JDK14/Java14源码在线阅读

/*
 * Copyright (c) 1997, 2019, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 *
 */

#ifndef CPU_X86_BYTES_X86_HPP
#define CPU_X86_BYTES_X86_HPP

#include "memory/allocation.hpp"
#include "utilities/align.hpp"
#include "utilities/macros.hpp"

class Bytes: AllStatic {
 private:
#ifndef AMD64
  // Helper function for swap_u8
  static inline u8   swap_u8_base(u4 x, u4 y);        // compiler-dependent implementation
#endif // AMD64

 public:
  // Efficient reading and writing of unaligned unsigned data in platform-specific byte ordering
  template <typename T>
  static inline T get_native(const void* p) {
    assert(p != NULL, "null pointer");

    T x;

    if (is_aligned(p, sizeof(T))) {
      x = *(T*)p;
    } else {
      memcpy(&x, p, sizeof(T));
    }

    return x;
  }

  template <typename T>
  static inline void put_native(void* p, T x) {
    assert(p != NULL, "null pointer");

    if (is_aligned(p, sizeof(T))) {
      *(T*)p = x;
    } else {
      memcpy(p, &x, sizeof(T));
    }
  }

  static inline u2   get_native_u2(address p)         { return get_native<u2>((void*)p); }
  static inline u4   get_native_u4(address p)         { return get_native<u4>((void*)p); }
  static inline u8   get_native_u8(address p)         { return get_native<u8>((void*)p); }
  static inline void put_native_u2(address p, u2 x)   { put_native<u2>((void*)p, x); }
  static inline void put_native_u4(address p, u4 x)   { put_native<u4>((void*)p, x); }
  static inline void put_native_u8(address p, u8 x)   { put_native<u8>((void*)p, x); }

  // Efficient reading and writing of unaligned unsigned data in Java
  // byte ordering (i.e. big-endian ordering). Byte-order reversal is
  // needed since x86 CPUs use little-endian format.
  template <typename T>
  static inline T get_Java(const address p) {
    T x = get_native<T>(p);

    if (Endian::is_Java_byte_ordering_different()) {
      x = swap<T>(x);
    }

    return x;
  }

  template <typename T>
  static inline void put_Java(address p, T x) {
    if (Endian::is_Java_byte_ordering_different()) {
      x = swap<T>(x);
    }

    put_native<T>(p, x);
  }

  static inline u2   get_Java_u2(address p)           { return get_Java<u2>(p); }
  static inline u4   get_Java_u4(address p)           { return get_Java<u4>(p); }
  static inline u8   get_Java_u8(address p)           { return get_Java<u8>(p); }

  static inline void put_Java_u2(address p, u2 x)     { put_Java<u2>(p, x); }
  static inline void put_Java_u4(address p, u4 x)     { put_Java<u4>(p, x); }
  static inline void put_Java_u8(address p, u8 x)     { put_Java<u8>(p, x); }

  // Efficient swapping of byte ordering
  template <typename T>
  static T swap(T x) {
    switch (sizeof(T)) {
    case sizeof(u1): return x;
    case sizeof(u2): return swap_u2(x);
    case sizeof(u4): return swap_u4(x);
    case sizeof(u8): return swap_u8(x);
    default:

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