EPQ_totp_lock/base32.c

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C
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2024-12-09 23:20:24 +08:00
#include <ctype.h>
const char base32_map[33] = "ABCDEFGHJKLMNPQRSTUVWXYZ23456789";
/**
No type safety
*/
#define MAX(a, b) ((a) > (b) ? (a) : (b))
#define MIN(a, b) ((a) < (b) ? (a) : (b))
/**
return sym value or -1 if not found
*/
static int decode_sym(int sym) {
int i;
for (i = 0; i < 32; i++) {
if (sym == base32_map[i]) {
return i;
}
}
return -1;
}
int base32_encode(char *dest, int destlen_chars, const void *srcbits,
int srclen_bits) {
const unsigned char *src = srcbits;
int dstlen_need = (srclen_bits + 4) / 5 + 1, i, didx = 0;
*dest = 0;
if (destlen_chars < dstlen_need) {
return 0;
}
for (i = 0; i < srclen_bits; i += 5) {
int sym, sidx = i / 8, bit_offs = i % 8;
if (bit_offs <= 3) {
sym = src[sidx] >> (3 - bit_offs);
} else {
sym = src[sidx] << (bit_offs - 3);
if (i + 1 < srclen_bits) {
sym |= src[sidx + 1] >> (11 - bit_offs);
}
}
sym &= 0x1f;
if (srclen_bits - i < 5) {
sym &= 0x1f << (5 + i - srclen_bits);
}
dest[didx++] = base32_map[sym];
}
for (i = 0; i < (8 - (didx % 8)) % 8; i++) {
dest[didx++] = '=';
}
dest[didx] = '\0';
return 0;
}
int base32_decode(unsigned char *dest, int destlen_bits, const char *src) {
int out_bits = 0;
for (; *src; src++) {
int sym, sbits, dbits, b;
if (isspace(*src) || *src == '-') {
continue;
}
sym = decode_sym(*src);
if (sym < 0) {
return -1;
}
if (out_bits >= destlen_bits) {
break;
}
sbits = MIN(5, destlen_bits - out_bits);
if (sbits < 5) {
sym >>= (5 - sbits);
}
dbits = 8 - (out_bits & 7);
b = MIN(dbits, sbits);
if (dbits == 8) {
dest[out_bits / 8] = 0;
}
dest[out_bits / 8] |= (sym << (dbits - b)) >> (sbits - b);
out_bits += b;
sbits -= b;
if (sbits > 0) {
dest[out_bits / 8] = sym << (8 - sbits);
out_bits += sbits;
}
}
return out_bits;
}