Panic when reading from a Sampling port destination

[dadada]

I have a partition that runs a process that very frequently reads from a sampling port. After running the partition for some time, I reliably get a read from an empty file, which causes a panic. The panic is fixed in #15, but the error persists. This is from the execution of the partition (Echo) with the fix from #15 applied. Now it panics in apex-rs?

 ERROR Partition: Echo                              > PanicInfo {
 ERROR Partition: Echo                              >     payload: Any { .. },
 ERROR Partition: Echo                              >     message: Some(
 ERROR Partition: Echo                              >         called `Result::unwrap()` on an `Err` value: TypedError { err: Panic, source: failed to fill whole buffer
 ERROR Partition: Echo                              >
 ERROR Partition: Echo                              >         Stack backtrace:
 ERROR Partition: Echo                              >            0: anyhow::error::<impl core::convert::From<E> for anyhow::Error>::from
 ERROR Partition: Echo                              >            1: linux_apex_core::file::TempFile<T>::read
 ERROR Partition: Echo                              >            2: <S as apex_rs::apex::sampling::abstraction::ApexSamplingPortP4Ext>::sampling_port_receive_unchecked
 ERROR Partition: Echo                              >            3: <apex_rs::apex::sampling::abstraction::SamplingPortDestination<_,H> as echo::echo::RunableProcess>::run_process
 ERROR Partition: Echo                              >            4: echo::entry_point_aperiodic
 ERROR Partition: Echo                              >            5: apex_rs_linux::process::Process::start::{{closure}} },
 ERROR Partition: Echo                              >     ),
 ERROR Partition: Echo                              >     location: Location {
 ERROR Partition: Echo                              >         file: "/home/dadada/.cargo/git/checkouts/apex-linux-53d7a06a5cb9e565/cdc4225/partition/src/apex.rs",
 ERROR Partition: Echo                              >         line: 157,
 ERROR Partition: Echo                              >         col: 14,
 ERROR Partition: Echo                              >     },
 ERROR Partition: Echo                              >     can_unwind: true,
 ERROR Partition: Echo                              > }

[dadada]

I've updated the fix in #15 so it does not panic somewhere else. Unless the partition unwraps the result, there should be no panic now. But the fact that the file backing the sampling port can be empty still worries me.

[dadada]

Original panic info

 ERROR Partition: Echo                              > PanicInfo {
 ERROR Partition: Echo                              >     payload: Any { .. },
 ERROR Partition: Echo                              >     message: Some(
 ERROR Partition: Echo                              >         index out of bounds: the len is 0 but the index is 0,
 ERROR Partition: Echo                              >     ),
 ERROR Partition: Echo                              >     location: Location {
 ERROR Partition: Echo                              >         file: "/home/dadada/.cargo/git/checkouts/apex-linux-1bbea6f3d09316d7/2f69d2b/core/src/file.rs",
 ERROR Partition: Echo                              >         line: 96,
 ERROR Partition: Echo                              >         col: 21,
 ERROR Partition: Echo                              >     },
 ERROR Partition: Echo                              >     can_unwind: true,
 ERROR Partition: Echo 

[dadada]

This might not be a read from an empty file, but a read from the end of the file. The cursor may be moved between the seek to 0 and the read.