AndroidExtensions.kt

TLDR

The AndroidExtensions.kt file in the shark package provides two extension properties for HeapInstance objects. The identityHashCode property returns the system identity hash code of the HeapInstance, while the hexIdentityHashCode property returns the system identity hash code represented as a hexadecimal string.

Methods

N/A

Classes

N/A

package shark

import shark.HeapObject.HeapInstance

/**
 * The system identity hash code, or null if it couldn't be found.
 *
 * Based on the Object.identityHashCode implementation in AOSP.
 *
 * Backing field shadow$_monitor_ was added in API 24.
 * https://cs.android.com/android/_/android/platform/libcore/+
 * /de626ec8a109ea18283d96c720cc57e2f32f67fa:ojluni/src/main/java/java/lang/Object.java;
 * dlc=ba7cc9f5357c323a1006119a20ce025fd4c57fd2
 */
val HeapInstance.identityHashCode: Int?
  get() {
    // Top 2 bits.
    val lockWordStateMask = -0x40000000
    // Top 2 bits are value 2 (kStateHash).
    val lockWordStateHash = -0x80000000
    // Low 28 bits.
    val lockWordHashMask = 0x0FFFFFFF
    val lockWord = this["java.lang.Object", "shadow\$_monitor_"]?.value?.asInt
    return if (lockWord != null && lockWord and lockWordStateMask == lockWordStateHash) {
      lockWord and lockWordHashMask
    } else null
  }

/**
 * The system identity hashCode represented as hex, or null if it couldn't be found.
 * This is the string identifier you see when calling Object.toString() at runtime on a class that
 * does not override its hashCode() method, e.g. com.example.MyThing@6bd57cf
 */
val HeapInstance.hexIdentityHashCode: String?
  get() {
    val hashCode = identityHashCode ?: return null
    return Integer.toHexString(hashCode)
  }