Converting a Go string to a string suitable use a specialized function,
UTF16Encode, that can encode the string directly to a malloc'ed buffer. That
way, only two copies are made when strings are passed from Go to Java; once
for UTF-8 to UTF-16 encoding and once for the creation of the Java String.
This CL implements the same optimization in the other direction, with a
UTF-16 to UTF-8 decoder implemented in C. Unfortunately, while calling into a
Go decoder also saves the extra copy, the Cgo overhead makes the calls much
slower for short strings.
To alleviate the risk of introducing decoding bugs, I've added the tests from
the encoding/utf16 package to SeqTest.
As a sideeffect, both Java and ObjC now always copy strings, regardless of
the argument mode. The cpy argument can therefore be removed from the string
conversion functions. Furthermore, the modeRetained and modeReturned modes
can be collapsed into just one.
While we're here, delete a leftover function from seq/strings.go that
wasn't removed when the old seq buffers went away.
Benchmarks, as compared with benchstat over 5 runs:
name old time/op new time/op delta
JavaStringShort 11.4µs ±13% 11.6µs ± 4% ~ (p=0.859 n=10+5)
JavaStringShortDirect 19.5µs ± 9% 20.3µs ± 2% +3.68% (p=0.019 n=9+5)
JavaStringLong 103µs ± 8% 24µs ± 4% -77.13% (p=0.001 n=9+5)
JavaStringLongDirect 113µs ± 9% 32µs ± 7% -71.63% (p=0.001 n=9+5)
JavaStringShortUnicode 11.1µs ±16% 10.7µs ± 5% ~ (p=0.190 n=9+5)
JavaStringShortUnicodeDirect 19.6µs ± 7% 20.2µs ± 1% +2.78% (p=0.029 n=9+5)
JavaStringLongUnicode 97.1µs ± 9% 28.0µs ± 5% -71.17% (p=0.001 n=9+5)
JavaStringLongUnicodeDirect 105µs ±10% 34µs ± 5% -67.23% (p=0.002 n=8+5)
JavaStringRetShort 14.2µs ± 2% 13.9µs ± 1% -2.15% (p=0.006 n=8+5)
JavaStringRetShortDirect 20.8µs ± 2% 20.4µs ± 2% ~ (p=0.065 n=8+5)
JavaStringRetLong 42.2µs ± 9% 42.4µs ± 3% ~ (p=0.190 n=9+5)
JavaStringRetLongDirect 51.2µs ±21% 50.8µs ± 8% ~ (p=0.518 n=9+5)
GoStringShort 23.4µs ± 7% 22.5µs ± 3% -3.55% (p=0.019 n=9+5)
GoStringLong 51.9µs ± 9% 53.1µs ± 3% ~ (p=0.240 n=9+5)
GoStringShortUnicode 24.2µs ± 6% 22.8µs ± 1% -5.54% (p=0.002 n=9+5)
GoStringLongUnicode 58.6µs ± 8% 57.6µs ± 3% ~ (p=0.518 n=9+5)
GoStringRetShort 27.6µs ± 1% 23.2µs ± 2% -15.87% (p=0.003 n=7+5)
GoStringRetLong 129µs ±12% 33µs ± 2% -74.03% (p=0.001 n=10+5)
Change-Id: Icb9481981493ffca8defed9fb80a9433d6048937
Reviewed-on: https://go-review.googlesource.com/20250
Reviewed-by: David Crawshaw <crawshaw@golang.org>
The seq serialization machinery is a historic artifact from when Go
mobile code had to run in a separate process. Now that Go code is running
in-process, replace the explicit serialization with direct calls and pass
arguments on the stack.
The benefits are a much smaller bind runtime, much less garbage (and, in
Java, fewer objects with finalizers), less argument copying, and faster
cross-language calls.
The cost is a more complex generator, because some of the work from the
bind runtime is moved to generated code. Generated code now handles
conversion between Go and Java/ObjC types, multiple return values and memory
management of byte slice and string arguments.
To overcome the lack of calling C code between Go packages, all bound
packages now end up in the same (fake) package, "gomobile_bind", instead of
separate packages (go_<pkgname>). To avoid name clashes, the package name is
added as a prefix to generated functions and types.
Also, don't copy byte arrays passed to Go, saving call time and
allowing read([]byte)-style interfaces to foreign callers (#12113).
