From 57a54f824c460d224ab451893863df0fddda5111 Mon Sep 17 00:00:00 2001
From: Jef Driesen <jefdriesen@users.sourceforge.net>
Date: Mon, 28 Dec 2015 14:24:40 +0100
Subject: [PATCH] Add helper functions for converting hexadecimal data.

---
 examples/common.c | 36 ++++++++++++++++++++++++++++++++++++
 examples/common.h |  3 +++
 2 files changed, 39 insertions(+)

diff --git a/examples/common.c b/examples/common.c
index ee552cd..fb7f73e 100644
--- a/examples/common.c
+++ b/examples/common.c
@@ -232,6 +232,42 @@ dctool_descriptor_search (dc_descriptor_t **out, const char *name, dc_family_t f
 	return DC_STATUS_SUCCESS;
 }
 
+static unsigned char
+hex2dec (unsigned char value)
+{
+	if (value >= '0' && value <= '9')
+		return value - '0';
+	else if (value >= 'A' && value <= 'F')
+		return value - 'A' + 10;
+	else if (value >= 'a' && value <= 'f')
+		return value - 'a' + 10;
+	else
+		return 0;
+}
+
+dc_buffer_t *
+dctool_convert_hex2bin (const char *str)
+{
+	// Get the length of the fingerprint data.
+	size_t nbytes = (str ? strlen (str) / 2 : 0);
+	if (nbytes == 0)
+		return NULL;
+
+	// Allocate a memory buffer.
+	dc_buffer_t *buffer = dc_buffer_new (nbytes);
+
+	// Convert the hexadecimal string.
+	for (unsigned int i = 0; i < nbytes; ++i) {
+		unsigned char msn = hex2dec (str[i * 2 + 0]);
+		unsigned char lsn = hex2dec (str[i * 2 + 1]);
+		unsigned char byte = (msn << 4) + lsn;
+
+		dc_buffer_append (buffer, &byte, 1);
+	}
+
+	return buffer;
+}
+
 void
 dctool_file_write (const char *filename, dc_buffer_t *buffer)
 {
diff --git a/examples/common.h b/examples/common.h
index 55dbb91..f17d578 100644
--- a/examples/common.h
+++ b/examples/common.h
@@ -45,6 +45,9 @@ dctool_event_cb (dc_device_t *device, dc_event_type_t event, const void *data, v
 dc_status_t
 dctool_descriptor_search (dc_descriptor_t **out, const char *name, dc_family_t family, unsigned int model);
 
+dc_buffer_t *
+dctool_convert_hex2bin (const char *str);
+
 void
 dctool_file_write (const char *filename, dc_buffer_t *buffer);