unplugged-system/device/google/cuttlefish/common/libs/utils/result.h

329 lines
11 KiB
C++

//
// Copyright (C) 2022 The Android Open Source Project
//
// 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.
#pragma once
#include <optional>
#include <type_traits>
#include <android-base/logging.h>
#include <android-base/result.h> // IWYU pragma: export
namespace cuttlefish {
class StackTraceError;
class StackTraceEntry {
public:
StackTraceEntry(std::string file, size_t line, std::string pretty_function)
: file_(std::move(file)),
line_(line),
pretty_function_(std::move(pretty_function)) {}
StackTraceEntry(std::string file, size_t line, std::string pretty_function,
std::string expression)
: file_(std::move(file)),
line_(line),
pretty_function_(std::move(pretty_function)),
expression_(std::move(expression)) {}
StackTraceEntry(const StackTraceEntry& other)
: file_(other.file_),
line_(other.line_),
pretty_function_(other.pretty_function_),
expression_(other.expression_),
message_(other.message_.str()) {}
StackTraceEntry(StackTraceEntry&&) = default;
StackTraceEntry& operator=(const StackTraceEntry& other) {
file_ = other.file_;
line_ = other.line_;
pretty_function_ = other.pretty_function_;
expression_ = other.expression_;
message_.str(other.message_.str());
return *this;
}
StackTraceEntry& operator=(StackTraceEntry&&) = default;
template <typename T>
StackTraceEntry& operator<<(T&& message_ext) & {
message_ << std::forward<T>(message_ext);
return *this;
}
template <typename T>
StackTraceEntry operator<<(T&& message_ext) && {
message_ << std::forward<T>(message_ext);
return std::move(*this);
}
operator StackTraceError() &&;
template <typename T>
operator android::base::expected<T, StackTraceError>() &&;
bool HasMessage() const { return !message_.str().empty(); }
void Write(std::ostream& stream) const { stream << message_.str(); }
void WriteVerbose(std::ostream& stream) const {
auto str = message_.str();
if (str.empty()) {
stream << "Failure\n";
} else {
stream << message_.str() << "\n";
}
stream << " at " << file_ << ":" << line_ << "\n";
stream << " in " << pretty_function_;
if (!expression_.empty()) {
stream << " for CF_EXPECT(" << expression_ << ")\n";
}
}
private:
std::string file_;
size_t line_;
std::string pretty_function_;
std::string expression_;
std::stringstream message_;
};
#define CF_STACK_TRACE_ENTRY(expression) \
StackTraceEntry(__FILE__, __LINE__, __PRETTY_FUNCTION__, expression)
class StackTraceError {
public:
StackTraceError& PushEntry(StackTraceEntry entry) & {
stack_.emplace_back(std::move(entry));
return *this;
}
StackTraceError PushEntry(StackTraceEntry entry) && {
stack_.emplace_back(std::move(entry));
return std::move(*this);
}
const std::vector<StackTraceEntry>& Stack() const { return stack_; }
std::string Message() const {
std::stringstream writer;
for (const auto& entry : stack_) {
entry.Write(writer);
}
return writer.str();
}
std::string Trace() const {
std::stringstream writer;
for (const auto& entry : stack_) {
entry.WriteVerbose(writer);
}
return writer.str();
}
template <typename T>
operator android::base::expected<T, StackTraceError>() && {
return android::base::unexpected(std::move(*this));
}
private:
std::vector<StackTraceEntry> stack_;
};
inline StackTraceEntry::operator StackTraceError() && {
return StackTraceError().PushEntry(std::move(*this));
}
template <typename T>
inline StackTraceEntry::operator android::base::expected<T,
StackTraceError>() && {
return android::base::unexpected(std::move(*this));
}
template <typename T>
using Result = android::base::expected<T, StackTraceError>;
/**
* Error return macro that includes the location in the file in the error
* message. Use CF_ERRNO when including information from errno, otherwise use
* the base CF_ERR macro.
*
* Example usage:
*
* if (mkdir(path.c_str()) != 0) {
* return CF_ERRNO("mkdir(\"" << path << "\") failed: "
* << strerror(errno));
* }
*
* This will return an error with the text
*
* mkdir(...) failed: ...
