C語言位操作源碼片段

如下的代碼段是關于C語言位操作片段的代碼。

  Copyright 2011 Shao-Chuan Wang <shaochuan.wang AT gmail.com>

    Permission is hereby granted, free of charge, to any person obtaining a copy
    of this software and associated documentation files (the "Software"), to deal
    in the Software without restriction, including without limitation the rights
    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
    copies of the Software, and to permit persons to whom the Software is
    furnished to do so, subject to the following conditions:

    The above copyright notice and this permission notice shall be included in
    all copies or substantial portions of the Software.

    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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    THE SOFTWARE.
#include <stdio.h>
#include <stdlib.h>

typedef struct {
  int size;
} packed_bits;

#define INT_MAX_BIT_MASK (1 << (INT_NBITS-1))

{
  if (!b_array)
    return NULL;
  p = malloc(sizeof(packed_bits));
  if (!p) {
    free(b_array);
    return NULL;
  }
  p->size = n_int;
  p->b = b_array;
  return p;
}

{
  int i;
  if (!p)
    return -1;
  b = p->b;
  for (i = p->size-1;i >= 0;i--) {
    b[i] = b[i] << 1;
    if (i-1 >=0 && b[i-1] & INT_MAX_BIT_MASK)
      b[i]++;
  }
  return 0;
}

{
  int i;
  if (!p)
    return -1;
  b = p->b;
  for (i = 0;i < p->size;i++) {
    b[i] = b[i] >> 1;
    if (i+1 < p->size && (b[i+1] & 1))
      b[i] |= INT_MAX_BIT_MASK;
  }
  return 0;  
}

{
  unsigned int offset = n % INT_NBITS;
  unsigned int idx = n / INT_NBITS;
  if (!p)
    return -1;
  b = p->b;
  return (b[idx] & (1 << offset)) != 0;
}

{
  unsigned int offset = n % INT_NBITS;
  unsigned int idx = n / INT_NBITS;
  if (!p)
    return -1;
  b = p->b;
  b[idx] |= (1<<offset);
  return 0;
}

{
  unsigned int offset = n % INT_NBITS;
  unsigned int idx = n / INT_NBITS;
  if (!p)
    return -1;
  b = p->b;
  b[idx] &= ~(1<<offset);

  return 0;
}

{
  int j;
  if (!p)
    return;
  b = p->b;
    printf("%d", read_bit(p, j));
    if (j % INT_NBITS==0)
      printf("n");
  }
  printf("n");
  return;
}

{
  int n_int = 4;
  if (!p) {
    fprintf(stderr, "Out of memory!n");
    return EXIT_FAILURE;
  }

  set_bit(p, 1);
  set_bit(p, 127);
  print_bits(p);

  return 0;
}