<div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr">I do something like this in my database WIP, here is some similar code to give an idea:</div><div dir="ltr">===================================================================<br><div><br></div><div><div>sealed interface Span<T> {</div><div>  val value: T</div><div>  fun layout(): MemoryLayout</div><div>}</div><div><br></div><div>@JvmInline value class IntSpan(override val value: Int) : Span<Int> {</div><div>  override fun layout(): MemoryLayout = ValueLayout.JAVA_INT</div><div>}</div><div><br></div><div>@JvmInline value class LongSpan(override val value: Long) : Span<Long> {</div><div>  override fun layout(): MemoryLayout = ValueLayout.JAVA_LONG</div><div>}</div><div><br></div><div>@JvmInline value class StringSpan(override val value: String) : Span<String> {</div><div>  override fun layout(): MemoryLayout = MemoryLayout.sequenceLayout(value.length.toLong(), ValueLayout.JAVA_BYTE)</div><div>}</div><div><br></div><div>// <SNIPPED></div><div><br></div><div>// Convert a MemorySegment to a Span<T> where T is the type of the value stored in the segment</div><div>inline fun <reified T> MemorySegment.toSpan(): Span<T> {</div><div>  return when (T::class) {</div><div>    Int::class -> IntSpan(this.get(ValueLayout.JAVA_INT, 0)) as Span<T></div><div>    Long::class -> LongSpan(this.get(ValueLayout.JAVA_LONG, 0)) as Span<T></div><div>    String::class -> StringSpan(this.asSlice(0, this.byteSize()).getUtf8String(0)) as Span<T></div><div>    Boolean::class -> BooleanSpan(this.get(ValueLayout.JAVA_BOOLEAN, 0)) as Span<T></div><div>    Double::class -> DoubleSpan(this.get(ValueLayout.JAVA_DOUBLE, 0)) as Span<T></div><div>    Float::class -> FloatSpan(this.get(ValueLayout.JAVA_FLOAT, 0)) as Span<T></div><div>    Short::class -> ShortSpan(this.get(ValueLayout.JAVA_SHORT, 0)) as Span<T></div><div>    Byte::class -> ByteSpan(this.get(ValueLayout.JAVA_BYTE, 0)) as Span<T></div><div>    Char::class -> CharSpan(this.get(ValueLayout.JAVA_CHAR, 0)) as Span<T></div><div>    else -> throw IllegalArgumentException("Unsupported type ${T::class}")</div><div>  }</div><div>}</div><div><br></div><div>// Convert a Span<T> to a MemorySegment where T is the type of the value stored in the segment</div><div>fun <T> Span<T>.toSegment(): MemorySegment {</div><div>  val segment = MemorySession.global().allocate(this.layout())</div><div>  when (this) {</div><div>    is IntSpan -> segment.set(ValueLayout.JAVA_INT, 0, this.value)</div><div>    is LongSpan -> segment.set(ValueLayout.JAVA_LONG, 0, this.value)</div><div>    is StringSpan -> segment.asSlice(0, segment.byteSize()).setUtf8String(0, this.value)</div><div>    is BooleanSpan -> segment.set(ValueLayout.JAVA_BOOLEAN, 0, this.value)</div><div>    is DoubleSpan -> segment.set(ValueLayout.JAVA_DOUBLE, 0, this.value)</div><div>    is FloatSpan -> segment.set(ValueLayout.JAVA_FLOAT, 0, this.value)</div><div>    is ShortSpan -> segment.set(ValueLayout.JAVA_SHORT, 0, this.value)</div><div>    is ByteSpan -> segment.set(ValueLayout.JAVA_BYTE, 0, this.value)</div><div>    is CharSpan -> segment.set(ValueLayout.JAVA_CHAR, 0, this.value)</div><div>  }</div><div>  return segment</div><div>}</div></div></div></div></div></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Mon, Nov 7, 2022 at 12:34 PM Remi Forax <<a href="mailto:forax@univ-mlv.fr">forax@univ-mlv.fr</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div><div style="font-family:arial,helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><div>It's on my TODO list :)<br></div><div><br></div><div>You create an interface<br></div><div> interface MutableSpan {<br></div><div>   int value();<br></div><div>   void value(int value);</div><div> }<br></div><div><br></div><div>and you can map it to any Panama memory because this is implemented as value class with two fields, a memory segment (or whatever the actual name) and an index.</div><div>Then you need to see a contiguous space of memory as a List of span objects where the value class instances representing the value are created on the fly when asked.</div><div><br></div><div>Rémi<br></div><div><br></div><hr id="m_89570153906364520zwchr"><div><blockquote style="border-left:2px solid rgb(16,16,255);margin-left:5px;padding-left:5px;color:rgb(0,0,0);font-weight:normal;font-style:normal;text-decoration:none;font-family:Helvetica,Arial,sans-serif;font-size:12pt"><b>From: </b>"Red IO" <<a href="mailto:redio.development@gmail.com" target="_blank">redio.development@gmail.com</a>><br><b>To: </b>"panama-dev" <<a href="mailto:panama-dev@openjdk.org" target="_blank">panama-dev@openjdk.org</a>><br><b>Sent: </b>Monday, November 7, 2022 5:59:28 PM<br><b>Subject: </b>Feasibility of a Span class in java<br></blockquote></div><div><blockquote style="border-left:2px solid rgb(16,16,255);margin-left:5px;padding-left:5px;color:rgb(0,0,0);font-weight:normal;font-style:normal;text-decoration:none;font-family:Helvetica,Arial,sans-serif;font-size:12pt"><div dir="auto">Following the development and plans for both Panama's memory access api and the required changes provided by Valhalla while looking at c#'s directions for the last few years I was wondering if writing a class that serves as a universal and easy-to-use interface for accessing memory of all sorts of "value based" types inspired by c#' s Span struct would be beneficial for Java. Of course this assumes the completion of the memory api (panama) , the generic unification (Valhalla) and custom value based types (Valhalla). The idea is to speed up array and string manipulation by using short lived slicing objects (Span). I already wrote a poorly implemented slicer for strings and saw incredible performance gains in comon operations like substring and split. </div><br></blockquote></div></div></div></blockquote></div>