# Rewrite metadata on the fly using a list of (target,rule).
# @category Source / Track Processing
# @param l List of (target,value) rewriting rules
# @param ~insert_missing \
# Treat track beginnings without metadata \
# as having empty ones.
def rewrite_metadata(l,~insert_missing=true,s)
def map(m)
def apply(x)
label = fst(x)
meta = snd(x)
if list.mem_assoc(label,l) then
pattern = l[label]
(label,pattern % m)
else
(label,meta)
end
end
m = list.map(apply,m)
def add(m,x)
label = fst(x)
pattern = snd(x)
# If m does not have (label,_), then it was
# not processed previously, we have to
# add it now..
if not list.mem_assoc(label,m) then
list.append(m,[(label,pattern % m)])
else
m
end
end
list.fold(add,m,l)
end
map_metadata(map,insert_missing=insert_missing,s)
end
