-
Notifications
You must be signed in to change notification settings - Fork 0
/
base62.c
131 lines (109 loc) · 3.31 KB
/
base62.c
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
#include <ctype.h>
#include <math.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define DEBUG 0
#define MAX_LEN 8
const char *CHARSET =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
const uint8_t BASE = 62;
const char *FLAG_ENCODE = "-e";
const char *FLAG_DECODE = "-d";
const int8_t OFFSET_ASCII_CHARSET_ALPHA_UC = -65;
const int8_t OFFSET_ASCII_CHARSET_ALPHA_LC = -97 + 26;
const int8_t OFFSET_ASCII_CHARSET_NUMBER = -48 + 26 + 26;
void base62_encode(char *input, uint32_t size, char *encoded);
uint64_t base62_decode(char *input, uint32_t size);
int validate_args(int argc, char **argv);
void print_usage(void);
int main(int argc, char **argv) {
if (validate_args(argc, argv) > 0) {
print_usage();
return EXIT_FAILURE;
}
char *flag = argv[1];
char *input = argv[2];
uint32_t size = strnlen(input, MAX_LEN);
if (DEBUG)
printf("size=%d\n", size);
if (size == 0)
return EXIT_FAILURE;
if (size == MAX_LEN && input[size] != 0)
return EXIT_FAILURE;
if (strncmp(flag, FLAG_ENCODE, 2) == 0) {
char *encoded = malloc((size + 1) * sizeof(char));
base62_encode(input, size, encoded);
printf("%s\n", encoded);
free(encoded);
} else if (strncmp(flag, FLAG_DECODE, 2) == 0) {
uint64_t decoded = base62_decode(input, size);
printf("%llu\n", decoded);
}
return EXIT_SUCCESS;
}
void base62_encode(char *input, uint32_t size, char *encoded) {
if (!input || !encoded)
exit(EXIT_FAILURE);
for (uint32_t i = 0; i < size; i++)
if (!isdigit(input[i]))
exit(EXIT_FAILURE);
uint64_t num = atoll(input);
uint32_t i = 0;
do {
uint8_t r = num % BASE;
num = num / BASE;
if (DEBUG)
printf("%d [%c] %llu\n", r, CHARSET[r], num);
encoded[i] = CHARSET[r];
i += 1;
} while (num);
encoded[i] = 0x00;
uint32_t len = strnlen(encoded, MAX_LEN);
for (uint32_t j = 0; j < len/2; j++) {
char swap = encoded[j];
encoded[j] = encoded[len - j - 1];
encoded[len - j - 1] = swap;
}
}
uint64_t base62_decode(char *input, uint32_t size) {
if (!input)
exit(EXIT_FAILURE);
for (uint32_t i = 0; i < size; i++)
if (!isalnum(input[i]))
exit(EXIT_FAILURE);
uint64_t decoded = 0;
for (uint32_t i = 0; i < size; i++) {
char c = input[i];
uint8_t index = 0;
uint8_t exponent = size - i - 1;
if (isalpha(c)) {
if (islower(c)) {
index = c + OFFSET_ASCII_CHARSET_ALPHA_LC;
} else {
index = c + OFFSET_ASCII_CHARSET_ALPHA_UC;
}
} else {
index = c + OFFSET_ASCII_CHARSET_NUMBER;
}
if (DEBUG)
printf("pow=%d [%c] %d\n", exponent, c, index);
decoded = decoded + (powl(BASE, exponent) * index);
}
return decoded;
}
int validate_args(int argc, char **argv) {
if (argc < 3)
return 1;
char *flag = argv[1];
if (strncmp(flag, FLAG_ENCODE, 2) == 0
|| strncmp(flag, FLAG_DECODE, 2) == 0) {
return 0;
}
return 1;
}
void print_usage(void) {
printf("Usage: <prog> -[e|d] <input_text>\n");
printf("Limitation: works only numbers\n");
}