85 lines
2.6 KiB
C++
85 lines
2.6 KiB
C++
// Copyright 2021 The Pigweed Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License"); you may not
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// use this file except in compliance with the License. You may obtain a copy of
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// the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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// License for the specific language governing permissions and limitations under
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// the License.
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#include "pw_varint/stream.h"
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#include <cstddef>
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#include <cstdint>
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#include "pw_span/span.h"
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#include "pw_status/status_with_size.h"
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#include "pw_stream/stream.h"
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#include "pw_varint/varint.h"
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namespace pw {
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namespace varint {
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StatusWithSize Read(stream::Reader& reader, int64_t* output, size_t max_size) {
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uint64_t value = 0;
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StatusWithSize count = Read(reader, &value, max_size);
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if (!count.ok()) {
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return count;
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}
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*output = ZigZagDecode(value);
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return count;
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}
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StatusWithSize Read(stream::Reader& reader, uint64_t* output, size_t max_size) {
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uint64_t value = 0;
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size_t count = 0;
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while (true) {
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if (count >= varint::kMaxVarint64SizeBytes) {
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// Varint can't fit a uint64_t, this likely means we're reading binary
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// data that is not actually a varint.
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return StatusWithSize::DataLoss();
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}
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if (count >= max_size) {
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// Varint didn't fit within the range given; return OutOfRange() if
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// max_size was 0, but DataLoss if we were reading something we thought
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// was going to be a varint.
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return count > 0 ? StatusWithSize::DataLoss()
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: StatusWithSize::OutOfRange();
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}
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std::byte b;
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if (auto result = reader.Read(span(&b, 1)); !result.ok()) {
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if (count > 0 && result.status().IsOutOfRange()) {
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// Status::OutOfRange on the first byte means we tried to read a varint
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// when we reached the end of file. But after the first byte it means we
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// failed to decode a varint we were in the middle of, and that's not
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// a normal error condition.
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return StatusWithSize(Status::DataLoss(), 0);
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}
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return StatusWithSize(result.status(), 0);
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}
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value |= static_cast<uint64_t>(b & std::byte(0b01111111)) << (7 * count);
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++count;
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// MSB == 0 indicates last byte of the varint.
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if ((b & std::byte(0b10000000)) == std::byte(0)) {
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break;
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}
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}
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*output = value;
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return StatusWithSize(count);
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}
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} // namespace varint
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} // namespace pw
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