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[求助]有人能看出这是什么算法吗
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发表于:
2009-8-15 02:41
6465
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Encode
static char base64[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
int base64_encode(const void *data, int size, char **str)
{
char *s, *p;
int i;
int c;
const unsigned char *q;
p = s = (char*)malloc(size*4/3+4);
if (p == NULL)
return -1;
q = (const unsigned char*)data;
i=0;
for(i = 0; i < size;){
c=q[i++];
c*=256;
if(i < size)
c+=q[i];
i++;
c*=256;
if(i < size)
c+=q[i];
i++;
p[0]=base64[(c&0x00fc0000) >> 18];
p[1]=base64[(c&0x0003f000) >> 12];
p[2]=base64[(c&0x00000fc0) >> 6];
p[3]=base64[(c&0x0000003f) >> 0];
if(i > size)
p[3]='=';
if(i > size+1)
p[2]='=';
p+=4;
}
*p=0;
*str = s;
return strlen(s);
}
char* OnEncode(char *str)
{
int i, len;
char *s, *data;
len = strlen(str) + 1;
s = (char *)malloc(len);
memcpy(s, str, len);
for (i = 0; i < len; i++)
{
s[i] ^= 0x19;
s[i] += 0x86;
}
base64_encode(s, len, &data);
free(s);
return data;
}
Decode
static char base64[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
static int pos(char c)
{
char *p;
for(p = base64; *p; p++)
if(*p == c)
return p - base64;
return -1;
}
int base64_decode(const char *str, char **data)
{
const char *s, *p;
unsigned char *q;
int c;
int x;
int done = 0;
int len;
s = (const char *)malloc(strlen(str));
q = (unsigned char *)s;
for(p=str; *p && !done; p+=4){
x = pos(p[0]);
if(x >= 0)
c = x;
else{
done = 3;
break;
}
c*=64;
x = pos(p[1]);
if(x >= 0)
c += x;
else
return -1;
c*=64;
if(p[2] == '=')
done++;
else{
x = pos(p[2]);
if(x >= 0)
c += x;
else
return -1;
}
c*=64;
if(p[3] == '=')
done++;
else{
if(done)
return -1;
x = pos(p[3]);
if(x >= 0)
c += x;
else
return -1;
}
if(done < 3)
*q++=(c&0x00ff0000)>>16;
if(done < 2)
*q++=(c&0x0000ff00)>>8;
if(done < 1)
*q++=(c&0x000000ff)>>0;
}
len = q - (unsigned char*)(s);
*data = (char*)realloc((void *)s, len);
return len;
}
char* OnDecode(char *str)
{
int i, len;
char *data = NULL;
len = base64_decode(str, &data);
for (i = 0; i < len; i++)
{
data[i] -= 0x86;
data[i] ^= 0x19;
}
return data;
}
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