Finally, add support for nil interfaces and struct pointers to objc.
This is a large CL, but most of the changes stem from changing testdata.
The full benchcmp output on the CL/20095 benchmarks on my Nexus 5 is
reproduced below. Note that the savings for the JavaSlice* benchmarks are
skewed because byte slices are no longer copied before passing them to Go.
benchmark old ns/op new ns/op delta
BenchmarkJavaEmpty 26.0 19.0 -26.92%
BenchmarkJavaEmptyDirect 23.0 22.0 -4.35%
BenchmarkJavaNoargs 7685 2339 -69.56%
BenchmarkJavaNoargsDirect 17405 8041 -53.80%
BenchmarkJavaOnearg 26887 2366 -91.20%
BenchmarkJavaOneargDirect 34266 7910 -76.92%
BenchmarkJavaOneret 38325 2245 -94.14%
BenchmarkJavaOneretDirect 46265 7708 -83.34%
BenchmarkJavaManyargs 41720 2535 -93.92%
BenchmarkJavaManyargsDirect 51026 8373 -83.59%
BenchmarkJavaRefjava 38139 21260 -44.26%
BenchmarkJavaRefjavaDirect 42706 28150 -34.08%
BenchmarkJavaRefgo 34403 6843 -80.11%
BenchmarkJavaRefgoDirect 40193 16582 -58.74%
BenchmarkJavaStringShort 32366 9323 -71.20%
BenchmarkJavaStringShortDirect 41973 19118 -54.45%
BenchmarkJavaStringLong 127879 94420 -26.16%
BenchmarkJavaStringLongDirect 133776 114760 -14.21%
BenchmarkJavaStringShortUnicode 32562 9221 -71.68%
BenchmarkJavaStringShortUnicodeDirect 41464 19094 -53.95%
BenchmarkJavaStringLongUnicode 131015 89401 -31.76%
BenchmarkJavaStringLongUnicodeDirect 134130 90786 -32.31%
BenchmarkJavaSliceShort 42462 7538 -82.25%
BenchmarkJavaSliceShortDirect 52940 17017 -67.86%
BenchmarkJavaSliceLong 138391 8466 -93.88%
BenchmarkJavaSliceLongDirect 205804 15666 -92.39%
BenchmarkGoEmpty 3.00 3.00 +0.00%
BenchmarkGoEmptyDirect 3.00 3.00 +0.00%
BenchmarkGoNoarg 40342 13716 -66.00%
BenchmarkGoNoargDirect 46691 13569 -70.94%
BenchmarkGoOnearg 43529 13757 -68.40%
BenchmarkGoOneargDirect 44867 14078 -68.62%
BenchmarkGoOneret 45456 13559 -70.17%
BenchmarkGoOneretDirect 44694 13442 -69.92%
BenchmarkGoRefjava 55111 28071 -49.06%
BenchmarkGoRefjavaDirect 60883 26872 -55.86%
BenchmarkGoRefgo 57038 29223 -48.77%
BenchmarkGoRefgoDirect 56153 27812 -50.47%
BenchmarkGoManyargs 67967 17398 -74.40%
BenchmarkGoManyargsDirect 60617 16998 -71.96%
BenchmarkGoStringShort 57538 22600 -60.72%
BenchmarkGoStringShortDirect 52627 22704 -56.86%
BenchmarkGoStringLong 128485 52530 -59.12%
BenchmarkGoStringLongDirect 138377 52079 -62.36%
BenchmarkGoStringShortUnicode 57062 22994 -59.70%
BenchmarkGoStringShortUnicodeDirect 62563 22938 -63.34%
BenchmarkGoStringLongUnicode 139913 55553 -60.29%
BenchmarkGoStringLongUnicodeDirect 150863 57791 -61.69%
BenchmarkGoSliceShort 59279 20215 -65.90%
BenchmarkGoSliceShortDirect 60160 21136 -64.87%
BenchmarkGoSliceLong 411225 301870 -26.59%
BenchmarkGoSliceLongDirect 399029 298915 -25.09%
Fixesgolang/go#12619Fixesgolang/go#12113Fixesgolang/go#13033
Change-Id: I2b45e9e98a1248e3c23a5137f775f7364908bec7
Reviewed-on: https://go-review.googlesource.com/19821
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
Elias Naur
Hyang-Ah (Hana) Kim