Alexei Frolov | dea46f7 | 2020-01-07 13:28:24 -0800 | [diff] [blame] | 1 | // Copyright 2020 The Pigweed Authors |
| 2 | // |
| 3 | // Licensed under the Apache License, Version 2.0 (the "License"); you may not |
| 4 | // use this file except in compliance with the License. You may obtain a copy of |
| 5 | // the License at |
| 6 | // |
| 7 | // https://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, WITHOUT |
| 11 | // WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the |
| 12 | // License for the specific language governing permissions and limitations under |
| 13 | // the License. |
| 14 | |
| 15 | #include "pw_protobuf/decoder.h" |
| 16 | |
Alexei Frolov | 6d9b9b4 | 2020-01-14 12:57:33 -0800 | [diff] [blame^] | 17 | #include <cstring> |
| 18 | |
Alexei Frolov | dea46f7 | 2020-01-07 13:28:24 -0800 | [diff] [blame] | 19 | #include "pw_varint/varint.h" |
| 20 | |
| 21 | namespace pw::protobuf { |
| 22 | |
| 23 | Status Decoder::Decode(span<const std::byte> proto) { |
| 24 | if (handler_ == nullptr || state_ != kReady) { |
| 25 | return Status::FAILED_PRECONDITION; |
| 26 | } |
| 27 | |
| 28 | state_ = kDecodeInProgress; |
| 29 | proto_ = proto; |
| 30 | |
| 31 | // Iterate over each field in the proto, calling the handler with the field |
| 32 | // key. |
| 33 | while (state_ == kDecodeInProgress && !proto_.empty()) { |
| 34 | const std::byte* original_cursor = proto_.data(); |
| 35 | |
| 36 | uint64_t key; |
| 37 | size_t bytes_read = varint::Decode(proto_, &key); |
| 38 | if (bytes_read == 0) { |
| 39 | state_ = kDecodeFailed; |
| 40 | return Status::DATA_LOSS; |
| 41 | } |
| 42 | |
| 43 | uint32_t field_number = key >> kFieldNumberShift; |
| 44 | Status status = handler_->ProcessField(this, field_number); |
| 45 | if (!status.ok()) { |
| 46 | return status; |
| 47 | } |
| 48 | |
| 49 | // The callback function can modify the decoder's state; check that |
| 50 | // everything is still okay. |
| 51 | if (state_ == kDecodeFailed) { |
| 52 | break; |
| 53 | } |
| 54 | |
| 55 | // If the cursor has not moved, the user has not consumed the field in their |
| 56 | // callback. Skip ahead to the next field. |
| 57 | if (original_cursor == proto_.data()) { |
| 58 | SkipField(); |
| 59 | } |
| 60 | } |
| 61 | |
| 62 | if (state_ != kDecodeInProgress) { |
| 63 | return Status::DATA_LOSS; |
| 64 | } |
| 65 | |
| 66 | state_ = kReady; |
| 67 | return Status::OK; |
| 68 | } |
| 69 | |
| 70 | Status Decoder::ReadVarint(uint32_t field_number, uint64_t* out) { |
Alexei Frolov | 6d9b9b4 | 2020-01-14 12:57:33 -0800 | [diff] [blame^] | 71 | Status status = ConsumeKey(field_number, WireType::kVarint); |
| 72 | if (!status.ok()) { |
| 73 | return status; |
| 74 | } |
| 75 | |
| 76 | size_t bytes_read = varint::Decode(proto_, out); |
| 77 | if (bytes_read == 0) { |
| 78 | state_ = kDecodeFailed; |
| 79 | return Status::DATA_LOSS; |
| 80 | } |
| 81 | |
| 82 | // Advance to the next field. |
| 83 | proto_ = proto_.subspan(bytes_read); |
| 84 | return Status::OK; |
| 85 | } |
| 86 | |
| 87 | Status Decoder::ReadFixed(uint32_t field_number, std::byte* out, size_t size) { |
| 88 | WireType expected_wire_type = |
| 89 | size == sizeof(uint32_t) ? WireType::kFixed32 : WireType::kFixed64; |
| 90 | Status status = ConsumeKey(field_number, expected_wire_type); |
| 91 | if (!status.ok()) { |
| 92 | return status; |
