形参不能传递值给实参，为何？

daschina

问题描述：
函数qq_decipher((unsigned long *) instr, (unsigned long *) key, (unsigned long *) decrypted); 执行之后，decrypted数组的值没有改变，为什么？

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#define DECRYPT 0x00
#define ENCRYPT 0x01
#include <string.h>
#include "stdio.h"
/*****************************************************************************/
void qq_decipher(unsigned long *const v, const unsigned long *const k, unsigned long *const w)
{
        register unsigned long y = ntohl(v[0]), z = ntohl(v[1]), a = ntohl(k[0]), b = ntohl(k[1]), c = ntohl(k[2]), d = ntohl(k[3]), n = 0x10, sum = 0xE3779B90,        // why this ? must be related with n value
            delta = 0x9E3779B9;

        /* sum = delta<<5, in general sum = delta * n */
        while (n-- > 0) {
                z -= ((y << 4) + c) ^ (y + sum) ^ ((y >> 5) + d);
                y -= ((z << 4) + a) ^ (z + sum) ^ ((z >> 5) + b);
                sum -= delta;
        }

        w[0] = htonl(y);
        w[1] = htonl(z);
}                                // qq_decipher

int qq_decrypt(unsigned char *instr, int instrlen, unsigned char *key, unsigned char *outstr, int *outstrlen_ptr)
{
        unsigned char decrypted[8], m[8], *crypt_buff, *crypt_buff_pre_8, *outp;
        int count, context_start, pos_in_byte, padding;

        int decrypt_every_8_byte(void) {
                for (pos_in_byte = 0; pos_in_byte < 8; pos_in_byte++) {
                        if (context_start + pos_in_byte >= instrlen)
                                return 1;
                        decrypted[pos_in_byte] ^= crypt_buff[pos_in_byte];
                }
                qq_decipher((unsigned long *) decrypted, (unsigned long *) key, (unsigned long *) decrypted);

                context_start += 8;
                crypt_buff += 8;
                pos_in_byte = 0;
                return 1;
        }                        // decrypt_every_8_byte

        // at least 16 bytes and %8 == 0
        if ((instrlen % 8) || (instrlen < 16))
                return 0;
        // get information from header
《《这里》》qq_decipher((unsigned long *) instr, (unsigned long *) key, (unsigned long *) decrypted);
        pos_in_byte = decrypted[0] & 0x7;
        count = instrlen - pos_in_byte - 10;        // this is the plaintext length
        // return if outstr buffer is not large enought or error plaintext length
        if (*outstrlen_ptr < count || count < 0)
                return 0;

        memset(m, 0, 8);
        crypt_buff_pre_8 = m;
        *outstrlen_ptr = count;        // everything is ok! set return string length

        crypt_buff = instr + 8;        // address of real data start
        context_start = 8;        // context is at the second 8 byte
        pos_in_byte++;                // start of paddng stuff

        padding = 1;                // at least one in header
        while (padding <= 2) {        // there are 2 byte padding stuff in header
                if (pos_in_byte < 8) {        // bypass the padding stuff, none sense data
                        pos_in_byte++;
                        padding++;
                }
                if (pos_in_byte == 8) {
                        crypt_buff_pre_8 = instr;
                        if (!decrypt_every_8_byte())
                                return 0;
                }
        }                        // while

        outp = outstr;
        while (count != 0) {
                if (pos_in_byte < 8) {
                        *outp = crypt_buff_pre_8[pos_in_byte] ^ decrypted[pos_in_byte];
                        outp++;
                        count--;
                        pos_in_byte++;
                }
                if (pos_in_byte == 8) {
                        crypt_buff_pre_8 = crypt_buff - 8;
                        if (!decrypt_every_8_byte())
                                return 0;
                }
        }                        // while

        for (padding = 1; padding < 8; padding++) {
                if (pos_in_byte < 8) {
                        if (crypt_buff_pre_8[pos_in_byte] ^ decrypted[pos_in_byte])
                                return 0;
                        pos_in_byte++;
                }
                if (pos_in_byte == 8) {
                        crypt_buff_pre_8 = crypt_buff;
                        if (!decrypt_every_8_byte())
                                return 0;
                }
        }                        // for
        return 1;
}                                // qq_decrypt

int qq_crypt(unsigned char flag,
             unsigned char *instr, int instrlen, unsigned char *key, unsigned char *outstr, int *outstrlen_ptr)
{

        return qq_decrypt(instr, instrlen, key, outstr, outstrlen_ptr);

        return 1;                // flag must be DECRYPT or ENCRYPT
}                                // qq_crypt


int main(){
unsigned long v[4]={0x4fb5bfcc,0x959b2ad7,0x29dc3e6b,0xb7e3e3c7};

unsigned long k[4]={0xd7877ef4,0x2e9e2677,0x76941e42,0x3c0f81d6};

unsigned long out[4]={6};
int outstr_len_ptr=16;

printf("%d \n",qq_crypt(DECRYPT,(unsigned char *)v,16,(unsigned char *)k,(unsigned char *)out,&outstr_len_ptr));
printf("OUT=%lx%lx %lx%lx\n",out[0],out[1],out[2],out[3]);
return 0;
}

END OF FILE

问题描述：
函数qq_decipher((unsigned long *) instr, (unsigned long *) key, (unsigned long *) decrypted); 执行之后，decrypted数组的值没有改变，为什么？

hanchao3c

要改变指针的值，要用二级指针。
总之，写在函数中的变量名表示的东西是不会变的
(unsigned long *) decrypted
无论前面是不是指针