C语言位操作源码片段

如下的代码段是关于C语言位操作片段的代码。

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

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    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
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    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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#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;
}