Add helpful error when trying to decompress gzip-wrapped data

[Lonami]

When trying to decompress the following data using this Rust code:

use miniz_oxide::inflate::decompress_to_vec;

fn main() {
    let data = [31, 139, 8, 0, 0, 0, 0, 0, 0, 3, 149, 147, 61, 75, 195, 80, 20, 134, 79, 62, 20, 84, 170, 1, 17, 28, 68, 28, 132, 110, 183, 247, 38, 185, 249, 154, 58, 10, 130, 116, 116, 170, 54, 109, 18, 11, 173, 169, 109, 90, 112, 210, 209, 81, 112, 112, 22, 127, 131, 56, 232, 232, 224, 143, 112, 112, 238, 159, 168, 55, 31, 234, 77, 91, 82, 26, 184, 57, 36, 79, 222, 115, 222, 251, 38, 9, 170, 27, 218, 209, 62, 128, 113, 76, 234, 181, 83, 82, 55, 31, 175, 223, 101, 0, 216, 249, 120, 217, 219, 102, 181, 244, 244, 186, 203, 10, 8, 108, 109, 18, 221, 70, 132, 234, 136, 152, 20, 81, 13, 222, 132, 148, 43, 11, 184, 144, 241, 178, 138, 49, 113, 176, 171, 90, 142, 175, 106, 45, 199, 79, 46, 217, 145, 63, 53, 126, 117, 241, 92, 49, 215, 215, 48, 17, 197, 185, 185, 179, 156, 252, 113, 49, 227, 91, 60, 39, 148, 240, 190, 196, 127, 95, 134, 217, 116, 176, 238, 89, 177, 47, 181, 200, 151, 180, 156, 206, 229, 247, 35, 229, 252, 176, 156, 8, 198, 252, 126, 138, 184, 144, 241, 57, 57, 106, 139, 114, 148, 167, 115, 178, 73, 46, 199, 34, 46, 100, 124, 206, 126, 245, 162, 185, 98, 166, 227, 242, 55, 16, 81, 49, 159, 227, 18, 125, 93, 222, 207, 202, 76, 14, 126, 172, 163, 69, 126, 148, 76, 87, 178, 9, 139, 213, 66, 148, 185, 177, 48, 0, 159, 211, 52, 167, 118, 198, 27, 189, 145, 134, 6, 145, 215, 65, 205, 176, 11, 240, 201, 158, 171, 150, 36, 104, 177, 90, 211, 37, 184, 99, 63, 11, 30, 2, 124, 63, 200, 73, 253, 98, 141, 206, 199, 233, 119, 18, 63, 11, 207, 34, 76, 38, 147, 155, 120, 193, 248, 48, 185, 23, 207, 186, 117, 214, 146, 26, 247, 57, 56, 1, 184, 63, 19, 18, 189, 82, 102, 51, 47, 162, 168, 55, 112, 42, 149, 8, 117, 189, 10, 123, 247, 65, 219, 95, 247, 195, 97, 127, 112, 53, 108, 244, 61, 144, 221, 246, 101, 192, 116, 171, 65, 24, 6, 29, 47, 13, 83, 73, 203, 15, 58, 186, 13, 141, 216, 3, 0, 0];
    assert!(decompress_to_vec(&data).is_ok());
}

I'm hitting the following error:

Err(TINFLStatus::Failed)

Python's gzip can decompress it just fine, though:

