annotate docs/spec/fv0.tikz @ 580:633614461994

API for retrieving a track's data.

A new function, audiodb_retrieve_datum() fills a provided adb_datum_t
structure with the data corresponding to a given database key; the
companion audiodb_free_datum() function frees the data in a given datum
appropriately.

Just in case, I continue to require passing in the adb_t * as the first
argument to audiodb_free_datum(), even though it's not currently used:
I couldn't convince myself that _all_ possible implementations could
free a datum without reference to the adb_t.

This meant rewriting the internal code to use a new internal
audiodb_really_free_datum() function, which audiodb_free_datum() also
calls.

Sanity-checked by implementing a binding in sb-alien to this function,
lightly-tested.

All this fixes ticket:20 in Trac.

\foreach \y/\col in {0/53,0.2/32,0.4/37,0.6/4,0.8/63} {
  \fill[black!\col!white] ($(-0.1,0)+(0,\y)$) rectangle ($(0.1,0.2)+(0,\y)$);
}