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-rw-r--r--src/utils/common/hex.c82
1 files changed, 82 insertions, 0 deletions
diff --git a/src/utils/common/hex.c b/src/utils/common/hex.c
new file mode 100644
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--- /dev/null
+++ b/src/utils/common/hex.c
@@ -0,0 +1,82 @@
+/* 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 <http://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;
+}