Fixed memory leak in readAllFromFileHandle due to use of for/yield #992
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mpilquist
commented
Nov 23, 2017
| @@ -111,9 +111,10 @@ private[file] object FileHandle { | |||
| asyncCompletionHandler[F, Lock](f => chan.lock(position, size, shared, null, f)) | |||
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| override def read(numBytes: Int, offset: Long): F[Option[Chunk[Byte]]] = { | |||
| val buf = ByteBuffer.allocate(numBytes) | |||
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Wrapped these buffer allocations in F.delay so the returned action is safe to use more than once. Unrelated to memory leak.
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wow nice catch |
mpilquist
commented
Nov 23, 2017
| private def _readAllFromFileHandle0[F[_]](chunkSize: Int, offset: Long)(h: FileHandle[F]): Pull[F, Byte, Unit] = for { | ||
| res <- Pull.eval(h.read(chunkSize, offset)) | ||
| next <- res.fold[Pull[F, Byte, Unit]](Pull.done)(o => Pull.output(o) *> _readAllFromFileHandle0(chunkSize, offset + o.size)(h)) | ||
| } yield next |
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This yield next was the cause of the leak -- each time through this pull, we'd push a map(identity) in to the FreeC, which would accumulate on the return. In essence, the yield results in the recursive call being out of tail position.
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Thanks for the explanation. It took me a while to realise what was going on here and I would have really struggled to find this.
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Fixes #987.