1 // Copyright 2018 Google Inc. 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 /////////////////////////////////////////////////////////////////////////////// 16 17 #ifndef TINK_UTIL_OSTREAM_OUTPUT_STREAM_H_ 18 #define TINK_UTIL_OSTREAM_OUTPUT_STREAM_H_ 19 20 #include <memory> 21 #include <ostream> 22 23 #include "tink/output_stream.h" 24 #include "tink/util/status.h" 25 #include "tink/util/statusor.h" 26 27 namespace crypto { 28 namespace tink { 29 namespace util { 30 31 // An OutputStream that writes to an ostream. 32 class OstreamOutputStream : public crypto::tink::OutputStream { 33 public: 34 // Constructs an OutputStream that will write to the ostream specified 35 // via 'output', using a buffer of the specified size, if any 36 // (if no legal 'buffer_size' is given, a reasonable default will be used). 37 explicit OstreamOutputStream(std::unique_ptr<std::ostream> output, 38 int buffer_size = -1); 39 40 ~OstreamOutputStream() override; 41 42 crypto::tink::util::StatusOr<int> Next(void** data) override; 43 44 void BackUp(int count) override; 45 46 crypto::tink::util::Status Close() override; 47 48 int64_t Position() const override; 49 50 private: 51 util::Status status_; 52 std::unique_ptr<std::ostream> output_; 53 std::unique_ptr<uint8_t[]> buffer_; 54 const int buffer_size_; 55 int64_t position_; // current position in the ostream (from the beginning) 56 57 // Counters that describe the state of the data in buffer_. 58 // count_in_buffer_ is always equal to (buffer_size_ - count_backedup_), 59 // except initially (before the first call to Next()). 60 // In other words, we have an invariant: 61 // (count_in_buffer_ == buffer_size_ - count_backedup_) || buffer_ == nullptr 62 int count_in_buffer_; // # bytes in buffer_ that will be eventually written 63 int count_backedup_; // # bytes in buffer_ that were backed up 64 int buffer_offset_; // offset where the returned *data starts in buffer_ 65 }; 66 67 } // namespace util 68 } // namespace tink 69 } // namespace crypto 70 71 #endif // TINK_UTIL_OSTREAM_OUTPUT_STREAM_H_ 72