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