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* Copyright 2017 The WebRTC project authors. All Rights Reserved.
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
#ifndef API_RTC_ERROR_H_
#define API_RTC_ERROR_H_
#include <ostream>
#include <string>
#include <utility> // For std::move.
#include "absl/strings/string_view.h"
#include "absl/types/optional.h"
#include "rtc_base/checks.h"
#include "rtc_base/logging.h"
#include "rtc_base/system/rtc_export.h"
namespace webrtc {
// Enumeration to represent distinct classes of errors that an application
// may wish to act upon differently. These roughly map to DOMExceptions or
// RTCError "errorDetailEnum" values in the web API, as described in the
// comments below.
enum class RTCErrorType {
// No error.
// An operation is valid, but currently unsupported.
// Maps to OperationError DOMException.
// A supplied parameter is valid, but currently unsupported.
// Maps to OperationError DOMException.
// General error indicating that a supplied parameter is invalid.
// Maps to InvalidAccessError or TypeError DOMException depending on context.
// Slightly more specific than INVALID_PARAMETER; a parameter's value was
// outside the allowed range.
// Maps to RangeError DOMException.
// Slightly more specific than INVALID_PARAMETER; an error occurred while
// parsing string input.
// Maps to SyntaxError DOMException.
// The object does not support this operation in its current state.
// Maps to InvalidStateError DOMException.
// An attempt was made to modify the object in an invalid way.
// Maps to InvalidModificationError DOMException.
// An error occurred within an underlying network protocol.
// Maps to NetworkError DOMException.
// Some resource has been exhausted; file handles, hardware resources, ports,
// etc.
// Maps to OperationError DOMException.
// The operation failed due to an internal error.
// Maps to OperationError DOMException.
// An error occured that has additional data.
// The additional data is specified in
// Maps to RTCError DOMException.
// Detail information, showing what further information should be present.
enum class RTCErrorDetailType {
// Roughly corresponds to RTCError in the web api. Holds an error type, a
// message, and possibly additional information specific to that error.
// Doesn't contain anything beyond a type and message now, but will in the
// future as more errors are implemented.
class RTC_EXPORT RTCError {
// Constructors.
// Creates a "no error" error.
RTCError() {}
explicit RTCError(RTCErrorType type) : type_(type) {}
RTCError(RTCErrorType type, absl::string_view message)
: type_(type), message_(message) {}
// In many use cases, it is better to use move than copy,
// but copy and assignment are provided for those cases that need it.
// Note that this has extra overhead because it copies strings.
RTCError(const RTCError& other) = default;
RTCError(RTCError&&) = default;
RTCError& operator=(const RTCError& other) = default;
RTCError& operator=(RTCError&&) = default;
// Identical to default constructed error.
// Preferred over the default constructor for code readability.
static RTCError OK();
// Error type.
RTCErrorType type() const { return type_; }
void set_type(RTCErrorType type) { type_ = type; }
// Human-readable message describing the error. Shouldn't be used for
// anything but logging/diagnostics, since messages are not guaranteed to be
// stable.
const char* message() const;
void set_message(absl::string_view message);
RTCErrorDetailType error_detail() const { return error_detail_; }
void set_error_detail(RTCErrorDetailType detail) { error_detail_ = detail; }
absl::optional<uint16_t> sctp_cause_code() const { return sctp_cause_code_; }
void set_sctp_cause_code(uint16_t cause_code) {
sctp_cause_code_ = cause_code;
// Convenience method for situations where you only care whether or not an
// error occurred.
bool ok() const { return type_ == RTCErrorType::NONE; }
RTCErrorType type_ = RTCErrorType::NONE;
std::string message_;
RTCErrorDetailType error_detail_ = RTCErrorDetailType::NONE;
absl::optional<uint16_t> sctp_cause_code_;
// Outputs the error as a friendly string. Update this method when adding a new
// error type.
// Only intended to be used for logging/diagnostics. The returned char* points
// to literal string that lives for the whole duration of the program.
RTC_EXPORT absl::string_view ToString(RTCErrorType error);
RTC_EXPORT absl::string_view ToString(RTCErrorDetailType error);
inline std::ostream& operator<<( // no-presubmit-check TODO(webrtc:8982)
std::ostream& stream, // no-presubmit-check TODO(webrtc:8982)
RTCErrorType error) {
return stream << ToString(error);
inline std::ostream& operator<<( // no-presubmit-check TODO(webrtc:8982)
std::ostream& stream, // no-presubmit-check TODO(webrtc:8982)
RTCErrorDetailType error) {
return stream << ToString(error);
// Helper macro that can be used by implementations to create an error with a
// message and log it. `message` should be a string literal or movable
// std::string.
#define LOG_AND_RETURN_ERROR_EX(type, message, severity) \
{ \
RTC_DCHECK(type != RTCErrorType::NONE); \
RTC_LOG(severity) << message << " (" << ::webrtc::ToString(type) << ")"; \
return ::webrtc::RTCError(type, message); \
#define LOG_AND_RETURN_ERROR(type, message) \
// RTCErrorOr<T> is the union of an RTCError object and a T object. RTCErrorOr
// models the concept of an object that is either a usable value, or an error
// Status explaining why such a value is not present. To this end RTCErrorOr<T>
// does not allow its RTCErrorType value to be RTCErrorType::NONE. This is
// enforced by a debug check in most cases.
