Slices and GC

[BLM]

Recently I've been working on some projects that involve parsing 
binary files. I've mainly been using std.file.read() to get the 
whole file as a huge array and then extracting slices. I had 
initially assumed that the GC would free any chunks of the array 
that didn't end up being referenced by these slices, but after 
reading some more, it looks like the whole array is kept in 
memory even if only a few elements are actually referenced. Is 
this actually the case? If so, might the language be extended to 
handle this situation?