rot1fs.fist

来自「Solaris操作系统下的过滤驱动程序, C源码程序.」· FIST 代码 · 共 57 行

%{

  /*
   * rot1fs: shift each byte by one, which is better
   * than rot13 in that every byte is changed, and double-encoding is not
   * like decoding (as with rot13).
   */

%}
filter data;
encoding_blocksize 1;
encoding_type block;
debug on;
%%
%%


/*
 * add 1 to each byte
 * return the number of bytes written
 */
int
rot1fs_encode_block(const char *inbuf, char *outbuf, int len, const vnode_t *vp, const vfs_t *vfsp, u_long pagenum)
{
    unsigned char *incp = (unsigned char *) inbuf;
    unsigned char *outcp = (unsigned char *) outbuf;
    int i;

    for (i = 0; i < len; i++, incp++, outcp++)
	*outcp = *incp + 1;
    return len;
}


/*
 * subtract 1 from each byte
 * return the number of bytes written
 */
int
rot1fs_decode_block(const char *inbuf, char *outbuf, int len, const vnode_t *vp, const vfs_t *vfsp, u_long pagenum)
{
    unsigned char *incp = (unsigned char *) inbuf;
    unsigned char *outcp = (unsigned char *) outbuf;
    int i;

    for (i = 0; i < len; i++, incp++, outcp++)
	*outcp = *incp - 1;
    return len;
}


/*
 * Local variables:
 * c-basic-offset: 4
 * End:
 */