bytes_zero.hpp

/*
 * Copyright (c) 1997, 2019, Oracle and/or its affiliates. All rights reserved.
 * Copyright 2007, 2008, 2009 Red Hat, Inc.
 * 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.
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 */

#ifndef CPU_ZERO_BYTES_ZERO_HPP
#define CPU_ZERO_BYTES_ZERO_HPP

#include "memory/allocation.hpp"

typedef union unaligned {
  u4 u;
  u2 us;
  u8 ul;
} __attribute__((packed)) unaligned;

class Bytes: AllStatic {
 public:
  // Efficient reading and writing of unaligned unsigned data in
  // platform-specific byte ordering.
  static inline u2 get_native_u2(address p){
    unaligned *up = (unaligned *) p;
    return up->us;
  }

  static inline u4 get_native_u4(address p) {
    unaligned *up = (unaligned *) p;
    return up->u;
  }

  static inline u8 get_native_u8(address p) {
    unaligned *up = (unaligned *) p;
    return up->ul;
  }

  static inline void put_native_u2(address p, u2 x) {
    unaligned *up = (unaligned *) p;
    up->us = x;
  }

  static inline void put_native_u4(address p, u4 x) {
    unaligned *up = (unaligned *) p;
    up->u = x;
  }

  static inline void put_native_u8(address p, u8 x) {
    unaligned *up = (unaligned *) p;
    up->ul = x;
  }

  // Efficient reading and writing of unaligned unsigned data in Java
  // byte ordering (i.e. big-endian ordering).
#ifdef VM_LITTLE_ENDIAN
  // Byte-order reversal is needed
  static inline u2 get_Java_u2(address p) {
    return (u2(p[0]) << 8) |
           (u2(p[1])     );
  }
  static inline u4 get_Java_u4(address p) {
    return (u4(p[0]) << 24) |
           (u4(p[1]) << 16) |
           (u4(p[2]) <<  8) |
           (u4(p[3])      );
  }
  static inline u8 get_Java_u8(address p) {
    u4 hi, lo;
    hi = (u4(p[0]) << 24) |
         (u4(p[1]) << 16) |
         (u4(p[2]) <<  8) |
         (u4(p[3])      );
    lo = (u4(p[4]) << 24) |
         (u4(p[5]) << 16) |
         (u4(p[6]) <<  8) |
         (u4(p[7])      );
    return u8(lo) | (u8(hi) << 32);
  }

  static inline void put_Java_u2(address p, u2 x) {
    p[0] = x >> 8;
    p[1] = x;
  }
  static inline void put_Java_u4(address p, u4 x) {
    p[0] = x >> 24;
    p[1] = x >> 16;
    p[2] = x >> 8;
    p[3] = x;
  }
  static inline void put_Java_u8(address p, u8 x) {
    u4 hi, lo;
    lo = x;
    hi = x >> 32;
    p[0] = hi >> 24;
    p[1] = hi >> 16;
    p[2] = hi >> 8;
    p[3] = hi;
    p[4] = lo >> 24;
    p[5] = lo >> 16;
    p[6] = lo >> 8;
    p[7] = lo;
  }

  // Efficient swapping of byte ordering
  static inline u2 swap_u2(u2 x);
  static inline u4 swap_u4(u4 x);
  static inline u8 swap_u8(u8 x);
#else
  // No byte-order reversal is needed
  static inline u2 get_Java_u2(address p) {
    return get_native_u2(p);
  }
  static inline u4 get_Java_u4(address p) {
    return get_native_u4(p);
  }
  static inline u8 get_Java_u8(address p) {
    return get_native_u8(p);
  }

  static inline void put_Java_u2(address p, u2 x) {
    put_native_u2(p, x);
  }
  static inline void put_Java_u4(address p, u4 x) {
    put_native_u4(p, x);
  }
  static inline void put_Java_u8(address p, u8 x) {
    put_native_u8(p, x);
  }

  // No byte-order reversal is needed
  static inline u2 swap_u2(u2 x) { return x; }
  static inline u4 swap_u4(u4 x) { return x; }
  static inline u8 swap_u8(u8 x) { return x; }
#endif // VM_LITTLE_ENDIAN
};

#ifdef VM_LITTLE_ENDIAN
// The following header contains the implementations of swap_u2,
// swap_u4, and swap_u8

#include OS_CPU_HEADER(bytes)

#endif // VM_LITTLE_ENDIAN

#endif // CPU_ZERO_BYTES_ZERO_HPP