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