import timeit
import statistics

WITH_FNAME = """
from gzip import GzipFile, decompress, _read_gzip_header
import io
fileobj = io.BytesIO()
g = GzipFile(fileobj=fileobj, mode='wb', filename='compressable_file')
g.write(b'')
g.close()
data=fileobj.getvalue()
"""
WITH_NO_FLAGS = """
import io
from gzip import compress, _read_gzip_header
data = gzip.compress(b'', mtime=0)
"""
ALLFLAGHEADER = (
    b'\x1f\x8b\x08\x1f\x00\x00\x00\x00\x00\xff'
    b'\x05\x00'  # Xlen = 5
    b'extra'
    b'name\x00'
    b'comment\x00')
WITH_ALL_FLAGS = f"""
import zlib
from gzip import _read_gzip_header
import io

header = {ALLFLAGHEADER}
hcrc = zlib.crc32(header) & 0xffff
compressed = zlib.compress(b"", wbits=-15)
trailer = bytes(8)  # No length, and checksum is zero as well
data = header + hcrc.to_bytes(2, "little") + compressed + trailer
"""

def benchmark(name, setup, loops=5000, runs=100):
    print(f"{name}")
    results = [timeit.timeit("_read_gzip_header(io.BytesIO(data))", setup, number=loops) for _ in range(runs)]
    # Calculate microseconds
    results = [(result / loops) * 1_000_000 for result in results]
    print(f"average: {round(statistics.mean(results), 2)}, "
          f"range: {round(min(results), 2)}-{round(max(results),2)} "
          f"stdev: {round(statistics.stdev(results),2)}")


if __name__ == "__main__":
    benchmark("with_fname", WITH_FNAME)
    benchmark("with_noflags", WITH_FNAME)
    benchmark("All flags (incl FHCRC)", WITH_ALL_FLAGS)