x/mobile/bind: byte slice parameter support without copy #12113
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hyangah
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Aug 11, 2015
Also mention the current limitation in byte slice binding. golang/go#12113. Change-Id: Ie75780c2d203431ca26a188dfdb8f000f6805c18 Reviewed-on: https://go-review.googlesource.com/13531 Reviewed-by: David Crawshaw <crawshaw@golang.org>
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I plan to work on this in Nov. |
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CL https://golang.org/cl/19821 mentions this issue. |
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Hello, I created a golang function with returntype array my golang function is } and after this i run the bind command it generate the framework and show header file with following result. |
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Gomobile does not (yet) support binding to function that takes or returns slices or arrays. If you need access to a Go slice or array from native code, use something like: Please use the golang-nuts discussion group for support questions in the future: |
imWildCat
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Apr 10, 2021
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% Fixes golang/go#12619 Fixes golang/go#12113 Fixes golang/go#13033 Change-Id: I2b45e9e98a1248e3c23a5137f775f7364908bec7 Reviewed-on: https://go-review.googlesource.com/19821 Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
imWildCat
pushed a commit
to imWildCat/go-mobile
that referenced
this issue
Apr 11, 2021
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% Fixes golang/go#12619 Fixes golang/go#12113 Fixes golang/go#13033 Change-Id: I2b45e9e98a1248e3c23a5137f775f7364908bec7 Reviewed-on: https://go-review.googlesource.com/19821 Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
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When a Go function or method taking a byte slice is called, the current implementation
creates a copy of the arguments and passes it to the Go function. The implementation
was based on the assumption that the Go function is free to keep the slice for later use.
This prevents implementation like io.Read([]byte) where the parameter's content
is modified during call. Moreover, it costs an extra copy & memory which can be significant
depending on the byte slice size.
Instead, I propose to pass a slice backed by the foreign language's byte array if possible.
Users who want to keep the slice for later use have to be aware of the limitation and somehow
create a copy for now.
More discussion on automation or tool support to detect such use cases
(another kind of escape analysis) is welcome.
@crawshaw
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