RFR: 8246739: InputStream.skipNBytes could be implemented more efficiently [v4]

[Brian Burkhalter]

> Please review this modification of `java.io.InputStream.skipNBytes(long)` to improve its performance when `skip(long)` skips fewer than the requested number of bytes. In the current implementation, `skip(long)` is invoked once and, if not enough bytes have been skipped, then `read()` is invoked for each of the remaining bytes to be skipped. The proposed implementation instead repeatedly invokes `skip(long)` until the requested number of bytes has been skipped, or an error condition is encountered. For cases where `skip(long)` skips fewer bytes than the number requested, the new version was measured to be up to more than one thousand times faster than the old version. When `skip(long)` actually skips the requested number of bytes, the performance difference is insignificant.

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

  8246739: InputStream.skipNBytes could be implemented more efficiently

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/1329/files
  - new: https://git.openjdk.java.net/jdk/pull/1329/files/60fe0953..31678bfa

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=1329&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=1329&range=02-03

  Stats: 2 lines in 1 file changed: 1 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1329.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1329/head:pull/1329

PR: https://git.openjdk.java.net/jdk/pull/1329