c base64加解密

#include "stdafx.h"

#include "Base64.h"

#include <stdio.h>

const char base[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";

int main(int argc, char* argv[])

{

char *t = "那个abcd你好吗，哈哈，ANMOL";

int i = 0;

int j = strlen(t);

char *enc = base64_encode(t, j);

int len = strlen(enc);

char *dec = base64_decode(enc, len);

printf("\noriginal: %s\n", t);

printf("\nencoded : %s\n", enc);

printf("\ndecoded : %s\n", dec);

free(enc);

free(dec);

return 0;

}

/* Base64 编码 */

char *base64_encode(const char* data, int data_len)

{

//int data_len = strlen(data);

int prepare = 0;

int ret_len;

int temp = 0;

char *ret = NULL;

char *f = NULL;

int tmp = 0;

char changed[4];

int i = 0;

ret_len = data_len / 3;

temp = data_len % 3;

if (temp > 0)

{

ret_len += 1;

}

ret_len = ret_len*4 + 1;

ret = (char *)malloc(ret_len);

if ( ret == NULL)

{

printf("No enough memory.\n");

exit(0);

}

memset(ret, 0, ret_len);

f = ret;

while (tmp < data_len)

{

temp = 0;

prepare = 0;

memset(changed, '\0', 4);

while (temp < 3)

{

//printf("tmp = %d\n", tmp);

if (tmp >= data_len)

{

break;

}

prepare = ((prepare << 8) | (data[tmp] & 0xFF));

tmp++;

temp++;

}

prepare = (prepare<<((3-temp)*8));

//printf("before for : temp = %d, prepare = %d\n", temp, prepare);

for (i = 0; i < 4 ;i++ )

{

if (temp < i)

{

changed[i] = 0x40;

}

else

{

changed[i] = (prepare>>((3-i)*6)) & 0x3F;

}

*f = base[changed[i]];

//printf("%.2X", changed[i]);

f++;

}

}

*f = '\0';

return ret;

}

/* 转换算子 */

static char find_pos(char ch)

{

char *ptr = (char*)strrchr(base, ch);//the last position (the only) in base[]

return (ptr - base);

}

/* Base64 解码 */

char *base64_decode(const char *data, int data_len)

{

int ret_len = (data_len / 4) * 3;

int equal_count = 0;

char *ret = NULL;

char *f = NULL;

int tmp = 0;

int temp = 0;

int prepare = 0;

int i = 0;

if (*(data + data_len - 1) == '=')

{

equal_count += 1;

}

if (*(data + data_len - 2) == '=')

{

equal_count += 1;

}

if (*(data + data_len - 3) == '=')

{//seems impossible

equal_count += 1;

}

switch (equal_count)

{

case 0:

ret_len += 4;//3 + 1 [1 for NULL]

break;

case 1:

ret_len += 4;//Ceil((6*3)/8)+1

break;

case 2:

ret_len += 3;//Ceil((6*2)/8)+1

break;

case 3:

ret_len += 2;//Ceil((6*1)/8)+1

break;

}

ret = (char *)malloc(ret_len);

if (ret == NULL)

{

printf("No enough memory.\n");

exit(0);

}

memset(ret, 0, ret_len);

f = ret;

while (tmp < (data_len - equal_count))

{

temp = 0;

prepare = 0;

while (temp < 4)

{

if (tmp >= (data_len - equal_count))

{

break;

}

prepare = (prepare << 6) | (find_pos(data[tmp]));

temp++;

tmp++;

}

prepare = prepare << ((4-temp) * 6);

for (i=0; i<3 ;i++ )

{

if (i == temp)

{

break;

}

*f = (char)((prepare>>((2-i)*8)) & 0xFF);

f++;

}

}

*f = '\0';

return ret;

}