base64.c

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
const char base[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/="; 
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; 

}