// Copyright 2020 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "src/lib/util/hash.h"

#include "third_party/github.com/google/farmhash/src/farmhash.h"

namespace cobalt::util {

namespace {

const uint32_t kBytesPerInt64 = 8;
const uint32_t kSingleByteMask = 0xFF;

void AppendBytesLittleEndian(uint64_t value, std::string *bytes) {
  for (uint32_t i = 0; i < kBytesPerInt64; i++) {
    bytes->push_back(static_cast<char>((value >> (kBytesPerInt64 * i)) & kSingleByteMask));
  }
}

}  // namespace

std::string FarmhashFingerprint(const std::string &data) {
  farmhash::uint128_t fingerprint = farmhash::Fingerprint128(data);

  std::string bytes;
  AppendBytesLittleEndian(farmhash::Uint128Low64(fingerprint), &bytes);
  AppendBytesLittleEndian(farmhash::Uint128High64(fingerprint), &bytes);

  return bytes;
}

}  // namespace cobalt::util