jvmMain.okio.SegmentedByteString.kt Maven / Gradle / Ivy

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/*
 * Copyright (C) 2015 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 okio.internal.commonEquals
import okio.internal.commonGetSize
import okio.internal.commonHashCode
import okio.internal.commonInternalGet
import okio.internal.commonRangeEquals
import okio.internal.commonSubstring
import okio.internal.commonToByteArray
import okio.internal.commonWrite
import okio.internal.forEachSegment
import java.io.IOException
import java.io.OutputStream
import java.nio.ByteBuffer
import java.nio.charset.Charset
import java.security.InvalidKeyException
import java.security.MessageDigest
import javax.crypto.Mac
import javax.crypto.spec.SecretKeySpec

/**
 * An immutable byte string composed of segments of byte arrays. This class exists to implement
 * efficient snapshots of buffers. It is implemented as an array of segments, plus a directory in
 * two halves that describes how the segments compose this byte string.
 *
 * The first half of the directory is the cumulative byte count covered by each segment. The
 * element at `directory[0]` contains the number of bytes held in `segments[0]`; the
 * element at `directory[1]` contains the number of bytes held in `segments[0] +
 * segments[1]`, and so on. The element at `directory[segments.length - 1]` contains the total
 * size of this byte string. The first half of the directory is always monotonically increasing.
 *
 * The second half of the directory is the offset in `segments` of the first content byte.
 * Bytes preceding this offset are unused, as are bytes beyond the segment's effective size.
 *
 * Suppose we have a byte string, `[A, B, C, D, E, F, G, H, I, J, K, L, M]` that is stored
 * across three byte arrays: `[x, x, x, x, A, B, C, D, E, x, x, x]`, `[x, F, G]`, and `[H, I, J, K,
 * L, M, x, x, x, x, x, x]`. The three byte arrays would be stored in `segments` in order. Since the
 * arrays contribute 5, 2, and 6 elements respectively, the directory starts with `[5, 7, 13` to
 * hold the cumulative total at each position. Since the offsets into the arrays are 4, 1, and 0
 * respectively, the directory ends with `4, 1, 0]`. Concatenating these two halves, the complete
 * directory is `[5, 7, 13, 4, 1, 0]`.
 *
 * This structure is chosen so that the segment holding a particular offset can be found by
 * binary search. We use one array rather than two for the directory as a micro-optimization.
 */
internal actual class SegmentedByteString internal actual constructor(
  @Transient internal actual val segments: Array,
  @Transient internal actual val directory: IntArray
) : ByteString(EMPTY.data) {

  override fun string(charset: Charset) = toByteString().string(charset)

  override fun base64() = toByteString().base64()

  override fun hex() = toByteString().hex()

  override fun toAsciiLowercase() = toByteString().toAsciiLowercase()

  override fun toAsciiUppercase() = toByteString().toAsciiUppercase()

  override fun digest(algorithm: String): ByteString {
    val digest = MessageDigest.getInstance(algorithm)
    forEachSegment { data, offset, byteCount ->
      digest.update(data, offset, byteCount)
    }
    return ByteString(digest.digest())
  }

  override fun hmac(algorithm: String, key: ByteString): ByteString {
    try {
      val mac = Mac.getInstance(algorithm)
      mac.init(SecretKeySpec(key.toByteArray(), algorithm))
      forEachSegment { data, offset, byteCount ->
        mac.update(data, offset, byteCount)
      }
      return ByteString(mac.doFinal())
    } catch (e: InvalidKeyException) {
      throw IllegalArgumentException(e)
    }
  }

  override fun base64Url() = toByteString().base64Url()

  override fun substring(beginIndex: Int, endIndex: Int): ByteString =
    commonSubstring(beginIndex, endIndex)

  override fun internalGet(pos: Int): Byte = commonInternalGet(pos)

  override fun getSize() = commonGetSize()

  override fun toByteArray(): ByteArray = commonToByteArray()

  override fun asByteBuffer(): ByteBuffer = ByteBuffer.wrap(toByteArray()).asReadOnlyBuffer()

  @Throws(IOException::class)
  override fun write(out: OutputStream) {
    forEachSegment { data, offset, byteCount ->
      out.write(data, offset, byteCount)
    }
  }

  override fun write(buffer: Buffer, offset: Int, byteCount: Int): Unit =
    commonWrite(buffer, offset, byteCount)

  override fun rangeEquals(
    offset: Int,
    other: ByteString,
    otherOffset: Int,
    byteCount: Int
  ): Boolean = commonRangeEquals(offset, other, otherOffset, byteCount)

  override fun rangeEquals(
    offset: Int,
    other: ByteArray,
    otherOffset: Int,
    byteCount: Int
  ): Boolean = commonRangeEquals(offset, other, otherOffset, byteCount)

  override fun indexOf(other: ByteArray, fromIndex: Int) = toByteString().indexOf(other, fromIndex)

  override fun lastIndexOf(other: ByteArray, fromIndex: Int) = toByteString().lastIndexOf(other,
      fromIndex)

  /** Returns a copy as a non-segmented byte string.  */
  private fun toByteString() = ByteString(toByteArray())

  override fun internalArray() = toByteArray()

  override fun equals(other: Any?): Boolean = commonEquals(other)

  override fun hashCode(): Int = commonHashCode()

  override fun toString() = toByteString().toString()

  @Suppress("unused", "PLATFORM_CLASS_MAPPED_TO_KOTLIN") // For Java Serialization.
  private fun writeReplace(): Object = toByteString() as Object
}