FileSourceProvider.kt

TLDR

The FileSourceProvider class in the shark package is responsible for providing access to a file as both streaming and random access sources.

Methods

openStreamingSource

This method returns a BufferedSource object that allows for streaming read access to the file.

openRandomAccessSource

This method returns a RandomAccessSource object that allows for random access read access to the file. It reads the file in chunks, stores the chunks in an internal buffer, and provides the requested data in a Buffer object.

Classes

FileSourceProvider

This class implements the DualSourceProvider interface and provides access to a file as both streaming and random access sources. It uses Okio to create a BufferedSource object for streaming access and a custom RandomAccessSource implementation for random access.

package shark

import java.io.File
import java.io.RandomAccessFile
import kotlin.math.min
import okio.Buffer
import okio.BufferedSource
import okio.Okio

class FileSourceProvider(private val file: File) : DualSourceProvider {
  override fun openStreamingSource(): BufferedSource = Okio.buffer(Okio.source(file.inputStream()))

  override fun openRandomAccessSource(): RandomAccessSource {

    val randomAccessFile = RandomAccessFile(file, "r")

    val arrayBuffer = ByteArray(500_000)

    return object : RandomAccessSource {
      override fun read(
        sink: Buffer,
        position: Long,
        byteCount: Long
      ): Long {
        val byteCountInt = byteCount.toInt()
        randomAccessFile.seek(position)
        var totalBytesRead = 0
        val maxRead = arrayBuffer.size
        while (totalBytesRead < byteCount) {
          val toRead = min(byteCountInt - totalBytesRead, maxRead)
          val bytesRead = randomAccessFile.read(arrayBuffer, 0, toRead)
          if (bytesRead == -1) {
            check(totalBytesRead != 0) {
              "Did not expect to reach end of file after reading 0 bytes"
            }
            break
          }
          sink.write(arrayBuffer, 0, bytesRead)
          totalBytesRead += bytesRead
        }
        return totalBytesRead.toLong()
      }

      override fun close() {
        try {
          randomAccessFile.close()
        } catch (ignored: Throwable) {
          SharkLog.d(ignored) { "Failed to close file, ignoring" }
        }
      }
    }
  }
}