Scott James Remnant | a19e285 | 2021-12-14 17:53:04 -0800 | [diff] [blame] | 1 | // Copyright 2021 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_varint/stream.h" |
| 16 | |
| 17 | #include <cstddef> |
| 18 | #include <cstdint> |
| 19 | #include <span> |
| 20 | |
| 21 | #include "pw_status/status_with_size.h" |
| 22 | #include "pw_stream/stream.h" |
| 23 | #include "pw_varint/varint.h" |
| 24 | |
| 25 | namespace pw { |
| 26 | namespace varint { |
| 27 | |
| 28 | StatusWithSize Read(stream::Reader& reader, int64_t* output) { |
| 29 | uint64_t value = 0; |
| 30 | StatusWithSize count = Read(reader, &value); |
| 31 | if (!count.ok()) { |
| 32 | return count; |
| 33 | } |
| 34 | |
| 35 | *output = ZigZagDecode(value); |
| 36 | return count; |
| 37 | } |
| 38 | |
| 39 | StatusWithSize Read(stream::Reader& reader, uint64_t* output) { |
| 40 | uint64_t value = 0; |
| 41 | size_t count = 0; |
| 42 | |
| 43 | while (true) { |
| 44 | if (count >= varint::kMaxVarint64SizeBytes) { |
| 45 | // Varint can't fit a uint64_t. |
| 46 | return StatusWithSize::OutOfRange(); |
| 47 | } |
| 48 | |
| 49 | std::byte b; |
| 50 | if (auto result = reader.Read(std::span(&b, 1)); !result.ok()) { |
| 51 | return StatusWithSize(result.status(), 0); |
| 52 | } |
| 53 | |
| 54 | value |= static_cast<uint64_t>(b & std::byte(0b01111111)) << (7 * count); |
| 55 | ++count; |
| 56 | |
| 57 | // MSB == 0 indicates last byte of the varint. |
| 58 | if ((b & std::byte(0b10000000)) == std::byte(0)) { |
| 59 | break; |
| 60 | } |
| 61 | } |
| 62 | |
| 63 | *output = value; |
| 64 | return StatusWithSize(count); |
| 65 | } |
| 66 | |
| 67 | } // namespace varint |
| 68 | } // namespace pw |