Bluetooth: Host: Remove printk dependency from settings

Some modules use snprintk to format the settings keys. Unfortunately
snprintk is tied with printk which is very large for some embedded
systems.
To be able to have settings enabled without also enabling printk
support, change creation of settings key strings to use bin2hex, strlen
and strcpy instead.
A utility function to make decimal presentation of a byte value is
added as u8_to_dec in lib/os/dec.c
Add new Kconfig setting BT_SETTINGS_USE_PRINTK

Signed-off-by: Kim Sekkelund <ksek@oticon.com>

include/sys/util.h

@@ -170,6 +170,21 @@ size_t bin2hex(const u8_t *buf, size_t buflen, char *hex, size_t hexlen);
  */
 size_t hex2bin(const char *hex, size_t hexlen, u8_t *buf, size_t buflen);
 
+/**
+ * @brief      Convert a u8_t into decimal string representation.
+ *
+ * Convert a u8_t value into ASCII decimal string representation.
+ * The string is terminated if there is enough space in buf.
+ *
+ * @param[out] buf     Address of where to store the string representation.
+ * @param[in]  buflen  Size of the storage area for string representation.
+ * @param[in]  value   The value to convert to decimal string
+ *
+ * @return     The length of the converted string (excluding terminator if
+ *             any), or 0 if an error occurred.
+ */
+u8_t u8_to_dec(char *buf, u8_t buflen, u8_t value);
+
 #endif /* !_ASMLANGUAGE */
 
 /* KB, MB, GB */

lib/os/CMakeLists.txt

@@ -7,6 +7,7 @@ zephyr_sources(
   crc16_sw.c
   crc8_sw.c
   crc7_sw.c
+  dec.c
   fdtable.c
   hex.c
   mempool.c

lib/os/dec.c

@@ -0,0 +1,35 @@
+/*
+ * Copyright (c) 2019 Oticon A/S
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <kernel.h>
+#include <sys/util.h>
+
+u8_t u8_to_dec(char *buf, u8_t buflen, u8_t value)
+{
+	u8_t divisor = 100;
+	u8_t num_digits = 0;
+	u8_t digit;
+
+	while (buflen > 0 && divisor > 0) {
+		digit = value / divisor;
+		if (digit != 0 || divisor == 1 || num_digits != 0) {
+			*buf = (char)digit + '0';
+			buf++;
+			buflen--;
+			num_digits++;
+		}
+
+		value -= digit * divisor;
+		divisor /= 10;
+	}
+
+	if (buflen) {
+		*buf = '\0';
+	}
+
+	return num_digits;
+}
+

subsys/bluetooth/host/Kconfig

@@ -160,7 +160,7 @@ config BT_HOST_CRYPTO
 
 config BT_SETTINGS
 	bool "Store Bluetooth state and configuration persistently"
-	depends on SETTINGS && PRINTK
+	depends on SETTINGS
 	select MPU_ALLOW_FLASH_WRITE if ARM_MPU
 	help
 	  When selected, the Bluetooth stack will take care of storing
@@ -186,6 +186,17 @@ config BT_SETTINGS_CCC_STORE_ON_WRITE
 	  Choosing this option is safer for battery-powered devices or devices
 	  that expect to be reset suddenly. However, it requires additional
 	  workqueue stack space.
+
+config BT_SETTINGS_USE_PRINTK
+	bool "Use snprintk to encode Bluetooth settings key strings"
+	depends on SETTINGS && PRINTK
+	default y
+	help
+	  When selected, Bluetooth settings will use snprintk to encode
+	  key strings.
+	  When not selected, Bluetooth settings will use a faster builtin
+	  function to encode the key string. The drawback is that if
+	  printk is enabled then the program memory footprint will be larger.
 endif # BT_SETTINGS
 
 config BT_WHITELIST

subsys/bluetooth/host/gatt.c

@@ -3412,7 +3412,7 @@ static int bt_gatt_store_cf(struct bt_conn *conn)
 		if (conn->id) {
 			char id_str[4];
 
-			snprintk(id_str, sizeof(id_str), "%u", conn->id);
+			u8_to_dec(id_str, sizeof(id_str), conn->id);
 			bt_settings_encode_key(key, sizeof(key), "cf",
 					       &conn->le.dst, id_str);
 		}
@@ -3538,7 +3538,7 @@ int bt_gatt_store_ccc(u8_t id, const bt_addr_le_t *addr)
 	if (id) {
 		char id_str[4];
 
