Marcin 'Qrczak' Kowalczyk wrote:
File positions are not evil. They allow to treat files and devices in a uniform way.
Indeed, file positions are exactly as evil as indices into shared memory arrays, which is to say not evil at all. But suppose each shared memory array came with a shared "current index", and there was no way to create additional ones. Suppose you couldn't index the array by a local variable: instead, you had to store the local variable into the shared index register first, overwriting whatever was there before. If you only wanted to use the array as a source or sink for a single stream, that would be fine. In every other case, it would be awful. Even read-only sharing would require the invention of some sort of cooperative locking discipline, and if some process didn't respect the locking and couldn't be changed, read-only sharing would become impossible. That's just silly. The way to solve this problem is to decouple the index from the shared memory array. You can easily simulate the single-index behavior if that's what you want, but you also get a lot of additional functionality. -- Ben