我正在实施DES(与EBC)作为学校工作的一部分。 我正在使用来自<stdbool.h>布尔数组bool[64]作为块。 该阵列每个位使用1个字节(当我尝试使用memcpy for 64bits = 8个字节而不是64个字节时,我学到了很多东西)。 无论如何,如何进入位阵列? 现在,我正在阅读一个未签名的长并转换它。 如下所示:
unsigned long buf; bool I[64], O[64]; int ctr = 0; while((ctr = fread(&buf, 1, 8, fin))>0) { dectobin(buf, I); encrypt(I, O); buf=bintodec(O); fwrite(&buf, 8, 1, fout); buf = 0; }功能是:
void dectobin(unsigned long dec, bool bin[64]) { int i; for(i = 0; i< 64; i++) bin[i] = (dec>>(63-i)) & 1; } unsigned long bintodec(bool bin[64]) { unsigned long dec = 0; int i; for(i = 0; i < 64; i++) { dec <<= 1; dec |= (int)(bin[i]); } return dec; }有一个更好的方法吗?
I am implementing DES (with EBC) as part of school work. I am using boolean arrays bool[64] from <stdbool.h> for the blocks. The array uses 1 byte for each bit (I learned this the hard way when I tried memcpy for 64bits=8 bytes instead of 64 bytes). Anyway, how to fread into the bit array? Right now, I'm reading into an unsigned long and converting it. Like below:
unsigned long buf; bool I[64], O[64]; int ctr = 0; while((ctr = fread(&buf, 1, 8, fin))>0) { dectobin(buf, I); encrypt(I, O); buf=bintodec(O); fwrite(&buf, 8, 1, fout); buf = 0; }The functions are:
void dectobin(unsigned long dec, bool bin[64]) { int i; for(i = 0; i< 64; i++) bin[i] = (dec>>(63-i)) & 1; } unsigned long bintodec(bool bin[64]) { unsigned long dec = 0; int i; for(i = 0; i < 64; i++) { dec <<= 1; dec |= (int)(bin[i]); } return dec; }Is there a better way to do this?
最满意答案
你不能直接在bool数组中找到位 (您必须读取字节并手动分配每个字节的每个8位)。
另一种解决方案,它也消耗更少的内存: 一组8个字符。 可以直接进行fread-ed,并通过二进制或/和&|来访问这些位 如果你有一个char c和0到7之间的位数n: 将c中的位n设置为1:
c |= 1<<n;将c中的位n设置为0:
c &= ~(1<<n);检查c中的位n是否为1:
if(c & (1<<n))You can´t directly fread bits in a bool array (you would have to read bytes and assign each 8 bits of each byte manually).
Another solution, which consumes less memory too: An array of 8 chars. Can be fread-ed directly, and the bits are accessed by binary Or/And & | If you have a char c and a bit number n between 0 and 7: Set bit n in c to 1:
c |= 1<<n;Set bit n in c to 0:
c &= ~(1<<n);Check if bit n in c is 1:
if(c & (1<<n))更多推荐
发布评论