This patch modifies `CipherOutputStream` to avoid pointless memory allocations when decrypting data using AEAD ciphers. This is related to #11597, which fixed a similar issue in `CipherInputStream`.
`Cipher.update` does not output any data when doing AEAD decryption; all data is buffered, and is later returned in one shot from `doFinal`. `Cipher.getOutputSize` returns the buffer size required by `doFinal`, which increases after every `update`, triggering new allocation in `ensureCapacity`. This patch addresses the issue by calling the `update` overload that returns the output buffer until one of the update calls returns some data. When that happens, we know that the cipher does not buffer everything until `doFinal`, and revert to original behavior. This PR adds a new benchmark for AES/GCM encryption and decryption using `CipherOutputStream`. Benchmark results before: Benchmark (dataSize) (keyLength) (provider) Mode Cnt Score Error Units AESGCMCipherOutputStream.decrypt 16384 128 thrpt 40 27949,624 ± 301,408 ops/s AESGCMCipherOutputStream.decrypt 1048576 128 thrpt 40 20,730 ± 0,875 ops/s AESGCMCipherOutputStream.encrypt 16384 128 thrpt 40 175358,641 ± 4235,808 ops/s AESGCMCipherOutputStream.encrypt 1048576 128 thrpt 40 2588,111 ± 35,469 ops/s after: Benchmark (dataSize) (keyLength) (provider) Mode Cnt Score Error Units AESGCMCipherOutputStream.decrypt 16384 128 thrpt 40 69644,217 ± 1081,032 ops/s AESGCMCipherOutputStream.decrypt 1048576 128 thrpt 40 949,667 ± 9,431 ops/s AESGCMCipherOutputStream.encrypt 16384 128 thrpt 40 173144,038 ± 3279,149 ops/s AESGCMCipherOutputStream.encrypt 1048576 128 thrpt 40 2514,840 ± 87,935 ops/s ------------- Commit messages: - Reduce allocation - CipherOutputStream benchmark Changes: https://git.openjdk.org/jdk/pull/11693/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11693&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8298865 Stats: 154 lines in 2 files changed: 150 ins; 0 del; 4 mod Patch: https://git.openjdk.org/jdk/pull/11693.diff Fetch: git fetch https://git.openjdk.org/jdk pull/11693/head:pull/11693 PR: https://git.openjdk.org/jdk/pull/11693