-		snprintk(id_str, sizeof(id_str), "%u", id);
+		u8_to_dec(id_str, sizeof(id_str), id);
 		bt_settings_encode_key(key, sizeof(key), "ccc",
 				       (bt_addr_le_t *)addr, id_str);
 	} else {
@@ -3609,7 +3609,7 @@ static int bt_gatt_clear_ccc(u8_t id, const bt_addr_le_t *addr)
 	if (id) {
 		char id_str[4];
 
-		snprintk(id_str, sizeof(id_str), "%u", id);
+		u8_to_dec(id_str, sizeof(id_str), id);
 		bt_settings_encode_key(key, sizeof(key), "ccc",
 				       (bt_addr_le_t *)addr, id_str);
 	} else {
@@ -3647,7 +3647,7 @@ static int bt_gatt_clear_cf(u8_t id, const bt_addr_le_t *addr)
 	if (id) {
 		char id_str[4];
 
-		snprintk(id_str, sizeof(id_str), "%u", id);
+		u8_to_dec(id_str, sizeof(id_str), id);
 		bt_settings_encode_key(key, sizeof(key), "cf",
 				       (bt_addr_le_t *)addr, id_str);
 	} else {

subsys/bluetooth/host/keys.c

@@ -216,7 +216,7 @@ void bt_keys_clear(struct bt_keys *keys)
 		if (keys->id) {
 			char id[4];
 
-			snprintk(id, sizeof(id), "%u", keys->id);
+			u8_to_dec(id, sizeof(id), keys->id);
 			bt_settings_encode_key(key, sizeof(key), "keys",
 					       &keys->addr, id);
 		} else {
@@ -258,7 +258,7 @@ int bt_keys_store(struct bt_keys *keys)
 	if (keys->id) {
 		char id[4];
 
-		snprintk(id, sizeof(id), "%u", keys->id);
+		u8_to_dec(id, sizeof(id), keys->id);
 		bt_settings_encode_key(key, sizeof(key), "keys", &keys->addr,
 				       id);
 	} else {

subsys/bluetooth/host/settings.c

@@ -19,6 +19,7 @@
 #include "hci_core.h"
 #include "settings.h"
 
+#if defined(BT_SETTINGS_USE_PRINTK)
 void bt_settings_encode_key(char *path, size_t path_size, const char *subsys,
 			    bt_addr_le_t *addr, const char *key)
 {
@@ -38,12 +39,59 @@ void bt_settings_encode_key(char *path, size_t path_size, const char *subsys,
 
 	BT_DBG("Encoded path %s", log_strdup(path));
 }
+#else
+void bt_settings_encode_key(char *path, size_t path_size, const char *subsys,
+			    bt_addr_le_t *addr, const char *key)
+{
+	size_t len = 3;
+
+	/* Skip if path_size is less than 3; strlen("bt/") */
+	if (len < path_size) {
+		/* Key format:
+		 *  "bt/<subsys>/<addr><type>/<key>", "/<key>" is optional
+		 */
+		strcpy(path, "bt/");
+		strncpy(&path[len], subsys, path_size - len);
+		len = strlen(path);
+		if (len < path_size) {
+			path[len] = '/';
+			len++;
+		}
+
+		for (s8_t i = 5; i >= 0 && len < path_size; i--) {
+			len += bin2hex(&addr->a.val[i], 1, &path[len],
+				       path_size - len);
+		}
+
+		if (len < path_size) {
+			/* Type can be either BT_ADDR_LE_PUBLIC or
+			 * BT_ADDR_LE_RANDOM (value 0 or 1)
+			 */
+			path[len] = '0' + addr->type;
+			len++;
+		}
+
+		if (key && len < path_size) {
+			path[len] = '/';
+			len++;
+			strncpy(&path[len], key, path_size - len);
+			len += strlen(&path[len]);
+		}
+
+		if (len >= path_size) {
+			/* Truncate string */
+			path[path_size - 1] = '\0';
+		}
+	} else if (path_size > 0) {
+		*path = '\0';
+	}
+
+	BT_DBG("Encoded path %s", log_strdup(path));
+}
+#endif
 
 int bt_settings_decode_key(const char *key, bt_addr_le_t *addr)
 {
-	bool high;
-	int i;
-
 	if (settings_name_next(key, NULL) != 13) {
 		return -EINVAL;
 	}
@@ -56,25 +104,8 @@ int bt_settings_decode_key(const char *key, bt_addr_le_t *addr)
 		return -EINVAL;
 	}
 
