96 lines
3.0 KiB
C
96 lines
3.0 KiB
C
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/*
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* Copyright (C) 2002 Michael Smith <msmith@xiph.org>
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* Copyright (C) 2015-2021 Philipp Schafft <lion@lion.leolix.org>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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#include <stdlib.h>
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#include <string.h>
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#include "base64.h"
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static const signed char base64decode[256] = {
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-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
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-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
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-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, 62, -2, -2, -2, 63,
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52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -2, -2, -2, -1, -2, -2,
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-2, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
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15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -2, -2, -2, -2, -2,
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-2, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
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41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -2, -2, -2, -2, -2,
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-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
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-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
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-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
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-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
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-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
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-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
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-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
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-2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2
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};
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int base64_decode(const char *in, void **out, size_t *len) {
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const unsigned char *input = (const unsigned char *)in;
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size_t todo = strlen(in);
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char *output;
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size_t opp = 0; // output pointer
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if(todo < 4 || (todo % 4) != 0)
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return -1;
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output = calloc(1, todo * 3 / 4 + 5);
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if(!output)
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return -1;
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while(todo) {
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signed char vals[4];
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size_t i;
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for(i = 0; i < (sizeof(vals) / sizeof(*vals)); i++)
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vals[i] = base64decode[*input++];
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if(vals[0] < 0 || vals[1] < 0 || vals[2] < -1 || vals[3] < -1) {
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todo -= 4;
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continue;
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}
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output[opp++] = vals[0] << 2 | vals[1] >> 4;
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/* vals[3] and (if that is) vals[2] can be '=' as padding, which is
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* looked up in the base64decode table as '-1'. Check for this case,
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* and output zero-terminators instead of characters if we've got
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* padding. */
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if(vals[2] >= 0) {
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output[opp++] = ((vals[1] & 0x0F) << 4) | (vals[2] >> 2);
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} else {
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break;
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}
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if(vals[3] >= 0) {
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output[opp++] = ((vals[2] & 0x03) << 6) | (vals[3]);
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} else {
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break;
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}
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todo -= 4;
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}
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output[opp++] = 0;
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*out = output;
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*len = opp - 1;
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return 0;
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}
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