// The primary use-case for RTCErrorOr<T> is as the return value of a function
// which may fail. For example, CreateRtpSender will fail if the parameters
// could not be successfully applied at the media engine level, but if
// successful will return a unique_ptr to an RtpSender.
// Example client usage for a RTCErrorOr<std::unique_ptr<T>>:
// RTCErrorOr<std::unique_ptr<Foo>> result = FooFactory::MakeNewFoo(arg);
// if (result.ok()) {
// std::unique_ptr<Foo> foo = result.ConsumeValue();
// foo->DoSomethingCool();
// } else {
// RTC_LOG(LS_ERROR) << result.error();
// }
// Example factory implementation returning RTCErrorOr<std::unique_ptr<T>>:
// RTCErrorOr<std::unique_ptr<Foo>> FooFactory::MakeNewFoo(int arg) {
// if (arg <= 0) {
// return RTCError(RTCErrorType::INVALID_RANGE, "Arg must be positive");
// } else {
// return std::unique_ptr<Foo>(new Foo(arg));
// }
// }
template <typename T>
class RTCErrorOr {
// Used to convert between RTCErrorOr<Foo>/RtcErrorOr<Bar>, when an implicit
// conversion from Foo to Bar exists.
template <typename U>
friend class RTCErrorOr;
typedef T element_type;
// Constructs a new RTCErrorOr with RTCErrorType::INTERNAL_ERROR error. This
// is marked 'explicit' to try to catch cases like 'return {};', where people
// think RTCErrorOr<std::vector<int>> will be initialized with an empty
// vector, instead of a RTCErrorType::INTERNAL_ERROR error.
RTCErrorOr() : error_(RTCErrorType::INTERNAL_ERROR) {}
// Constructs a new RTCErrorOr with the given non-ok error. After calling
// this constructor, calls to value() will DCHECK-fail.
// NOTE: Not explicit - we want to use RTCErrorOr<T> as a return
// value, so it is convenient and sensible to be able to do 'return
// RTCError(...)' when the return type is RTCErrorOr<T>.
// REQUIRES: !error.ok(). This requirement is DCHECKed.
RTCErrorOr(RTCError&& error) : error_(std::move(error)) { // NOLINT
// Constructs a new RTCErrorOr with the given value. After calling this
// constructor, calls to value() will succeed, and calls to error() will
// return a default-constructed RTCError.
// NOTE: Not explicit - we want to use RTCErrorOr<T> as a return type
// so it is convenient and sensible to be able to do 'return T()'
// when the return type is RTCErrorOr<T>.
RTCErrorOr(const T& value) : value_(value) {} // NOLINT
RTCErrorOr(T&& value) : value_(std::move(value)) {} // NOLINT
// Delete the copy constructor and assignment operator; there aren't any use
// cases where you should need to copy an RTCErrorOr, as opposed to moving
// it. Can revisit this decision if use cases arise in the future.
RTCErrorOr(const RTCErrorOr& other) = delete;
RTCErrorOr& operator=(const RTCErrorOr& other) = delete;
// Move constructor and move-assignment operator.
// Visual Studio doesn't support "= default" with move constructors or
// assignment operators (even though they compile, they segfault), so define
// them explicitly.
RTCErrorOr(RTCErrorOr&& other)
: error_(std::move(other.error_)), value_(std::move(other.value_)) {}
RTCErrorOr& operator=(RTCErrorOr&& other) {
error_ = std::move(other.error_);
value_ = std::move(other.value_);
return *this;
// Conversion constructor and assignment operator; T must be copy or move
// constructible from U.
template <typename U>
RTCErrorOr(RTCErrorOr<U> other) // NOLINT
: error_(std::move(other.error_)), value_(std::move(other.value_)) {}
template <typename U>
RTCErrorOr& operator=(RTCErrorOr<U> other) {
error_ = std::move(other.error_);
value_ = std::move(other.value_);
return *this;
// Returns a reference to our error. If this contains a T, then returns
// default-constructed RTCError.
const RTCError& error() const { return error_; }
// Moves the error. Can be useful if, say "CreateFoo" returns an
// RTCErrorOr<Foo>, and internally calls "CreateBar" which returns an
// RTCErrorOr<Bar>, and wants to forward the error up the stack.
RTCError MoveError() { return std::move(error_); }
// Returns this->error().ok()
bool ok() const { return error_.ok(); }
// Returns a reference to our current value, or DCHECK-fails if !this->ok().
// Can be convenient for the implementation; for example, a method may want
// to access the value in some way before returning it to the next method on
// the stack.
const T& value() const {
return *value_;
T& value() {
return *value_;
// Moves our current value out of this object and returns it, or DCHECK-fails
// if !this->ok().
T MoveValue() {
return std::move(*value_);
RTCError error_;
absl::optional<T> value_;
} // namespace webrtc
#endif // API_RTC_ERROR_H_