-	for (i = 5, high = true; i >= 0; key++) {
-		u8_t nibble;
-
-		if (*key >= '0' && *key <= '9') {
-			nibble = *key - '0';
-		} else if (*key >= 'a' && *key <= 'f') {
-			nibble = *key - 'a' + 10;
-		} else {
-			return -EINVAL;
-		}
-
-		if (high) {
-			addr->a.val[i] = nibble << 4;
-			high = false;
-		} else {
-			addr->a.val[i] |= nibble;
-			high = true;
-			i--;
-		}
+	for (u8_t i = 0; i < 6; i++) {
+		hex2bin(&key[i * 2], 2, &addr->a.val[5 - i], 1);
 	}
 
 	BT_DBG("Decoded %s as %s", log_strdup(key), bt_addr_le_str(addr));

tests/lib/sys/util/CMakeLists.txt

@@ -0,0 +1,8 @@
+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.13.1)
+include($ENV{ZEPHYR_BASE}/cmake/app/boilerplate.cmake NO_POLICY_SCOPE)
+project(lib_sys_util_tests)
+
+FILE(GLOB app_sources src/*.c)
+target_sources(app PRIVATE ${app_sources})

tests/lib/sys/util/prj.conf

@@ -0,0 +1 @@
+CONFIG_ZTEST=y

tests/lib/sys/util/src/main.c

@@ -0,0 +1,81 @@
+/*
+ * Copyright (c) 2019 Oticon A/S
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <ztest.h>
+#include <sys/util.h>
+#include <string.h>
+
+/**
+ * @brief Test of u8_to_dec
+ *
+ * This test verifies conversion of various input values.
+ *
+ */
+static void test_u8_to_dec(void)
+{
+	char text[4];
+	u8_t len;
+
+	len = u8_to_dec(text, sizeof(text), 0);
+	zassert_equal(len, 1, "Length of 0 is not 1");
+	zassert_equal(strcmp(text, "0"), 0,
+		      "Value=0 is not converted to \"0\"");
+
+	len = u8_to_dec(text, sizeof(text), 1);
+	zassert_equal(len, 1, "Length of 1 is not 1");
+	zassert_equal(strcmp(text, "1"), 0,
+		      "Value=1 is not converted to \"1\"");
+
+	len = u8_to_dec(text, sizeof(text), 11);
+	zassert_equal(len, 2, "Length of 11 is not 2");
+	zassert_equal(strcmp(text, "11"), 0,
+		      "Value=10 is not converted to \"11\"");
+
+	len = u8_to_dec(text, sizeof(text), 100);
+	zassert_equal(len, 3, "Length of 100 is not 3");
+	zassert_equal(strcmp(text, "100"), 0,
+		      "Value=100 is not converted to \"100\"");
+
+	len = u8_to_dec(text, sizeof(text), 101);
+	zassert_equal(len, 3, "Length of 101 is not 3");
+	zassert_equal(strcmp(text, "101"), 0,
+		      "Value=101 is not converted to \"101\"");
+
+	len = u8_to_dec(text, sizeof(text), 255);
+	zassert_equal(len, 3, "Length of 255 is not 3");
+	zassert_equal(strcmp(text, "255"), 0,
+		      "Value=255 is not converted to \"255\"");
+
+	memset(text, 0, sizeof(text));
+	len = u8_to_dec(text, 2, 123);
+	zassert_equal(len, 2,
+		      "Length of converted value using 2 byte buffer isn't 2");
+	zassert_equal(
+		strcmp(text, "12"), 0,
+		"Value=123 is not converted to \"12\" using 2-byte buffer");
+
+	memset(text, 0, sizeof(text));
+	len = u8_to_dec(text, 1, 123);
+	zassert_equal(len, 1,
+		      "Length of converted value using 1 byte buffer isn't 1");
+	zassert_equal(
+		strcmp(text, "1"), 0,
+		"Value=123 is not converted to \"1\" using 1-byte buffer");
+
+	memset(text, 0, sizeof(text));
+	len = u8_to_dec(text, 0, 123);
+	zassert_equal(len, 0,
+		      "Length of converted value using 0 byte buffer isn't 0");
+}
+
+void test_main(void)
+{
+	ztest_test_suite(test_lib_sys_util_tests,
+		ztest_unit_test(test_u8_to_dec)
+	);
+
+	ztest_run_test_suite(test_lib_sys_util_tests);
+}

tests/lib/sys/util/testcase.yaml

@@ -0,0 +1,3 @@
+tests:
+  libraries.sys.util.dec:
+    tags: lib_sys_util_tests