* at path/to/file.cpp:50
* in Result<std::string> MyFunction()
*/
#define CF_ERR(MSG) (CF_STACK_TRACE_ENTRY("") << MSG)
#define CF_ERRNO(MSG) (CF_STACK_TRACE_ENTRY("") << MSG)
template <typename T>
T OutcomeDereference(std::optional<T>&& value) {
return std::move(*value);
}
template <typename T>
typename std::conditional_t<std::is_void_v<T>, bool, T> OutcomeDereference(
Result<T>&& result) {
if constexpr (std::is_void<T>::value) {
return result.ok();
} else {
return std::move(*result);
}
}
template <typename T>
typename std::enable_if<std::is_convertible_v<T, bool>, T>::type
OutcomeDereference(T&& value) {
return std::forward<T>(value);
}
inline bool TypeIsSuccess(bool value) { return value; }
template <typename T>
bool TypeIsSuccess(std::optional<T>& value) {
return value.has_value();
}
template <typename T>
bool TypeIsSuccess(Result<T>& value) {
return value.ok();
}
template <typename T>
bool TypeIsSuccess(Result<T>&& value) {
return value.ok();
}
inline auto ErrorFromType(bool) { return StackTraceError(); }
template <typename T>
inline auto ErrorFromType(std::optional<T>) {
return StackTraceError();
}
template <typename T>
auto ErrorFromType(Result<T>& value) {
return value.error();
}
template <typename T>
auto ErrorFromType(Result<T>&& value) {
return value.error();
}
#define CF_EXPECT_OVERLOAD(_1, _2, NAME, ...) NAME
#define CF_EXPECT2(RESULT, MSG) \
({ \
decltype(RESULT)&& macro_intermediate_result = RESULT; \
if (!TypeIsSuccess(macro_intermediate_result)) { \
auto current_entry = CF_STACK_TRACE_ENTRY(#RESULT); \
current_entry << MSG; \
auto error = ErrorFromType(macro_intermediate_result); \
error.PushEntry(std::move(current_entry)); \
return error; \
}; \
OutcomeDereference(std::move(macro_intermediate_result)); \
})
#define CF_EXPECT1(RESULT) CF_EXPECT2(RESULT, "")
/**
* Error propagation macro that can be used as an expression.
*
* The first argument can be either a Result or a type that is convertible to
* a boolean. A successful result will return the value inside the result, or
* a conversion to a `true` value will return the unconverted value. This is
* useful for e.g. pointers which can be tested through boolean conversion.
*
* In the failure case, this macro will return from the containing function
* with a failing Result. The failing result will include information about the
* call site, details from the optional second argument if given, and details
* from the failing inner expression if it is a Result.
*
* This macro must be invoked only in functions that return a Result.
*
* Example usage:
*
* Result<std::string> CreateTempDir();
*
* Result<std::string> CreatePopulatedTempDir() {
* std::string dir = CF_EXPECT(CreateTempDir(), "Failed to create dir");
* // Do something with dir
* return dir;
* }
*
* If CreateTempDir fails, the function will returna Result with an error
* message that looks like
*
* Internal error
* at /path/to/otherfile.cpp:50
* in Result<std::string> CreateTempDir()
* Failed to create dir
* at /path/to/file.cpp:81:
* in Result<std::string> CreatePopulatedTempDir()
* for CF_EXPECT(CreateTempDir())
*/
#define CF_EXPECT(...) \
CF_EXPECT_OVERLOAD(__VA_ARGS__, CF_EXPECT2, CF_EXPECT1)(__VA_ARGS__)
#define CF_COMPARE_EXPECT4(COMPARE_OP, LHS_RESULT, RHS_RESULT, MSG) \
({ \
auto&& lhs_macro_intermediate_result = LHS_RESULT; \
auto&& rhs_macro_intermediate_result = RHS_RESULT; \
bool comparison_result = lhs_macro_intermediate_result COMPARE_OP \
rhs_macro_intermediate_result; \
if (!comparison_result) { \
auto current_entry = CF_STACK_TRACE_ENTRY(""); \
current_entry << "Expected \"" << #LHS_RESULT << "\" " << #COMPARE_OP \
<< " \"" << #RHS_RESULT << "\" but was " \
<< lhs_macro_intermediate_result << " vs " \
<< rhs_macro_intermediate_result << "."; \
current_entry << MSG; \
auto error = ErrorFromType(false); \
error.PushEntry(std::move(current_entry)); \
return error; \
}; \
comparison_result; \
})
#define CF_COMPARE_EXPECT3(COMPARE_OP, LHS_RESULT, RHS_RESULT) \
CF_COMPARE_EXPECT4(COMPARE_OP, LHS_RESULT, RHS_RESULT, "")
#define CF_COMPARE_EXPECT_OVERLOAD(_1, _2, _3, _4, NAME, ...) NAME
#define CF_COMPARE_EXPECT(...) \
CF_COMPARE_EXPECT_OVERLOAD(__VA_ARGS__, CF_COMPARE_EXPECT4, \
CF_COMPARE_EXPECT3) \
(__VA_ARGS__)
#define CF_EXPECT_EQ(LHS_RESULT, RHS_RESULT, ...) \
CF_COMPARE_EXPECT(==, LHS_RESULT, RHS_RESULT, ##__VA_ARGS__)
#define CF_EXPECT_NE(LHS_RESULT, RHS_RESULT, ...) \
CF_COMPARE_EXPECT(!=, LHS_RESULT, RHS_RESULT, ##__VA_ARGS__)
#define CF_EXPECT_LE(LHS_RESULT, RHS_RESULT, ...) \
CF_COMPARE_EXPECT(<=, LHS_RESULT, RHS_RESULT, ##__VA_ARGS__)
#define CF_EXPECT_LT(LHS_RESULT, RHS_RESULT, ...) \
CF_COMPARE_EXPECT(<, LHS_RESULT, RHS_RESULT, ##__VA_ARGS__)
#define CF_EXPECT_GE(LHS_RESULT, RHS_RESULT, ...) \
CF_COMPARE_EXPECT(>=, LHS_RESULT, RHS_RESULT, ##__VA_ARGS__)
#define CF_EXPECT_GT(LHS_RESULT, RHS_RESULT, ...) \
CF_COMPARE_EXPECT(>, LHS_RESULT, RHS_RESULT, ##__VA_ARGS__)
} // namespace cuttlefish