DouKaku?

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

typedef unsigned short utf16char; /* sizeof(short) >= 2 octets */
#define UTF8_MAXOCTETS 3 /* UCS-2ではutf-8にしたとき3 octets以内に収まる */
typedef struct{                                                           
        int len;                                                          
        char data[UTF8_MAXOCTETS];                                        
} Utf8char;                                                               

void encode(Utf8char *utf8, utf16char utf16){
        int i, len;                          

        if(!(utf16 & (~0x7f))) len = 1;
        else if(!(utf16 & (~0x7ff))) len = 2;
        else len = 3;                        

        switch(len){
        case 1:     
                utf8->data[0] = utf16 & 0x7f;
                break;                       
        case 2:                              
                utf8->data[0] = (utf16>>6 & 0x1f) | 0xc0;
                utf8->data[1] = (utf16 & 0x3f) | 0x80;   
                break;                                   
        case 3:                                          
                utf8->data[0] = (utf16>>12 & 0xf) | 0xe0;
                utf8->data[1] = (utf16>>6 & 0x3f) | 0x80;
                utf8->data[2] = (utf16 & 0x3f) | 0x80;   
                break;                                   
        }                                                
        utf8->len = len;                                 
}                                                        

void print_bin(char c){
        printf("%d%d%d%d%d%d%d%d ", c>>7&1, c>>6&1, c>>5&1, c>>4&1, c>>3&1, c>>2&1, c>>1&1, c&1);
}                                                                                                

int main(int argc, char **argv){
        int bytes = argc-1, len = bytes / 2;
        int i, j;
        utf16char *utf16;
        char *utf8;
        int u8len = 0;
        Utf8char u8char;

        if(!bytes) return 0;
        if(bytes % 2){
                printf("Invalid input.\n");
                return 1;
        }
        utf16 = malloc(sizeof(utf16char)*len);
        utf8 = malloc(len*UTF8_MAXOCTETS);

        for(i=0,j=1;i<len;i++,j+=2) utf16[i] = strtol(argv[j], NULL, 16)<<8 | strtol(argv[j+1], NULL, 16);

        for(i=0;i<len;i++){
                encode(&u8char, utf16[i]);
                memcpy(utf8 + u8len, u8char.data, u8char.len);
                u8len += u8char.len;
        }
        for(i=0;i<u8len;i++) print_bin(utf8[i]);
        putchar('\n');

        free(utf16);
        free(utf8);
}