platform/platform-impl/src/com/intellij/openapi/components/impl/stores/StreamProvider.java

package com.intellij.openapi.components.impl.stores;

import com.intellij.openapi.components.RoamingType;
import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;

import java.io.IOException;
import java.io.InputStream;
import java.util.Collection;
import java.util.Collections;

public abstract class StreamProvider {
  public static final StreamProvider[] EMPTY_ARRAY = new StreamProvider[0];

  public boolean isEnabled() {
    return true;
  }

  /**
   * If true, special version file per storage file will keep version of component.
   * On load remote data will be ignored if local version of component is higher.
   * If your storage is always in connected state (for example, git provides you local working copy), you don't need it.
   */
  public boolean isVersioningRequired() {
    return false;
  }

  /**
   * fileSpec Only main fileSpec, not version
   */
  public boolean isApplicable(@NotNull String fileSpec, @NotNull RoamingType roamingType) {
    return true;
  }

  /**
   * @param fileSpec
   * @param content bytes of content, size of array is not actual size of data, you must use {@code size}
   * @param size actual size of data
   * @param roamingType
   * @param async
   */
  public abstract void saveContent(@NotNull String fileSpec, @NotNull byte[] content, int size, @NotNull RoamingType roamingType, boolean async) throws IOException;

  @Nullable
  public abstract InputStream loadContent(@NotNull String fileSpec, @NotNull RoamingType roamingType) throws IOException;

  @NotNull
  public Collection<String> listSubFiles(@NotNull String fileSpec, @NotNull RoamingType roamingType) {
    return Collections.emptyList();
  }

  /**
   * Delete file or directory
   */
  public abstract void delete(@NotNull String fileSpec, @NotNull RoamingType roamingType);
}