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/* Copyright (C) 2017 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
#include <assert.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include "libknot/libknot.h"
#include "contrib/ctype.h"
#include "contrib/tolower.h"
/*!
* \brief Convert HEX char to byte.
* \note Expects valid lowercase letters.
*/
static uint8_t hex_to_num(int c)
{
if (c >= '0' && c <= '9') {
return c - '0';
} else {
return c - 'a' + 10;
}
}
/*!
* \brief Convert string encoded in hex to bytes.
*/
int hex_decode(const char *input, uint8_t **output, size_t *output_size)
{
if (!input || input[0] == '\0' || !output || !output_size) {
return KNOT_EINVAL;
}
// input validation (length and content)
size_t input_size = strlen(input);
if (input_size % 2 != 0) {
return KNOT_EMALF;
}
for (size_t i = 0; i < input_size; i++) {
if (!is_xdigit(input[i])) {
return KNOT_EMALF;
}
}
// output allocation
size_t result_size = input_size / 2;
assert(result_size > 0);
uint8_t *result = malloc(result_size);
if (!result) {
return KNOT_ENOMEM;
}
// conversion
for (size_t i = 0; i < result_size; i++) {
int high_nib = knot_tolower(input[2 * i]);
int low_nib = knot_tolower(input[2 * i + 1]);
result[i] = hex_to_num(high_nib) << 4 | hex_to_num(low_nib);
}
*output = result;
*output_size = result_size;
return KNOT_EOK;
}
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