DiskCache.java

package com.bumptech.glide.load.engine.cache;

import android.support.annotation.Nullable;
import com.bumptech.glide.load.Key;
import java.io.File;

/**
 * An interface for writing to and reading from a disk cache.
 */
public interface DiskCache {

  /**
   * An interface for lazily creating a disk cache.
   */
  interface Factory {

      /** 250 MB of cache. */
      int DEFAULT_DISK_CACHE_SIZE = 250 * 1024 * 1024;
      String DEFAULT_DISK_CACHE_DIR = "image_manager_disk_cache";

      /**
       * Returns a new disk cache, or {@code null} if no disk cache could be created.
       */
      @Nullable
      DiskCache build();
  }

  /**
   * An interface to actually write data to a key in the disk cache.
   */
  interface Writer {
    /**
     * Writes data to the file and returns true if the write was successful and should be committed,
     * and false if the write should be aborted.
     *
     * @param file The File the Writer should write to.
     */
    boolean write(File file);
  }

  /**
   * Get the cache for the value at the given key.
   *
   * <p> Note - This is potentially dangerous, someone may write a new value to the file at any
   * point in time and we won't know about it. </p>
   *
   * @param key The key in the cache.
   * @return An InputStream representing the data at key at the time get is called.
   */
  @Nullable
  File get(Key key);

  /**
   * Write to a key in the cache. {@link Writer} is used so that the cache implementation can
   * perform actions after the write finishes, like commit (via atomic file rename).
   *
   * @param key    The key to write to.
   * @param writer An interface that will write data given an OutputStream for the key.
   */
  void put(Key key, Writer writer);

  /**
   * Remove the key and value from the cache.
   *
   * @param key The key to remove.
   */
  void delete(Key key);

  /**
   * Clear the cache.
   */
  void clear();
}