OpenJDK: Implement JVM_CopySwapMemory - #23
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OpenJDK 8u201 added JVM_CopySwapMemory (as part of the OpenJDK 8 backport of JDK-8141491), which copies memory between two regions while swapping the byte order of each element. Without it, the process crashes on the first bulk NIO transfer involving a byte-swapped buffer. The implementation uses a simple byte-reversal loop with byte-wise reads and writes, allowing unaligned source and destination addresses. The copy is overlap-safe: When the ranges overlap, copying proceeds in a direction that prevents unread source bytes from being overwritten. Signed-off-by: Guillermo Rodríguez <grodriguez@ingelabs.com>
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OpenJDK 8u201 added JVM_CopySwapMemory (as part of the OpenJDK 8 backport of JDK-8141491), which copies memory between two regions while swapping the byte order of each element. Without it, the process crashes on the first bulk NIO transfer involving a byte-swapped buffer.
The implementation is a simple byte-reversal loop: alignment-safe (element accesses go through memcpy) and overlap-safe (copying backwards when the destination might lie within the source).