base64.h

#ifndef _BASE64_H_  
#define _BASE64_H_  

#include <stdio.h>   
#include <stdlib.h>  
#include <string.h>  

const char base[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
char* base64_encode(const char* data, int data_len);
char *base64_decode(const char* data, int data_len);
static char find_pos(char ch);

/* */
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 *)skynet_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;

}
/* */
static char find_pos(char ch)
{
	char *ptr = (char*)strrchr(base, ch);//the last position (the only) in base[]   
	return (ptr - base);
}
/* */
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;
	char need[3];
	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 *)skynet_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;
		memset(need, 0, 4);
		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;
}

#endif