问题
I'm reading gzip format specification, trying to understand byte-to-byte the following minimal example (generated using echo -n | gzip > /tmp/a.gz):
00000000 1f 8b 08 00 70 3c b4 5d 00 03 03 00 00 00 00 00 |....p<.]........|
00000010 00 00 00 00 |....|
00000014
I managed to map most of the bytes, but the "03 00" is something I cannot interpret. I wrote a Python script to fuzz different values for the "03" byte, but nothing other than that byte is allowed:
[15:13:05]>>> import subprocess
[15:13:08]>>> results = {}
[15:13:10]>>> for i in range(256): results[i] = subprocess.Popen(f'''echo '1f8b0800703cb45d0003{hex(i)[2:]:0>2}000000000000000000' | xxd -r -p | zcat''', shell=True, stderr=subprocess.PIPE).stderr.read()
...
Pp0�` ��@�X▒�x8�h(�H�[15:13:25]>>>
[15:13:26]>>> results2 = {value: list(k for k in results if results[k] == value) for value in results.values()}
[15:13:31]>>> results2
{b'\ngzip: stdin: invalid compressed data--format violated\n': [0, 1, 2, 6, 7, 8, 9, 10, 14, 15, 16, 17, 18, 22, 23, 24, 25, 26, 30, 31, 32, 33, 34, 38, 39, 40, 41, 42, 46, 47, 48, 49, 50, 54, 55, 56, 57, 58, 62, 63, 64, 65, 66, 70, 71, 72, 73, 74, 78, 79, 80, 81, 82, 86, 87, 88, 89, 90, 94, 95, 96, 97, 98, 102, 103, 104, 105, 106, 110, 111, 112, 113, 114, 118, 119, 120, 121, 122, 126, 127, 128, 129, 130, 134, 135, 136, 137, 138, 142, 143, 144, 145, 146, 150, 151, 152, 153, 154, 158, 159, 160, 161, 162, 166, 167, 168, 169, 170, 174, 175, 176, 177, 178, 182, 183, 184, 185, 186, 190, 191, 192, 193, 194, 198, 199, 200, 201, 202, 206, 207, 208, 209, 210, 214, 215, 216, 217, 218, 222, 223, 224, 225, 226, 230, 231, 232, 233, 234, 238, 239, 240, 241, 242, 244, 245, 246, 247, 248, 249, 250, 252, 253, 254, 255], b'': [3], b'\ngzip: stdin: unexpected end of file\n': [4, 5, 11, 12, 13, 19, 20, 21, 27, 28, 29, 35, 36, 37, 43, 44, 45, 51, 52, 53, 59, 60, 61, 67, 68, 69, 75, 76, 77, 83, 84, 85, 91, 92, 93, 99, 100, 101, 107, 108, 109, 115, 116, 117, 123, 124, 125, 131, 132, 133, 139, 140, 141, 147, 148, 149, 155, 156, 157, 163, 164, 165, 171, 172, 173, 179, 180, 181, 187, 188, 189, 195, 196, 197, 203, 204, 205, 211, 212, 213, 219, 220, 221, 227, 228, 229, 235, 236, 237, 243, 251]}
What's this 0x03 0x00 and where in the gzip (or DEFLATE) documentation can I find it?
来源：https://stackoverflow.com/questions/58571294/how-to-interpret-the-final-0x03-0x00-in-this-minimal-gzip-sample