ZipFileSystemSketch.kt

/*
 * Copyright (C) 2021 Square, Inc.
 *
 * 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.
 */
package okio

import java.util.zip.InflaterInputStream
import okio.Path.Companion.toPath

@ExperimentalFileSystem
class ZipFileSystemSketch private constructor(
  private val fileSystem: FileSystem,
  private val zipPath: Path,
  private val entries: List<Entry>
) : FileSystem() {
  
  override fun canonicalize(path: Path): Path {
    return "/".toPath() / path
  }

  override fun metadataOrNull(path: Path): FileMetadata? {
    val canonicalPath = canonicalize(path)
    return entries.firstOrNull { it.path == canonicalPath }?.metadata
  }

  override fun list(dir: Path): List<Path> {
    val canonicalDir = canonicalize(dir)
    return entries.mapNotNull { if (it.path.parent == canonicalDir) it.path else null }
  }

  override fun source(file: Path): Source {
    val canonicalPath = canonicalize(file)
    val entry = entries.firstOrNull { it.path == canonicalPath } 
      ?: throw FileNotFoundException("no such file: $file")
    val zipSource = fileSystem.source(zipPath)
    val cursor = zipSource.cursor ?: throw IOException("zip file not random access")
    cursor.seek(entry.offset)
    // TODO(jwilson): there's some framing needed here.
    return InflaterInputStream(zipSource.buffer().inputStream()).source()
  }

  override fun sink(file: Path): Sink = throw IOException("zip file systems are read-only")

  override fun appendingSink(file: Path): Sink =
    throw IOException("zip file systems are read-only")

  override fun createDirectory(dir: Path): Unit =
    throw IOException("zip file systems are read-only")

  override fun atomicMove(source: Path, target: Path): Unit =
    throw IOException("zip file systems are read-only")

  override fun delete(path: Path): Unit = throw IOException("zip file systems are read-only")

  private class Entry(
    val path: Path,
    val metadata: FileMetadata,
    val offset: Long
  )
}