Please consider this request to override the `java.io.InputStream` methods `readAllBytes()` and `readNBytes(int)` in `FileInputStream` with more performant implementations. The method overrides attempt to read all requested bytes into a single array of the required size rather than composing the result from a sequence of smaller arrays. An example of the performance improvements is as follows.
**readAllBytes** Before
Benchmark (length) Mode Cnt Score Error Units ReadAllBytes.readAllBytesFileInputStream 1000000 thrpt 20 2412.031 ± 7.309 ops/s ReadAllBytes.readAllBytesFileInputStream 10000000 thrpt 20 212.181 ± 0.369 ops/s ReadAllBytes.readAllBytesFileInputStream 100000000 thrpt 20 19.860 ± 0.048 ops/s ReadAllBytes.readAllBytesFileInputStream 1000000000 thrpt 20 1.298 ± 0.183 ops/s
After
Benchmark (length) Mode Cnt Score Error Units ReadAllBytes.readAllBytesFileInputStream 1000000 thrpt 20 8218.473 ± 43.425 ops/s ReadAllBytes.readAllBytesFileInputStream 10000000 thrpt 20 302.781 ± 1.273 ops/s ReadAllBytes.readAllBytesFileInputStream 100000000 thrpt 20 22.461 ± 0.084 ops/s ReadAllBytes.readAllBytesFileInputStream 1000000000 thrpt 20 1.502 ± 0.003 ops/s
**readNBytes**
`N = file_size / 2`
Before
Benchmark (length) Mode Cnt Score Error Units ReadAllBytes.readHalfBytesFileInputStream 1000000 thrpt 20 5585.500 ± 153.353 ops/s ReadAllBytes.readHalfBytesFileInputStream 10000000 thrpt 20 436.164 ± 1.104 ops/s ReadAllBytes.readHalfBytesFileInputStream 100000000 thrpt 20 40.167 ± 0.141 ops/s ReadAllBytes.readHalfBytesFileInputStream 1000000000 thrpt 20 3.291 ± 0.211 ops/s
After
Benchmark (length) Mode Cnt Score Error Units ReadAllBytes.readHalfBytesFileInputStream 1000000 thrpt 20 15463.210 ± 66.045 ops/s ReadAllBytes.readHalfBytesFileInputStream 10000000 thrpt 20 561.752 ± 0.951 ops/s ReadAllBytes.readHalfBytesFileInputStream 100000000 thrpt 20 45.043 ± 0.102 ops/s ReadAllBytes.readHalfBytesFileInputStream 1000000000 thrpt 20 4.629 ± 0.035 ops/s
Brian Burkhalter has updated the pull request incrementally with one additional commit since the last revision: 8264777: Handle readNBytes(0): src/test ------------- Changes: - all: https://git.openjdk.java.net/jdk/pull/3845/files - new: https://git.openjdk.java.net/jdk/pull/3845/files/5272d5ef..4fae0209 Webrevs: - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=3845&range=06 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=3845&range=05-06 Stats: 6 lines in 2 files changed: 5 ins; 0 del; 1 mod Patch: https://git.openjdk.java.net/jdk/pull/3845.diff Fetch: git fetch https://git.openjdk.java.net/jdk pull/3845/head:pull/3845 PR: https://git.openjdk.java.net/jdk/pull/3845