| 93 | } |
| 94 | |
| 95 | if (proto_.size() < size) { |
| 96 | return Status::DATA_LOSS; |
| 97 | } |
| 98 | |
| 99 | std::memcpy(out, proto_.data(), size); |
| 100 | proto_ = proto_.subspan(size); |
| 101 | |
| 102 | return Status::OK; |
| 103 | } |
| 104 | |
| 105 | Status Decoder::ReadDelimited(uint32_t field_number, |
| 106 | span<const std::byte>* out) { |
| 107 | Status status = ConsumeKey(field_number, WireType::kDelimited); |
| 108 | if (!status.ok()) { |
| 109 | return status; |
| 110 | } |
| 111 | |
| 112 | uint64_t length; |
| 113 | size_t bytes_read = varint::Decode(proto_, &length); |
| 114 | if (bytes_read == 0) { |
| 115 | state_ = kDecodeFailed; |
| 116 | return Status::DATA_LOSS; |
| 117 | } |
| 118 | |
| 119 | proto_ = proto_.subspan(bytes_read); |
| 120 | if (proto_.size() < length) { |
| 121 | state_ = kDecodeFailed; |
| 122 | return Status::DATA_LOSS; |
| 123 | } |
| 124 | |
| 125 | *out = proto_.first(length); |
| 126 | proto_ = proto_.subspan(length); |
| 127 | |
| 128 | return Status::OK; |
| 129 | } |
| 130 | |
| 131 | Status Decoder::ConsumeKey(uint32_t field_number, WireType expected_type) { |
Alexei Frolov | dea46f7 | 2020-01-07 13:28:24 -0800 | [diff] [blame] | 132 | if (state_ != kDecodeInProgress) { |
| 133 | return Status::FAILED_PRECONDITION; |
| 134 | } |
| 135 | |
| 136 | uint64_t key; |
| 137 | size_t bytes_read = varint::Decode(proto_, &key); |
| 138 | if (bytes_read == 0) { |
| 139 | state_ = kDecodeFailed; |
| 140 | return Status::FAILED_PRECONDITION; |
| 141 | } |
| 142 | |
| 143 | uint32_t field = key >> kFieldNumberShift; |
| 144 | WireType wire_type = static_cast<WireType>(key & kWireTypeMask); |
| 145 | |
Alexei Frolov | 6d9b9b4 | 2020-01-14 12:57:33 -0800 | [diff] [blame^] | 146 | if (field != field_number || wire_type != expected_type) { |
Alexei Frolov | dea46f7 | 2020-01-07 13:28:24 -0800 | [diff] [blame] | 147 | state_ = kDecodeFailed; |
| 148 | return Status::FAILED_PRECONDITION; |
| 149 | } |
| 150 | |
Alexei Frolov | 6d9b9b4 | 2020-01-14 12:57:33 -0800 | [diff] [blame^] | 151 | // Advance past the key. |
Alexei Frolov | dea46f7 | 2020-01-07 13:28:24 -0800 | [diff] [blame] | 152 | proto_ = proto_.subspan(bytes_read); |
| 153 | return Status::OK; |
| 154 | } |
| 155 | |
| 156 | void Decoder::SkipField() { |
| 157 | uint64_t key; |
| 158 | proto_ = proto_.subspan(varint::Decode(proto_, &key)); |
| 159 | |
| 160 | WireType wire_type = static_cast<WireType>(key & kWireTypeMask); |
| 161 | size_t bytes_to_skip = 0; |
| 162 | uint64_t value = 0; |
| 163 | |
| 164 | switch (wire_type) { |
| 165 | case WireType::kVarint: |
| 166 | bytes_to_skip = varint::Decode(proto_, &value); |
| 167 | break; |
| 168 | |
| 169 | case WireType::kDelimited: |
| 170 | // Varint at cursor indicates size of the field. |
| 171 | bytes_to_skip += varint::Decode(proto_, &value); |
| 172 | bytes_to_skip += value; |
| 173 | break; |
| 174 | |
| 175 | case WireType::kFixed32: |
| 176 | bytes_to_skip = sizeof(uint32_t); |
| 177 | break; |
| 178 | |
| 179 | case WireType::kFixed64: |
| 180 | bytes_to_skip = sizeof(uint64_t); |
| 181 | break; |
| 182 | } |
| 183 | |
| 184 | if (bytes_to_skip == 0) { |
| 185 | state_ = kDecodeFailed; |
| 186 | } else { |
| 187 | proto_ = proto_.subspan(bytes_to_skip); |
| 188 | } |
| 189 | } |
| 190 | |
| 191 | } // namespace pw::protobuf |