[foreign-memaccess+abi] RFR: 8291639: Improve the ability to visualize a MemorySegment in human readable forms [v17]
Gavin Ray
duke at openjdk.org
Mon Sep 5 18:16:58 UTC 2022
On Mon, 5 Sep 2022 14:16:09 GMT, Per Minborg <duke at openjdk.org> wrote:
>> This PR improves the ability to visualize a `MemorySegment` in human-readable forms (`ByteBuffer`, `byte[]` or any other memory abstraction can be viewed by means of wrapping).
>>
>> It exposes a new method via the new utility class `MemoryInspection`
>>
>>
>> /**
>> * Returns a human-readable view of the provided {@code memory} abstraction by optionally
>> * (if not a {@link MemorySession} and {@link Adapter#ofMemorySegment()} already) copying the contents
>> * to a fresh MemorySegment and then view the resulting MemorySegment through the provided {@code layout}.
>> * <p>
>> * Lines are separated with the system-dependent line separator {@link System#lineSeparator() }.
>> * Otherwise, the exact format of the returned view is unspecified and should not
>> * be acted upon programmatically.
>> * <p>
>> * As an example, a MemorySegment viewed though the following memory layout
>> * {@snippet lang = java:
>> * var layout = MemoryLayout.structLayout(
>> * ValueLayout.JAVA_INT.withName("x"),
>> * ValueLayout.JAVA_INT.withName("y")
>> * ).withName("Point");
>> *}
>> * might be rendered to something like this:
>> * {@snippet lang = text:
>> * Point {
>> * x=1,
>> * y=2
>> * }
>> *}
>> * <p>
>> * This method is intended to view memory abstractions through small and medium-sized memory layouts.
>> *
>> * @param memory to be viewed
>> * @param adapter to apply to the provided memory to determine the size and content of the memory abstraction.
>> * @param layout to use as a layout when viewing the memory segment
>> * @param renderer to apply when rendering value layouts
>> * @param <M> the memory abstraction type.
>> * @return a view of the memory abstraction viewed through the memory layout
>> * @throws OutOfMemoryError if the view exceeds the array size VM limit
>> */
>> public static <M> String toString(M memory,
>> Adapter<M> adapter,
>> MemoryLayout layout,
>> ValueLayoutRenderer renderer) {
>>
>>
>>
>> the existing `HexFormat` class will also get a new configurable `MemoryDumper` that can produce dumps of MemorySegments, byte arrays and ByteBuffers:
>>
>>
>> 0000000000000000 54 68 65 20 71 75 69 63 6B 20 62 72 6F 77 6E 20 |The quick brown |
>> 0000000000000010 66 6F 78 20 6A 75 6D 70 65 64 20 6F 76 65 72 20 |fox jumped over |
>> 0000000000000020 74 68 65 20 6C 61 7A 79 20 64 6F 67 0A 53 65 63 |the lazy dog.Sec|
>> 0000000000000030 6F 6E 64 20 6C 69 6E 65 09 3A 68 65 72 65 00 00 |ond line.:here..|
>> 0000000000000040 00 00 00 00 |.... |
>>
>>
>> A MemoryDumper can contain any number of columns (either index or data) which can be formatted in a large number of ways using composable `HexFormat` instances. Even more configuration possibilities can be achieved by providing custom formatting lambdas.
>
> Per Minborg has updated the pull request incrementally with one additional commit since the last revision:
>
> Update MemoryInspection JavaDoc
src/java.base/share/classes/java/lang/foreign/MemoryInspection.java line 187:
> 185: * @return rendered String
> 186: */
> 187: default String render(ValueLayout.OfAddress addressLayout, MemorySegment value) {
I think you can make it take `Addressable` so it works for both `MemorySegment` and `MemoryAddress`:
default String render(ValueLayout.OfAddress addressLayout, Addressable value) {
requireNonNull(addressLayout);
return String.format("0x%0" + (ValueLayout.ADDRESS.byteSize() * 2) + "X", value.address());
}
In JDK 20 release I get an error:
Trying to do `(MemorySegment)` cast fails:
But if I make it take `Addressable` instead, then it works:
-------------
PR: https://git.openjdk.org/panama-foreign/pull/695
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