utils/byte_readers.h

// Copyright 2026 Google LLC
//
// 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.
//

#ifndef THIRD_PARTY_CREDENTIO_UTILS_BYTE_READERS_H_
#define THIRD_PARTY_CREDENTIO_UTILS_BYTE_READERS_H_

#include "absl/status/status.h"
#include "absl/status/status_macros.h"
#include "absl/status/statusor.h"
#include "absl/strings/str_format.h"
#include "absl/strings/string_view.h"
#include "riegeli/endian/endian_reading.h"

namespace credentio {

// Reads a big-endian unsigned integer of type `N` from the supplied segment.
// Returns an error if the segment is not large enough to contain the integer.
template <typename N>
absl::StatusOr<N> ReadUint(absl::string_view segment) {
  if (segment.size() < sizeof(N)) {
    return absl::InvalidArgumentError(absl::StrFormat(
        "Segment of length %d is not large enough to contain a %d byte "
        "unsigned integer",
        segment.size(), sizeof(N)));
  }
  return riegeli::ReadBigEndian<N>(segment.data());
}

// Reads a big-endian unsigned integer of type `N` from the supplied segment and
// removes the bytes from the segment. Returns an error if the segment is not
// large enough to contain the integer and does not remove any bytes from the
// segment.
template <typename N>
absl::StatusOr<N> ConsumeUint(absl::string_view* segment) {
  if (segment == nullptr) {
    return absl::InvalidArgumentError("Segment is null");
  }
  ABSL_ASSIGN_OR_RETURN(auto result, ReadUint<N>(*segment));
  segment->remove_prefix(sizeof(N));
  return result;
}

// Skips `sizeof(N)` bytes from the supplied segment. Returns an error if the
// segment is not large enough to contain `sizeof(N)` bytes and does not remove
// any bytes from the segment.
template <typename N>
absl::Status SkipBytes(absl::string_view* segment) {
  if (segment == nullptr) {
    return absl::InvalidArgumentError("Segment is null");
  }
  if (segment->size() < sizeof(N)) {
    return absl::InvalidArgumentError(absl::StrFormat(
        "Segment of length %d is not large enough to skip %d bytes",
        segment->size(), sizeof(N)));
  }
  segment->remove_prefix(sizeof(N));
  return absl::OkStatus();
}

}  // namespace credentio

#endif  // THIRD_PARTY_CREDENTIO_UTILS_BYTE_READERS_H_