1 // Copyright 2020 The Tint Authors 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // http://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 15 #ifndef SRC_READER_SPIRV_FAIL_STREAM_H_ 16 #define SRC_READER_SPIRV_FAIL_STREAM_H_ 17 18 #include <ostream> 19 20 namespace tint { 21 namespace reader { 22 namespace spirv { 23 24 /// A FailStream object accumulates values onto a given std::ostream, 25 /// and can be used to record failure by writing the false value 26 /// to given a pointer-to-bool. 27 class FailStream { 28 public: 29 /// Creates a new fail stream 30 /// @param status_ptr where we will write false to indicate failure. Assumed 31 /// to be a valid pointer to bool. 32 /// @param out output stream where a message should be written to explain 33 /// the failure FailStream(bool * status_ptr,std::ostream * out)34 FailStream(bool* status_ptr, std::ostream* out) 35 : status_ptr_(status_ptr), out_(out) {} 36 /// Copy constructor 37 /// @param other the fail stream to clone 38 FailStream(const FailStream& other) = default; 39 40 /// Converts to a boolean status. A true result indicates success, 41 /// and a false result indicates failure. 42 /// @returns the status 43 operator bool() const { return *status_ptr_; } 44 /// Returns the current status value. This can be more readable 45 /// the conversion operator. 46 /// @returns the status status()47 bool status() const { return *status_ptr_; } 48 49 /// Records failure. 50 /// @returns a FailStream Fail()51 FailStream& Fail() { 52 *status_ptr_ = false; 53 return *this; 54 } 55 56 /// Appends the given value to the message output stream. 57 /// @param val the value to write to the output stream. 58 /// @returns this object 59 template <typename T> 60 FailStream& operator<<(const T& val) { 61 *out_ << val; 62 return *this; 63 } 64 65 private: 66 bool* status_ptr_; 67 std::ostream* out_; 68 }; 69 70 } // namespace spirv 71 } // namespace reader 72 } // namespace tint 73 74 #endif // SRC_READER_SPIRV_FAIL_STREAM_H_ 75