google-cloud-storage: Failed to handle doubly-gzipped files

[shunping]

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Summary of the issue

When handling a doubly gzipped file (the first test file in the code below), the reader fails to reach the end of file.

API client name and version

google-cloud-storage 3.14.1

Reproduction steps: code

file: main.py

from google.cloud.storage import Blob
from google.cloud.storage import Bucket
from google.cloud.storage import Client

from google.cloud.storage.fileio import BlobReader

client = Client("apache-beam-testing")
bucket = Bucket(client=client, name="apache-beam-samples")

test_files = [
    "textio/textio-test-data.content-type-gzip-content-encoding-gzip.1k.txt.gz",
    "textio/textio-test-data.content-type-gzip-content-encoding-none.1k.txt.gz",
    "textio/textio-test-data.content-type-none-content-encoding-gzip.1k.txt.gz",
    "textio/textio-test-data.content-type-none-content-encoding-none.1k.txt.gz",
    "textio/textio-test-data.content-type-text-content-encoding-gzip.1k.txt.gz",
    "textio/textio-test-data.content-type-text-content-encoding-none.1k.txt.gz",
    "textio/textio-test-data.default.1k.txt",
    "textio/textio-test-data.default.1k.txt.gz",
    "textio/textio-test-data.gzip-local.1k.txt.gz",
]

for raw_download in [False, True]:
  print(f"-- raw_download={raw_download} --")
  for test_file in test_files:
    blob = Blob(test_file, bucket=bucket)
    reader = BlobReader(blob, raw_download=raw_download)
    a = reader.read(16777216)
    b = reader.read(16777216)
    print(f"[{test_file}] first_read:{len(a)}, second_read:{len(b)}")

Reproduction steps: supporting files

Run the code directly.

Reproduction steps: actual results

-- raw_download=False --
[textio/textio-test-data.content-type-gzip-content-encoding-gzip.1k.txt.gz] first_read:101000, second_read:101000   <--- problem
[textio/textio-test-data.content-type-gzip-content-encoding-none.1k.txt.gz] first_read:76478, second_read:0
[textio/textio-test-data.content-type-none-content-encoding-gzip.1k.txt.gz] first_read:101000, second_read:0
[textio/textio-test-data.content-type-none-content-encoding-none.1k.txt.gz] first_read:76478, second_read:0
[textio/textio-test-data.content-type-text-content-encoding-gzip.1k.txt.gz] first_read:101000, second_read:0
[textio/textio-test-data.content-type-text-content-encoding-none.1k.txt.gz] first_read:76478, second_read:0
[textio/textio-test-data.default.1k.txt] first_read:101000, second_read:0
[textio/textio-test-data.default.1k.txt.gz] first_read:76478, second_read:0
[textio/textio-test-data.gzip-local.1k.txt.gz] first_read:101000, second_read:0
-- raw_download=True --
[textio/textio-test-data.content-type-gzip-content-encoding-gzip.1k.txt.gz] first_read:76478, second_read:76478   <--- problem
[textio/textio-test-data.content-type-gzip-content-encoding-none.1k.txt.gz] first_read:76478, second_read:0
[textio/textio-test-data.content-type-none-content-encoding-gzip.1k.txt.gz] first_read:76478, second_read:0
[textio/textio-test-data.content-type-none-content-encoding-none.1k.txt.gz] first_read:76478, second_read:0
[textio/textio-test-data.content-type-text-content-encoding-gzip.1k.txt.gz] first_read:76478, second_read:0
[textio/textio-test-data.content-type-text-content-encoding-none.1k.txt.gz] first_read:76478, second_read:0
[textio/textio-test-data.default.1k.txt] first_read:101000, second_read:0
[textio/textio-test-data.default.1k.txt.gz] first_read:76478, second_read:0
[textio/textio-test-data.gzip-local.1k.txt.gz] first_read:76484, second_read:0

Reproduction steps: expected results

-- raw_download=False --
[textio/textio-test-data.content-type-gzip-content-encoding-gzip.1k.txt.gz] first_read:101000, second_read:0
[textio/textio-test-data.content-type-gzip-content-encoding-none.1k.txt.gz] first_read:76478, second_read:0
[textio/textio-test-data.content-type-none-content-encoding-gzip.1k.txt.gz] first_read:101000, second_read:0
[textio/textio-test-data.content-type-none-content-encoding-none.1k.txt.gz] first_read:76478, second_read:0
[textio/textio-test-data.content-type-text-content-encoding-gzip.1k.txt.gz] first_read:101000, second_read:0
[textio/textio-test-data.content-type-text-content-encoding-none.1k.txt.gz] first_read:76478, second_read:0
[textio/textio-test-data.default.1k.txt] first_read:101000, second_read:0
[textio/textio-test-data.default.1k.txt.gz] first_read:76478, second_read:0
[textio/textio-test-data.gzip-local.1k.txt.gz] first_read:101000, second_read:0
-- raw_download=True --
[textio/textio-test-data.content-type-gzip-content-encoding-gzip.1k.txt.gz] first_read:76478, second_read:0
[textio/textio-test-data.content-type-gzip-content-encoding-none.1k.txt.gz] first_read:76478, second_read:0
[textio/textio-test-data.content-type-none-content-encoding-gzip.1k.txt.gz] first_read:76478, second_read:0
[textio/textio-test-data.content-type-none-content-encoding-none.1k.txt.gz] first_read:76478, second_read:0
[textio/textio-test-data.content-type-text-content-encoding-gzip.1k.txt.gz] first_read:76478, second_read:0
[textio/textio-test-data.content-type-text-content-encoding-none.1k.txt.gz] first_read:76478, second_read:0
[textio/textio-test-data.default.1k.txt] first_read:101000, second_read:0
[textio/textio-test-data.default.1k.txt.gz] first_read:76478, second_read:0
[textio/textio-test-data.gzip-local.1k.txt.gz] first_read:76484, second_read:0

OS & version + platform

MacOS, Linux

Python environment

Python 3.12

Python dependencies

google-cloud-storage 3.14.1

Additional context

No response