Don't recreate attachment InputStream if we don't have to.

core-util-jvm/src/main/java/org/signal/core/util/InputStreamExtensions.kt

@@ -5,9 +5,9 @@
 
 package org.signal.core.util
 
+import java.io.EOFException
 import java.io.IOException
 import java.io.InputStream
-import kotlin.jvm.Throws
 
 /**
  * Reads a 32-bit variable-length integer from the stream.
@@ -80,3 +80,26 @@ fun InputStream.readLength(): Long {
 
   return count
 }
+
+/**
+ * Backported from AOSP API 31 source code.
+ *
+ * @param count number of bytes to skip
+ */
+@Throws(IOException::class)
+fun InputStream.skipNBytesCompat(count: Long) {
+  var n = count
+  while (n > 0) {
+    val ns = skip(n)
+    if (ns in 1..n) {
+      n -= ns
+    } else if (ns == 0L) {
+      if (read() == -1) {
+        throw EOFException()
+      }
+      n--
+    } else {
+      throw IOException("Unable to skip exactly")
+    }
+  }
+}