import gzip
data = [31, 139, 8, 0, 0, 0, 0, 0, 0, 3, 149, 147, 61, 75, 195, 80, 20, 134, 79, 62, 20, 84, 170, 1, 17, 28, 68, 28, 132, 110, 183, 247, 38, 185, 249, 154, 58, 10, 130, 116, 116, 170, 54, 109, 18, 11, 173, 169, 109, 90, 112, 210, 209, 81, 112, 112, 22, 127, 131, 56, 232, 232, 224, 143, 112, 112, 238, 159, 168, 55, 31, 234, 77, 91, 82, 26, 184, 57, 36, 79, 222, 115, 222, 251, 38, 9, 170, 27, 218, 209, 62, 128, 113, 76, 234, 181, 83, 82, 55, 31, 175, 223, 101, 0, 216, 249, 120, 217, 219, 102, 181, 244, 244, 186, 203, 10, 8, 108, 109, 18, 221, 70, 132, 234, 136, 152, 20, 81, 13, 222, 132, 148, 43, 11, 184, 144, 241, 178, 138, 49, 113, 176, 171, 90, 142, 175, 106, 45, 199, 79, 46, 217, 145, 63, 53, 126, 117, 241, 92, 49, 215, 215, 48, 17, 197, 185, 185, 179, 156, 252, 113, 49, 227, 91, 60, 39, 148, 240, 190, 196, 127, 95, 134, 217, 116, 176, 238, 89, 177, 47, 181, 200, 151, 180, 156, 206, 229, 247, 35, 229, 252, 176, 156, 8, 198, 252, 126, 138, 184, 144, 241, 57, 57, 106, 139, 114, 148, 167, 115, 178, 73, 46, 199, 34, 46, 100, 124, 206, 126, 245, 162, 185, 98, 166, 227, 242, 55, 16, 81, 49, 159, 227, 18, 125, 93, 222, 207, 202, 76, 14, 126, 172, 163, 69, 126, 148, 76, 87, 178, 9, 139, 213, 66, 148, 185, 177, 48, 0, 159, 211, 52, 167, 118, 198, 27, 189, 145, 134, 6, 145, 215, 65, 205, 176, 11, 240, 201, 158, 171, 150, 36, 104, 177, 90, 211, 37, 184, 99, 63, 11, 30, 2, 124, 63, 200, 73, 253, 98, 141, 206, 199, 233, 119, 18, 63, 11, 207, 34, 76, 38, 147, 155, 120, 193, 248, 48, 185, 23, 207, 186, 117, 214, 146, 26, 247, 57, 56, 1, 184, 63, 19, 18, 189, 82, 102, 51, 47, 162, 168, 55, 112, 42, 149, 8, 117, 189, 10, 123, 247, 65, 219, 95, 247, 195, 97, 127, 112, 53, 108, 244, 61, 144, 221, 246, 101, 192, 116, 171, 65, 24, 6, 29, 47, 13, 83, 73, 203, 15, 58, 186, 13, 141, 216, 3, 0, 0]
assert gzip.decompress(bytes(data)) is not None

I presume this is the same as sile/libflate#45, which I'm linking because it provides a clearer error message which may be helpful:

btype 0x11 of DEFLATE is reserved(error) value

I'm not sure if this bug should be filled here, but I guess it can't hurt. Is there any way to make this library decompress the data successfully, or a way to work around it?

I have also tested flate2 as mentioned in the README, and that's able to decompress the data too.

[oyvindln]

That data has a gzip wrapper around it. The core miniz_oxide doesn't support gzip directly, flate2 will deal with the wrapper if the correct decoder struct is used.

Adding support for that to miniz_oxide itself is not really something we've planned as it would pull in some extra dependencies. I would recommend just using flate2, though if you for whatever reason want to avoid that there is a gzip-header crate you can use to parse out the gzip wrapper manually before feeding the compressed data to miniz-oxide.

Could maybe make a clearer error type for this though, as the two first bytes of the gzip wrapper are unique.

[Lonami]

Oh, thank you for clarifying what's going on! It makes sense now. I'll let up to you whether to close this or leave it open to track improving the message.

[Plecra]

I don't think this is the responsibility of the library. Input data could be in any number of container formats, and I wouldn't expect the library to be able to identify whatever invalid data it was given

[Lonami]

Maybe it could be added to the documentation? "This error can occur due to various reasons, such as trying to decompress invalid data, data with a gzip header, etc."

[oyvindln]

Yeah sounds like a good idea.