Open an existing file descriptor for reading or writing.
@param fd file descriptor
Note that the file must be opened in binary mode, or else
there will be problems on platforms that make a difference
between text and binary mode.
@param mode mode matching /rwag[u0-9]+/: 'r' for reading, 'w' for
writing, 'a' for appending, 'g' for gzip rather than BGZF
compression (with 'w' only), and digit specifies the zlib
compression level.
Note that there is a distinction between 'u' and '0': the
first yields plain uncompressed output whereas the latter
outputs uncompressed data wrapped in the zlib format.
@return BGZF file handler; 0 on error
Open an existing file descriptor for reading or writing.
@param fd file descriptor Note that the file must be opened in binary mode, or else there will be problems on platforms that make a difference between text and binary mode. @param mode mode matching /rwag[u0-9]+/: 'r' for reading, 'w' for writing, 'a' for appending, 'g' for gzip rather than BGZF compression (with 'w' only), and digit specifies the zlib compression level. Note that there is a distinction between 'u' and '0': the first yields plain uncompressed output whereas the latter outputs uncompressed data wrapped in the zlib format. @return BGZF file handler; 0 on error