add benchmark and todo to readme

Author: CAFxX

README.md

@@ -28,3 +28,71 @@ Note that it is allowed to pass to the `PutXxx` functions objects that have been
 rp := httputil.NewSingleHostReverseProxy(target)
 rp.BufferPool = bytespool.GetBufferPool(32*1024)
 ```
+
+## Benchmarks
+
+There is a small set of benchmarks you can run with `make bench` (you need to have [`benchstat`](https://golang.org/x/perf/cmd/benchstat) on your `PATH`), from which you can validate that in steady state no allocations are performed even for `[]byte`:
+
+```
+name                           time/op
+GetBytesSlice-12               8.56ns ±14%
+GetBytesSliceSemiStatic-12     8.26ns ±14%
+GetBytesSliceStatic-12         8.19ns ±16%
+GetBytesSlicePtr-12            5.18ns ±23%
+GetBytesSlicePtrSemiStatic-12  4.74ns ±22%
+GetBytesSlicePtrStatic-12      4.74ns ±22%
+GetBytesBuffer-12              3.64ns ± 8%
+GetBytesBufferSemiStatic-12    3.18ns ± 5%
+GetBytesBufferStatic-12        3.12ns ± 5%
+GetBufioReader-12              5.82ns ± 7%
+GetBufioReaderSemiStatic-12    5.45ns ±10%
+GetBufioReaderStatic-12        5.39ns ± 6%
+GetBufioWriter-12              4.02ns ± 2%
+GetBufioWriterSemiStatic-12    3.73ns ± 4%
+GetBufioWriterStatic-12        3.56ns ± 3%
+
+name                           alloc/op
+GetBytesSlice-12                0.00B
+GetBytesSliceSemiStatic-12      0.00B
+GetBytesSliceStatic-12          0.00B
+GetBytesSlicePtr-12             0.00B
+GetBytesSlicePtrSemiStatic-12   0.00B
+GetBytesSlicePtrStatic-12       0.00B
+GetBytesBuffer-12               0.00B
+GetBytesBufferSemiStatic-12     0.00B
+GetBytesBufferStatic-12         0.00B
+GetBufioReader-12               0.00B
+GetBufioReaderSemiStatic-12     0.00B
+GetBufioReaderStatic-12         0.00B
+GetBufioWriter-12               0.00B
+GetBufioWriterSemiStatic-12     0.00B
+GetBufioWriterStatic-12         0.00B
+
+name                           allocs/op
+GetBytesSlice-12                 0.00
+GetBytesSliceSemiStatic-12       0.00
+GetBytesSliceStatic-12           0.00
+GetBytesSlicePtr-12              0.00
+GetBytesSlicePtrSemiStatic-12    0.00
+GetBytesSlicePtrStatic-12        0.00
+GetBytesBuffer-12                0.00
+GetBytesBufferSemiStatic-12      0.00
+GetBytesBufferStatic-12          0.00
+GetBufioReader-12                0.00
+GetBufioReaderSemiStatic-12      0.00
+GetBufioReaderStatic-12          0.00
+GetBufioWriter-12                0.00
+GetBufioWriterSemiStatic-12      0.00
+GetBufioWriterStatic-12          0.00
+```
+
+## Developing
+
+Most of the code is in `gen/main.go`. You can run `make generate` to generate `bytespool.go`.
+
+## TODO
+
+- Split low-level APIs in a separate package
+- Ensure that users of the low-level API are not forced to compile also the high-level APIs
+- Define BufferPool-like interfaces for all objects (e.g. BytesBufferPool)
+- Provide non-singleton pools