JDK 一段代码的疑问

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This topic created in 877 days ago, the information mentioned may be changed or developed.

open jdk 17, ByteBuffer 的一段代码

  private ByteBuffer getArray(int index, byte[] dst, int offset, int length) {
        if (
            ((long)length << 0) > Bits.JNI_COPY_TO_ARRAY_THRESHOLD) {
            long bufAddr = address + ((long)index << 0);
            long dstOffset =
                ARRAY_BASE_OFFSET + ((long)offset << 0);
            long len = (long)length << 0;
            try {
                    SCOPED_MEMORY_ACCESS.copyMemory(
                            scope(), null, base(), bufAddr,
                            dst, dstOffset, len);
            } finally {
                Reference.reachabilityFence(this);
            }
        } else {
            int end = offset + length;
            for (int i = offset, j = index; i < end; i++, j++) {
                dst[i] = get(j);
            }
        }
        return this;
    }

我想知道这个左移 0 位目的是什么

7 replies • 2024-01-03 16:58:15 +08:00