formats/zip/embedder.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_FORMATS_ZIP_EMBEDDER_H_
#define THIRD_PARTY_CREDENTIO_FORMATS_ZIP_EMBEDDER_H_

#include <cstdint>

#include "absl/base/nullability.h"
#include "absl/status/status.h"
#include "absl/status/statusor.h"
#include "absl/strings/string_view.h"
#include "absl/types/span.h"
#include "formats/zip/reader.h"
#include "riegeli/base/types.h"
#include "riegeli/bytes/reader.h"
#include "riegeli/bytes/writer.h"

namespace credentio {

// A utility class to embed a C2PA manifest store into a ZIP archive.
class ZipEmbedder {
 public:
  struct CopyAndAllocateResult {
    // The offset of the manifest store in the output.
    riegeli::Position manifest_store_offset;
    // The offset of the manifest store's central directory header in the
    // output.
    riegeli::Position manifest_store_central_directory_header_offset;
    // The offset of the central directory in the output.
    riegeli::Position central_directory_offset;
  };

  explicit ZipEmbedder() = default;

  // Copies the file entries from the source to the destination, and allocates
  // space for the manifest store. Returns a `CopyAndAllocateResult` containing
  // the offsets of the manifest store and its central directory header in the
  // output.
  absl::StatusOr<CopyAndAllocateResult> CopyAndAllocate(
      riegeli::Reader* absl_nonnull source,
      absl::Span<const ZipReader::FileEntry> file_entries,
      int64_t manifest_store_size,
      riegeli::Writer* absl_nonnull destination) const;

  // Embeds the manifest store into the ZIP archive at the offsets specified in
  // `copy_and_allocate_result`.
  absl::Status Embed(absl::string_view manifest_store,
                     const CopyAndAllocateResult& copy_and_allocate_result,
                     riegeli::Writer* absl_nonnull destination) const;
};
}  // namespace credentio

#endif  // THIRD_PARTY_CREDENTIO_FORMATS_ZIP_EMBEDDER_H_