Function inflateGetHeader 

#[unsafe(export_name = "inflateGetHeader")]
pub unsafe extern "C-unwind" fn inflateGetHeader(
    strm: *mut z_stream,
    head: *mut gz_header,
) -> i32

Requests that gzip header information be stored in the provided gz_header structure.

The inflateGetHeader function may be called after inflateInit2_ or inflateReset, and before the first call of inflate. As inflate processes the gzip stream, head.done is zero until the header is completed, at which time head.done is set to one. If a zlib stream is being decoded, then head.done is set to -1 to indicate that there will be no gzip header information forthcoming. Note that Z_BLOCK can be used to force inflate to return immediately after header processing is complete and before any actual data is decompressed.

• The text, time, xflags, and os fields are filled in with the gzip header contents.
• hcrc is set to true if there is a header CRC. (The header CRC was valid if done is set to one.)
• If extra is not NULL, then extra_max contains the maximum number of bytes to write to extra. Once done is true, extra_len contains the actual extra field length, and extra contains the extra field, or that field truncated if extra_max is less than extra_len.
• If name is not NULL, then up to name_max characters are written there, terminated with a zero unless the length is greater than name_max.
• If comment is not NULL, then up to comm_max characters are written there, terminated with a zero unless the length is greater than comm_max.

When any of extra, name, or comment are not NULL and the respective field is not present in the header, then that field is set to NULL to signal its absence. This allows the use of deflateSetHeader with the returned structure to duplicate the header. However if those fields are set to allocated memory, then the application will need to save those pointers elsewhere so that they can be eventually freed.

If inflateGetHeader is not used, then the header information is simply discarded. The header is always checked for validity, including the header CRC if present. inflateReset will reset the process to discard the header information. The application would need to call inflateGetHeader again to retrieve the header from the next gzip stream.

Returns

• Z_OK if success
• Z_STREAM_ERROR if the source stream state was inconsistent (such as zalloc being NULL)

Safety

• Either
  • strm is NULL
  • strm satisfies the requirements of &mut *strm and was initialized with inflateInit_ or similar
• Either
  • head is NULL
  • head satisfies the requirements of &mut *head
• If head is not NULL:
  • if head.extra is not NULL, it must be writable for at least head.extra_max bytes
  • if head.name is not NULL, it must be writable for at least head.name_max bytes
  • if head.comment is not NULL, it must be writable for at least head.comm_max bytes