1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
|
// Copyright 2021 gRPC authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#ifndef GRPC_SRC_CORE_LIB_PROMISE_TRY_SEQ_H
#define GRPC_SRC_CORE_LIB_PROMISE_TRY_SEQ_H
#include <grpc/support/port_platform.h>
#include <type_traits>
#include <utility>
#include "y_absl/meta/type_traits.h"
#include "y_absl/status/status.h"
#include "y_absl/status/statusor.h"
#include "src/core/lib/promise/detail/basic_seq.h"
#include "src/core/lib/promise/detail/promise_like.h"
#include "src/core/lib/promise/detail/status.h"
#include "src/core/lib/promise/poll.h"
namespace grpc_core {
namespace promise_detail {
template <typename T, typename Ignored = void>
struct TrySeqTraitsWithSfinae {
using UnwrappedType = T;
using WrappedType = y_absl::StatusOr<T>;
template <typename Next>
static auto CallFactory(Next* next, T&& value) {
return next->Make(std::forward<T>(value));
}
template <typename F, typename Elem>
static auto CallSeqFactory(F& f, Elem&& elem, T&& value)
-> decltype(f(std::forward<Elem>(elem), std::forward<T>(value))) {
return f(std::forward<Elem>(elem), std::forward<T>(value));
}
template <typename Result, typename RunNext>
static Poll<Result> CheckResultAndRunNext(T prior, RunNext run_next) {
return run_next(std::move(prior));
}
};
template <typename T>
struct TrySeqTraitsWithSfinae<y_absl::StatusOr<T>> {
using UnwrappedType = T;
using WrappedType = y_absl::StatusOr<T>;
template <typename Next>
static auto CallFactory(Next* next, y_absl::StatusOr<T>&& status) {
return next->Make(std::move(*status));
}
template <typename F, typename Elem>
static auto CallSeqFactory(F& f, Elem&& elem, y_absl::StatusOr<T> value)
-> decltype(f(std::forward<Elem>(elem), std::move(*value))) {
return f(std::forward<Elem>(elem), std::move(*value));
}
template <typename Result, typename RunNext>
static Poll<Result> CheckResultAndRunNext(y_absl::StatusOr<T> prior,
RunNext run_next) {
if (!prior.ok()) return StatusCast<Result>(prior.status());
return run_next(std::move(prior));
}
};
// If there exists a function 'IsStatusOk(const T&) -> bool' then we assume that
// T is a status type for the purposes of promise sequences, and a non-OK T
// should terminate the sequence and return.
template <typename T>
struct TrySeqTraitsWithSfinae<
T, y_absl::enable_if_t<
std::is_same<decltype(IsStatusOk(std::declval<T>())), bool>::value,
void>> {
using UnwrappedType = void;
using WrappedType = T;
template <typename Next>
static auto CallFactory(Next* next, T&&) {
return next->Make();
}
template <typename Result, typename RunNext>
static Poll<Result> CheckResultAndRunNext(T prior, RunNext run_next) {
if (!IsStatusOk(prior)) return Result(std::move(prior));
return run_next(std::move(prior));
}
};
template <>
struct TrySeqTraitsWithSfinae<y_absl::Status> {
using UnwrappedType = void;
using WrappedType = y_absl::Status;
template <typename Next>
static auto CallFactory(Next* next, y_absl::Status&&) {
return next->Make();
}
template <typename Result, typename RunNext>
static Poll<Result> CheckResultAndRunNext(y_absl::Status prior,
RunNext run_next) {
if (!prior.ok()) return StatusCast<Result>(std::move(prior));
return run_next(std::move(prior));
}
};
template <typename T>
using TrySeqTraits = TrySeqTraitsWithSfinae<T>;
template <typename... Fs>
using TrySeq = BasicSeq<TrySeqTraits, Fs...>;
template <typename I, typename F, typename Arg>
struct TrySeqIterTraits {
using Iter = I;
using Factory = F;
using Argument = Arg;
using IterValue = decltype(*std::declval<Iter>());
using StateCreated = decltype(std::declval<F>()(std::declval<IterValue>(),
std::declval<Arg>()));
using State = PromiseLike<StateCreated>;
using Wrapped = typename State::Result;
using Traits = TrySeqTraits<Wrapped>;
};
template <typename Iter, typename Factory, typename Argument>
struct TrySeqIterResultTraits {
using IterTraits = TrySeqIterTraits<Iter, Factory, Argument>;
using Result = BasicSeqIter<IterTraits>;
};
} // namespace promise_detail
// Try a sequence of operations.
// * Run the first functor as a promise.
// * Feed its success result into the second functor to create a promise,
// then run that.
// * ...
// * Feed the second-final success result into the final functor to create a
// promise, then run that, with the overall success result being that
// promises success result.
// If any step fails, fail everything.
// Functors can return StatusOr<> to signal that a value is fed forward, or
// Status to indicate only success/failure. In the case of returning Status,
// the construction functors take no arguments.
template <typename... Functors>
promise_detail::TrySeq<Functors...> TrySeq(Functors... functors) {
return promise_detail::TrySeq<Functors...>(std::move(functors)...);
}
// Try a sequence of operations of unknown length.
// Asynchronously:
// for (element in (begin, end)) {
// auto r = wait_for factory(element, argument);
// if (!r.ok()) return r;
// argument = *r;
// }
// return argument;
template <typename Iter, typename Factory, typename Argument>
typename promise_detail::TrySeqIterResultTraits<Iter, Factory, Argument>::Result
TrySeqIter(Iter begin, Iter end, Argument argument, Factory factory) {
using Result =
typename promise_detail::TrySeqIterResultTraits<Iter, Factory,
Argument>::Result;
return Result(begin, end, std::move(factory), std::move(argument));
}
} // namespace grpc_core
#endif // GRPC_SRC_CORE_LIB_PROMISE_TRY_SEQ_H
|
