well_known_headers.h

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// Copyright 2018 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
//
//     http://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 GOOGLE_CLOUD_CPP_GOOGLE_CLOUD_STORAGE_WELL_KNOWN_HEADERS_H
#define GOOGLE_CLOUD_CPP_GOOGLE_CLOUD_STORAGE_WELL_KNOWN_HEADERS_H
 
#include "google/cloud/storage/version.h"
#include "google/cloud/internal/random.h"
#include "google/cloud/optional.h"
#include "absl/types/optional.h"
#include <algorithm>
#include <cstdint>
#include <iostream>
#include <limits>
#include <random>
#include <string>
 
namespace google {
namespace cloud {
namespace storage {
inline namespace STORAGE_CLIENT_NS {
namespace internal {
template <typename H, typename T>
class WellKnownHeader {
 public:
  WellKnownHeader() = default;
  explicit WellKnownHeader(T value) : value_(std::move(value)) {}
 
  char const* header_name() const { return H::header_name(); }
  bool has_value() const { return value_.has_value(); }
  T const& value() const { return value_.value(); }
  template <typename U>
  T value_or(U&& default_val) {
    return value_.value_or(std::forward<U>(default_val));
  }
 
 private:
  absl::optional<T> value_;
};
 
template <typename H, typename T>
std::ostream& operator<<(std::ostream& os, WellKnownHeader<H, T> const& rhs) {
  if (rhs.has_value()) {
    return os << rhs.header_name() << ": " << rhs.value();
  }
  return os << rhs.header_name() << ": <not set>";
}
}  // namespace internal
 
struct ContentType
    : public internal::WellKnownHeader<ContentType, std::string> {
  using WellKnownHeader<ContentType, std::string>::WellKnownHeader;
  static char const* header_name() { return "content-type"; }
};
 
class CustomHeader
    : public internal::WellKnownHeader<CustomHeader, std::string> {
 public:
  CustomHeader() = default;
  explicit CustomHeader(std::string name, std::string value)
      : WellKnownHeader(std::move(value)), name_(std::move(name)) {}
 
  std::string const& custom_header_name() const { return name_; }
 
 private:
  std::string name_;
};
 
std::ostream& operator<<(std::ostream& os, CustomHeader const& rhs);
 
struct IfMatchEtag
    : public internal::WellKnownHeader<IfMatchEtag, std::string> {
  using WellKnownHeader<IfMatchEtag, std::string>::WellKnownHeader;
  static char const* header_name() { return "If-Match"; }
};
 
struct IfNoneMatchEtag
    : public internal::WellKnownHeader<IfNoneMatchEtag, std::string> {
  using WellKnownHeader<IfNoneMatchEtag, std::string>::WellKnownHeader;
  static char const* header_name() { return "If-None-Match"; }
};
 
struct EncryptionKeyData {
  std::string algorithm;
  std::string key;
  std::string sha256;
};
 
EncryptionKeyData EncryptionDataFromBinaryKey(std::string const& key);
 
EncryptionKeyData EncryptionDataFromBase64Key(std::string const& key);
 
struct EncryptionKey
    : public internal::WellKnownHeader<EncryptionKey, EncryptionKeyData> {
  using WellKnownHeader<EncryptionKey, EncryptionKeyData>::WellKnownHeader;
 
  static EncryptionKey FromBinaryKey(std::string const& key);
 
  static EncryptionKey FromBase64Key(std::string const& key);
 
  static char const* prefix() { return "x-goog-encryption-"; }
};
 
std::ostream& operator<<(std::ostream& os, EncryptionKey const& rhs);
 
struct SourceEncryptionKey
    : public internal::WellKnownHeader<SourceEncryptionKey, EncryptionKeyData> {
  using WellKnownHeader<SourceEncryptionKey,
                        EncryptionKeyData>::WellKnownHeader;
 
  static SourceEncryptionKey FromBinaryKey(std::string const& key);
 
  static SourceEncryptionKey FromBase64Key(std::string const& key);
 
  static char const* prefix() { return "x-goog-copy-source-encryption-"; }
};
 
std::ostream& operator<<(std::ostream& os, SourceEncryptionKey const& rhs);
 
template <typename Generator>
EncryptionKeyData CreateKeyFromGenerator(Generator& gen) {
  constexpr int kKeySize = 256 / std::numeric_limits<unsigned char>::digits;
 
  // NOLINTNEXTLINE(readability-identifier-naming)
  constexpr auto minchar = (std::numeric_limits<char>::min)();
  // NOLINTNEXTLINE(readability-identifier-naming)
  constexpr auto maxchar = (std::numeric_limits<char>::max)();
  std::uniform_int_distribution<int> uni(minchar, maxchar);
  std::string key(static_cast<std::size_t>(kKeySize), ' ');
  std::generate_n(key.begin(), key.size(),
                  [&uni, &gen] { return static_cast<char>(uni(gen)); });
  return EncryptionDataFromBinaryKey(key);
}
 
}  // namespace STORAGE_CLIENT_NS
}  // namespace storage
}  // namespace cloud
}  // namespace google
 
#endif  // GOOGLE_CLOUD_CPP_GOOGLE_CLOUD_STORAGE_WELL_KNOWN_HEADERS_H