mirror of https://github.com/grpc/grpc.git
[promises] Add a switch primitive (#35424)
Remove the old `switch` library - this used to be an implementation detail of `Seq`, `TrySeq` - but has become unused.
Add a new user facing primitive `Switch` that fills a similar role to `switch` in C++ - selecting a promise to execute based on a primitive discriminator - much like `If` allows selection based on a boolean discriminator now.
A future change will optimize this to actually lower the `Switch` into an actual `switch` statement, but for right now I want to get the functionality in.
Closes #35424
COPYBARA_INTEGRATE_REVIEW=https://github.com/grpc/grpc/pull/35424 from ctiller:switchy 5308a914c6
PiperOrigin-RevId: 595140965
pull/35415/head
Craig Tiller
1 year ago
committed by
Copybara-Service
parent
1383c4629b
commit
75e5ebcb14
9 changed files with 241 additions and 1542 deletions
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// Copyright 2023 gRPC authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#ifndef GRPC_SRC_CORE_LIB_PROMISE_SWITCH_H |
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#define GRPC_SRC_CORE_LIB_PROMISE_SWITCH_H |
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#include <grpc/support/port_platform.h> |
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#include <memory> |
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#include <utility> |
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#include "src/core/lib/promise/detail/promise_factory.h" |
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#include "src/core/lib/promise/if.h" |
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namespace grpc_core { |
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namespace promise_detail { |
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template <typename D, typename F> |
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struct Case { |
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D discriminator; |
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F factory; |
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}; |
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template <typename F> |
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struct Default { |
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F factory; |
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}; |
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} // namespace promise_detail
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template <typename D, typename PromiseFactory> |
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auto Case(D discriminator, PromiseFactory f) { |
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return promise_detail::Case<D, PromiseFactory>{discriminator, std::move(f)}; |
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} |
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template <typename PromiseFactory> |
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auto Default(PromiseFactory f) { |
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return promise_detail::Default<PromiseFactory>{std::move(f)}; |
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} |
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// Given a list of cases that result in promise factories, return a single
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// promise chosen by the discriminator (the first argument of this function).
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// e.g.:
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// Switch(1, Case<1>([] { return 43; }), Case<2>([] { return 44; }))
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// resolves to 43.
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// TODO(ctiller): consider writing a code-generator like we do for seq/join
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// so that this lowers into a C switch statement.
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template <typename D, typename F> |
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auto Switch(D, promise_detail::Default<F> def) { |
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return promise_detail::OncePromiseFactory<void, F>(std::move(def.factory)) |
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.Make(); |
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} |
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template <typename D, typename F, typename... Others> |
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auto Switch(D discriminator, promise_detail::Case<D, F> c, Others... others) { |
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return If(discriminator == c.discriminator, std::move(c.factory), |
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Switch(discriminator, std::move(others)...)); |
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} |
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} // namespace grpc_core
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#endif // GRPC_SRC_CORE_LIB_PROMISE_SWITCH_H
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@ -0,0 +1,69 @@ |
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// Copyright 2023 gRPC authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#include "src/core/lib/promise/switch.h" |
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#include "gtest/gtest.h" |
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namespace grpc_core { |
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TEST(SwitchTest, JustDefault) { |
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EXPECT_EQ(Switch(42, Default([] { return 1; }))(), Poll<int>(1)); |
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} |
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TEST(SwitchTest, ThreeCases) { |
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auto test_switch = [](int d) { |
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return Switch(d, Case(1, [] { return 25; }), Case(2, [] { return 95; }), |
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Case(3, [] { return 68; }), Default([] { return 52; })); |
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}; |
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EXPECT_EQ(test_switch(0)(), Poll<int>(52)); |
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EXPECT_EQ(test_switch(1)(), Poll<int>(25)); |
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EXPECT_EQ(test_switch(2)(), Poll<int>(95)); |
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EXPECT_EQ(test_switch(3)(), Poll<int>(68)); |
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EXPECT_EQ(test_switch(4)(), Poll<int>(52)); |
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} |
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TEST(SwitchTest, Pending) { |
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auto test_switch = [](int d) { |
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return Switch(d, Case(42, []() -> Poll<int> { return Pending{}; }), |
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Case(1, [] { return 25; }), Case(2, [] { return 95; }), |
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Case(3, [] { return 68; }), Default([] { return 52; })); |
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}; |
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EXPECT_EQ(test_switch(0)(), Poll<int>(52)); |
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EXPECT_EQ(test_switch(1)(), Poll<int>(25)); |
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EXPECT_EQ(test_switch(2)(), Poll<int>(95)); |
