RFR: 8140241: (fc) Data transfer from FileChannel to itself causes hang in case of overlap [v5]

[Brian Burkhalter]

> This request proposes to fix a failure on macOS which occurs when transferring to or from a file channel from or to the same file channel when the source and destination intervals overlap.

Brian Burkhalter has updated the pull request incrementally with one additional commit since the last revision:

  8140241: Use pattern matching; remove sync on position lock

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/5061/files
  - new: https://git.openjdk.java.net/jdk/pull/5061/files/35386c14..bf431122

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=5061&range=04
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=5061&range=03-04

  Stats: 9 lines in 1 file changed: 0 ins; 2 del; 7 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5061.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5061/head:pull/5061

PR: https://git.openjdk.java.net/jdk/pull/5061