common lib: add hex string to bytes conversion

Knot.files

@@ -54,6 +54,8 @@ src/common/hattrie/murmurhash3.c
 src/common/hattrie/murmurhash3.h
 src/common/heap.c
 src/common/heap.h
+src/common/hex.c
+src/common/hex.h
 src/common/latency.c
 src/common/latency.h
 src/common/libtap/tap.c

src/Makefile.am

@@ -232,7 +232,9 @@ libknots_la_SOURCES =				\
 	common/hattrie/hat-trie.c		\
 	common/hattrie/hat-trie.h		\
 	common/hattrie/murmurhash3.c		\
-	common/hattrie/murmurhash3.h
+	common/hattrie/murmurhash3.h		\
+	common/hex.c				\
+	common/hex.h
 
 libknotd_la_SOURCES =				\
 	knot/stat/gatherer.c			\

src/common/hex.c

+/*  Copyright (C) 2011 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 <ctype.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include "common/errcode.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)
+{
+	// input validation (length and content)
+
+	size_t input_size = strlen(input);
+	if (input_size % 2 != 0)
+		return KNOT_EINVAL;
+
+	for (size_t i = 0; i < input_size; i++) {
+		if (!isxdigit(input[i]))
+			return KNOT_EINVAL;
+	}
+
+	// output allocation
+
+	size_t result_size = input_size / 2;
+	uint8_t *result = malloc(result_size * sizeof(uint8_t));
+	if (!output)
+		return KNOT_ENOMEM;
+
+	// conversion
+
+	for (size_t i = 0; i < result_size; i++) {
+		int high_nib = tolower(input[2 * i]);
+		int low_nib  = 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;
+}

src/common/hex.h

+/*  Copyright (C) 2011 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/>.
+*/
+
+/*!
+ * \file hex.h
+ *
+ * \brief Coversion between HEX strings and bytes.
+ *
+ * \author Jan Vcelak <jan.vcelak@nic.cz>
+ *
+ * \addtogroup common_lib
+ * @{
+ */
+
+#ifndef _KNOT_COMMON_HEX_H_
+#define _KNOT_COMMON_HEX_H_
+
+#include <stdint.h>
+#include <stdlib.h>
+
+/*!
+ * \brief Convert string encoded in hex to bytes.
+ *
+ * \param input        Hex encoded input string.
+ * \param output       Decoded bytes.
+ * \param output_size  Size of the output.
+ *
+ * \return Error code, KNOT_EOK if successful.
+ */
+int hex_decode(const char *input, uint8_t **output, size_t *output_size);
+
+#endif // _KNOT_COMMON_HEX_H_
+/*! @} */