Into the //tools/{trace_processor, traceconv} scripts, which are just plain
  wrappers around executables.
- Into the //tools/{heap_profiler, record_android_trace} scripts, which contain
  some other hand-written python code.
In both cases toll-prebuilts copies this source (together with a manifest) into
a section annotated with "BEGIN_SECTION_GENERATED_BY(roll-prebuilts)" / END... .
The automated-copy-paste is to keep those script hermetic, so people can just
download and run them without checking out the repo.

The manifest argument looks as follows in the generated files:
PERFETTO_PREBUILT_MANIFEST = [{
    'tool': 'trace_to_text',
    'arch': 'mac-amd64',
    'file_name': 'trace_to_text',
    'file_size': 7087080,
    'url': https://commondatastorage.googleapis.com/.../trace_to_text',
    'sha256': 7d957c005b0dc130f5bd855d6cec27e060d38841b320d04840afc569f9087490',
    'platform': 'darwin',
    'machine': 'x86_64'
  },
  ...
]

The intended usage is:

bin_path = get_perfetto_prebuilt('trace_processor_shell')
subprocess.call(bin_path, ...)
"""

from logging import exception

PERFETTO_PREBUILT_MANIFEST = []

# COPIED_SECTION_START_MARKER


# DO NOT EDIT. If you wish to make edits to this code, you need to change only
# //tools/get_perfetto_prebuilt.py and run /tools/roll-prebuilts to regenerate
# all the others scripts this is embedded into.
def get_perfetto_prebuilt(tool_name, soft_fail=False, arch=None):
  """ Downloads the prebuilt, if necessary, and returns its path on disk. """

  # The first time this is invoked, it downloads the |url| and caches it into
  # ~/.perfetto/prebuilts/$tool_name. On subsequent invocations it just runs the
  # cached version.
  def download_or_get_cached(file_name, url, sha256):
    import os, hashlib, subprocess
    dir = os.path.join(
        os.path.expanduser('~'), '.local', 'share', 'perfetto', 'prebuilts')
    os.makedirs(dir, exist_ok=True)
    bin_path = os.path.join(dir, file_name)
    sha256_path = os.path.join(dir, file_name + '.sha256')
    needs_download = True

    # Avoid recomputing the SHA-256 on each invocation. The SHA-256 of the last
    # download is cached into file_name.sha256, just check if that matches.
    if os.path.exists(bin_path) and os.path.exists(sha256_path):
      with open(sha256_path, 'rb') as f:
        digest = f.read().decode()
        if digest == sha256:
          needs_download = False

    if needs_download:
      # Either the filed doesn't exist or the SHA256 doesn't match.
      tmp_path = bin_path + '.tmp'
      print('Downloading ' + url)
      subprocess.check_call(['curl', '-f', '-L', '-#', '-o', tmp_path, url])
      with open(tmp_path, 'rb') as fd:
        actual_sha256 = hashlib.sha256(fd.read()).hexdigest()
      if actual_sha256 != sha256:
        raise Exception('Checksum mismatch for %s (actual: %s, expected: %s)' %
                        (url, actual_sha256, sha256))
      os.chmod(tmp_path, 0o755)
      os.rename(tmp_path, bin_path)
      with open(sha256_path, 'w') as f:
        f.write(sha256)
    return bin_path
    # --- end of download_or_get_cached() ---

  # --- get_perfetto_prebuilt() function starts here. ---
  import os, platform, sys
  plat = sys.platform.lower()
  machine = platform.machine().lower()
  manifest_entry = None
  for entry in PERFETTO_PREBUILT_MANIFEST:
    # If the caller overrides the arch, just match that (for Android prebuilts).
    if arch and entry.get('arch') == arch:
      manifest_entry = entry
      break
    # Otherwise guess the local machine arch.
    if entry.get('tool') == tool_name and entry.get(
        'platform') == plat and machine in entry.get('machine', []):
      manifest_entry = entry
      break
  if manifest_entry is None:
    if soft_fail:
      return None
    raise Exception(
        ('No prebuilts available for %s-%s\n' % (plat, machine)) +
        'See https://perfetto.dev/docs/contributing/build-instructions')

  return download_or_get_cached(
      file_name=manifest_entry['file_name'],
      url=manifest_entry['url'],
      sha256=manifest_entry['sha256'])