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EXPECT_EQ(test_switch(3)(), Poll<int>(68)); |
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EXPECT_EQ(test_switch(4)(), Poll<int>(52)); |
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EXPECT_EQ(test_switch(42)(), Poll<int>(Pending{})); |
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} |
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TEST(SwitchTest, ThreeCasesFromEnum) { |
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enum class X : uint8_t { A, B, C }; |
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auto test_switch = [](X d) { |
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return Switch(d, Case(X::A, [] { return 25; }), |
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Case(X::B, [] { return 95; }), Case(X::C, [] { return 68; }), |
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Default([] { return 52; })); |
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}; |
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EXPECT_EQ(test_switch(X::A)(), Poll<int>(25)); |
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EXPECT_EQ(test_switch(X::B)(), Poll<int>(95)); |
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EXPECT_EQ(test_switch(X::C)(), Poll<int>(68)); |
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} |
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} // namespace grpc_core
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int main(int argc, char** argv) { |
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::testing::InitGoogleTest(&argc, argv); |
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return RUN_ALL_TESTS(); |
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} |
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@ -1,78 +0,0 @@ |
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#!/usr/bin/env python3 |
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# Copyright 2021 gRPC authors. |
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# |
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# Licensed under the Apache License, Version 2.0 (the "License"); |
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# you may not use this file except in compliance with the License. |
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# You may obtain a copy of the License at |
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# |
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# http://www.apache.org/licenses/LICENSE-2.0 |
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# |
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# Unless required by applicable law or agreed to in writing, software |
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# distributed under the License is distributed on an "AS IS" BASIS, |
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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# See the License for the specific language governing permissions and |
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# limitations under the License. |
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import sys |
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# utility: print a big comment block into a set of files |
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def put_banner(files, banner): |
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for f in files: |
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print("/*", file=f) |
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for line in banner: |
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print(" * %s" % line, file=f) |
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print(" */", file=f) |
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print("", file=f) |
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with open("src/core/lib/promise/detail/switch.h", "w") as H: |
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# copy-paste copyright notice from this file |
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with open(sys.argv[0]) as my_source: |
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copyright = [] |
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for line in my_source: |
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if line[0] != "#": |
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break |
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for line in my_source: |
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if line[0] == "#": |
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copyright.append(line) |
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break |
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for line in my_source: |
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if line[0] != "#": |
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break |
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copyright.append(line) |
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put_banner([H], [line[2:].rstrip() for line in copyright]) |
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put_banner([H], ["Automatically generated by %s" % sys.argv[0]]) |
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print("#ifndef GRPC_CORE_LIB_PROMISE_DETAIL_SWITCH_H", file=H) |
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print("#define GRPC_CORE_LIB_PROMISE_DETAIL_SWITCH_H", file=H) |
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print("", file=H) |
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print("#include <grpc/support/port_platform.h>", file=H) |
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print("", file=H) |
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print("#include <stdlib.h>", file=H) |
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print("", file=H) |
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print("namespace grpc_core {", file=H) |
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for n in range(1, 33): |
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print("", file=H) |
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print( |
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"template <typename R, %s> R Switch(char idx, %s) {" |
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% ( |
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", ".join("typename F%d" % i for i in range(0, n)), |
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", ".join("F%d f%d" % (i, i) for i in range(0, n)), |
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), |
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file=H, |
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) |
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print(" switch (idx) {", file=H) |
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for i in range(0, n): |
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print(" case %d: return f%d();" % (i, i), file=H) |
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print(" }", file=H) |
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print(" abort();", file=H) |
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print("}", file=H) |
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print("", file=H) |
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print("}", file=H) |
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print("", file=H) |
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print("#endif // GRPC_CORE_LIB_PROMISE_DETAIL_SWITCH_H", file=H) |
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