/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi │
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2021 Justine Alexandra Roberts Tunney │
│ │
│ Permission to use, copy, modify, and/or distribute this software for │
│ any purpose with or without fee is hereby granted, provided that the │
│ above copyright notice and this permission notice appear in all copies. │
│ │
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
│ PERFORMANCE OF THIS SOFTWARE. │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/assert.h"
#include "libc/macros.h"
#include "libc/mem/mem.h"
#include "libc/str/str.h"
const char base32def[] = "0123456789abcdefghjkmnpqrstvwxyz";
int tobits(int b) {
int bits = 0;
while (b && (b >>= 1))
bits++;
return bits;
}
// these functions are based on
// https://github.com/google/google-authenticator-libpam/blob/master/src/base32.c
// Copyright 2010 Google Inc.; Author: Markus Gutschke
// licensed under Apache License, Version 2.0
/**
* Encodes binary to base32 ascii representation.
*
* @param s is input value
* @param sl if -1 implies strlen
* @param a is alphabet string (with power of 2 length)
* @param al is alphabet length (if 0 then Crockford's encoding is used)
* @param ol if non-NULL receives output length
* @return allocated NUL-terminated buffer, or NULL w/ errno
*/
char *EncodeBase32(const char *s, size_t sl, const char *a, size_t al,
size_t *ol) {
size_t count = 0;
char *r = NULL;
if (sl == -1)
sl = s ? strlen(s) : 0;
if (al == 0) {
a = base32def;
al = sizeof(base32def) / sizeof(a[0]);
}
unassert(2 <= al && al <= 128);
int bl = tobits(al);
int mask = (1 << bl) - 1;
size_t n = (sl * 8 + bl - 1) / bl; // calculate output length
if ((r = malloc(n + 1))) {
int buffer = s[0];
size_t next = 1;
int bitsLeft = 8;
while (count < n && (bitsLeft > 0 || next < sl)) {
if (bitsLeft < bl) {
if (next < sl) {
buffer <<= 8;
buffer |= s[next++] & 0xFF;
bitsLeft += 8;
} else {
int pad = bl - bitsLeft;
buffer <<= pad;
bitsLeft += pad;
}
}
bitsLeft -= bl;
r[count++] = a[mask & (buffer >> bitsLeft)];
}
r[count] = '\0';
}
if (ol)
*ol = r ? count : 0;
return r;
}
static signed char kBase32cust[256];
static signed char kBase32[256] = {
-1, -1, -1, -1, -1, -1, -1, -1, -1, -2, -2, -1, -1, -2, -1, -1, // 0x00
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 0x10
-2, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -2, -1, -1, // 0x20
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, -1, -1, -1, -1, -1, -1, // 0x30
-1, 10, 11, 12, 13, 14, 15, 16, 17, 1, 18, 19, 1, 20, 21, -1, // 0x40
22, 23, 24, 25, 26, 0, 27, 28, 29, 30, 31, -1, -1, -1, -1, -1, // 0x50
-1, 10, 11, 12, 13, 14, 15, 16, 17, 1, 18, 19, 1, 20, 21, -1, // 0x60
22, 23, 24, 25, 26, 0, 27, 28, 29, 30, 31, -1, -1, -1, -1, -1, // 0x70
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 0x80
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 0x90
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 0xa0
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 0xb0
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 0xc0
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 0xd0
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 0xe0
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 0xf0
};
/**
* Decodes base32 ascii representation to binary.
*
* This uses Crockford's encoding and skips whitespaces.
* The decoding stops at the first character not in the alphabet.
*
* @param s is input value
* @param sl if -1 implies strlen
* @param a is alphabet string (with power of 2 length)
* @param al is alphabet length (if 0 then Crockford's encoding is used)
* @param ol if non-NULL receives output length
* @return allocated NUL-terminated buffer, or NULL w/ errno
*/
char *DecodeBase32(const char *s, size_t sl, const char *a, size_t al,
size_t *ol) {
size_t count = 0;
char *r = NULL;
if (sl == -1)
sl = s ? strlen(s) : 0;
if (al == 0) {
a = base32def;
al = sizeof(base32def) / sizeof(a[0]);
}
unassert(2 <= al && al <= 128);
int bl = tobits(al);
size_t n = (sl * bl + 1) / 8 + 1; // calculate output length
// process input
if ((r = malloc(n + 1))) {
unsigned int buffer = 0;
signed char *map = kBase32;
int bitsLeft = 0;
if (a != base32def) {
// if the provided alphabet doesn't match the default
map = kBase32cust;
memset(map, -1, 256);
// populate the map based on alphabet
for (int i = 0; i < al; i++)
map[a[i] & 0xff] = i;
}
while (count < n && *s) {
signed char m = map[*s++ & 0xff];
if (m == -2)
continue;
if (m == -1)
break;
buffer <<= bl;
buffer |= m;
bitsLeft += bl;
if (bitsLeft >= 8) {
r[count++] = buffer >> (bitsLeft - 8);
bitsLeft -= 8;
}
}
r[count] = '\0';
}
if (ol)
*ol = r ? count : 0;
return r;
}