| // Copyright 2020 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. |
| |
| #include "third_party/private_membership/src/internal/utils.h" |
| |
| #include <string> |
| |
| #include "third_party/shell-encryption/src/status_macros.h" |
| |
| namespace private_membership { |
| namespace rlwe { |
| |
| ::rlwe::StatusOr<std::string> Truncate(absl::string_view in, int bit_length) { |
| if (bit_length < 0 || bit_length > in.size() * 8) { |
| return absl::InvalidArgumentError("Truncation bit length out of bounds."); |
| } |
| if (bit_length == 0) { |
| return std::string(); |
| } |
| int ceiled_byte_length = (bit_length - 1) / 8 + 1; |
| std::string res(in.begin(), in.begin() + ceiled_byte_length); |
| if (int remainder_bit_count = bit_length % 8; remainder_bit_count > 0) { |
| int mask = (1 << remainder_bit_count) - 1; |
| res[res.size() - 1] &= (mask << (8 - remainder_bit_count)); |
| } |
| return res; |
| } |
| |
| ::rlwe::StatusOr<uint32_t> TruncateAsUint32(absl::string_view in, |
| int bit_length) { |
| if (bit_length <= 0 || bit_length > in.size() * 8) { |
| return absl::InvalidArgumentError("Truncation bit length out of bounds."); |
| } |
| if (bit_length > 32) { |
| return absl::InvalidArgumentError("Input bit length larger than 32 bits."); |
| } |
| std::string bytes = std::string(in); |
| bytes.resize(4); |
| uint32_t res = (static_cast<unsigned char>(bytes[0]) << 24) | |
| (static_cast<unsigned char>(bytes[1]) << 16) | |
| (static_cast<unsigned char>(bytes[2]) << 8) | |
| static_cast<unsigned char>(bytes[3]); |
| return res >> (32 - bit_length); |
| } |
| |
| bool IsValid(absl::string_view in, int bit_length) { |
| auto status_or_truncated_bytes = Truncate(in, bit_length); |
| if (!status_or_truncated_bytes.ok()) { |
| return false; |
| } |
| return (status_or_truncated_bytes.value() == in); |
| } |
| |
| } // namespace rlwe |
| } // namespace private_membership |