rolror.cpp

来自「Thinking_in_C___2.rar」· C++ 代码 · 共 29 行

//: C03:Rolror.cpp {O}
// From Thinking in C++, 2nd Edition
// at http://www.BruceEckel.com
// (c) Bruce Eckel 1999
// Copyright notice in Copyright.txt
// Perform left and right rotations

unsigned char ROL(unsigned char val) {
  int highbit;
  if(val & 0x80) // 0x80 is the high bit only
    highbit = 1;
  else
    highbit = 0;
  val <<= 1;  // Left shift (bottom bit becomes 0)
  val |= highbit;  // Rotate the high bit onto the bottom
  return val;  // This becomes the function value
}

unsigned char ROR(unsigned char val) {
  int lowbit;
  if(val & 1) // Check the low bit
    lowbit = 1;
  else
    lowbit = 0;
  val >>= 1; // Right shift by one position
  val |= (lowbit << 7); // Rotate the low bit onto the top
  return val;
} ///:~