Cのリハビリ

gistfile1.c

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

void encode(char *target, char *str) {
        
        char *result = malloc(strlen(target) * 8 + 1);
        
        if(result) {
                
                int b, sum;
                
                for(sum = 0; *target; *target++)
                        for(b = 1; b <= 128; b <<= 1)
                                result[sum++] = str[*target & b ? 1 : 0];
                
                result[sum] = 0;
                printf("%s", result);
                free(result);
        }
}

void decode(char *target, char *str) {
        
        int l = strlen(target);
        
        if(l & 7)
                return;
        
        int sum = l >> 3;
        char *result = malloc(sum + 1);

        if(result) {
                
                int i, j, b;
                
                for(j = 0; j < sum; j++){
                        for(i = 7, b = 0; i >= 0; i--)
                                if(target[i] - str[0])
                                        b |= (1 << i);
                        
                        target += 8;
                        result[j] = b;
                }
                
                result[sum] = 0;
                printf("%s", result);
                free(result);
                
        }
        
}

int main(int argc, char *argv[]) {
        
        int sum = 0;
        
        if(argc > 3) {
                if(*argv[1] == '-' && strlen(argv[3]) == 2) {
                        switch(argv[1][1]) {
                                case 'e':
                                        encode(argv[2], argv[3]);
                                        break;
                                case 'd':
                                        decode(argv[2], argv[3]);
                                        break;
                        }
                }
        }
        
        return 0;
}