[code-utils] adding helper macro OT_ARRAY_LENGTH() (#2743)

This commit adds helper macro `OT_ARRAY_LENGTH()` to get the number
of elements in an array.

tests/unit/test_child.cpp

@@ -32,6 +32,7 @@
 #include <openthread/openthread.h>
 
 #include "test_util.h"
+#include "common/code_utils.hpp"
 #include "common/instance.hpp"
 #include "thread/topology.hpp"
 
@@ -132,7 +133,7 @@ void TestChildIp6Address(void)
 
     numAddresses++;
 
-    for (uint8_t index = 0; index < static_cast<uint8_t>(sizeof(ip6Addresses) / sizeof(ip6Addresses[0])); index++)
+    for (uint8_t index = 0; index < static_cast<uint8_t>(OT_ARRAY_LENGTH(ip6Addresses)); index++)
     {
         VerifyOrQuit(numAddresses < kMaxChildIp6Addresses, "Too many IPv6 addresses in the unit test");
         SuccessOrQuit(addresses[numAddresses++].FromString(ip6Addresses[index]),

tests/unit/test_child_table.cpp

@@ -32,6 +32,7 @@
 #include <openthread/openthread.h>
 
 #include "test_util.h"
+#include "common/code_utils.hpp"
 #include "common/instance.hpp"
 #include "thread/child_table.hpp"
 
@@ -109,7 +110,7 @@ void VerifyChildTableContent(ChildTable &aTable, uint8_t aChildListLength, const
 {
     printf("Test ChildTable with %d entries", aChildListLength);
 
-    for (uint8_t k = 0; k < sizeof(kAllFilters) / sizeof(kAllFilters[0]); k++)
+    for (uint8_t k = 0; k < OT_ARRAY_LENGTH(kAllFilters); k++)
     {
         ChildTable::StateFilter filter = kAllFilters[k];
 
@@ -296,7 +297,7 @@ void TestChildTable(void)
         },
     };
 
-    const uint8_t testListLength = sizeof(testChildList) / sizeof(testChildList[0]);
+    const uint8_t testListLength = OT_ARRAY_LENGTH(testChildList);
 
     uint8_t testNumAllowedChildren = 2;
 
@@ -314,7 +315,7 @@ void TestChildTable(void)
     VerifyOrQuit(table->GetMaxChildrenAllowed() == table->GetMaxChildren(),
                  "GetMaxChildrenAllowed() initial value is incorrect ");
 
-    for (uint8_t i = 0; i < sizeof(kAllFilters) / sizeof(kAllFilters[0]); i++)
+    for (uint8_t i = 0; i < OT_ARRAY_LENGTH(kAllFilters); i++)
     {
         ChildTable::StateFilter filter = kAllFilters[i];
 

tests/unit/test_link_quality.cpp

@@ -28,6 +28,7 @@
 
 #include <openthread/openthread.h>
 
+#include "common/code_utils.hpp"
 #include "thread/link_quality.hpp"
 #include "utils/wrap_string.h"
 
@@ -427,7 +428,7 @@ void TestSuccessRateTracker(void)
 
     // Adding success/failure at different rates and checking the RateTracker rate for every sample
 
-    for (uint16_t testRound = 0; testRound < sizeof(kWeightLimit) / sizeof(kWeightLimit[0]) * 2; testRound++)
+    for (uint16_t testRound = 0; testRound < OT_ARRAY_LENGTH(kWeightLimit) * 2; testRound++)
     {
         uint16_t weightLimit;
         bool     reverseLogic;

tests/unit/test_mac_frame.cpp

@@ -28,6 +28,7 @@
 
 #include <openthread/openthread.h>
 
+#include "common/code_utils.hpp"
 #include "common/debug.hpp"
 #include "mac/mac.hpp"
 #include "mac/mac_frame.hpp"
@@ -68,7 +69,7 @@ void TestMacHeader(void)
          Mac::Frame::kSecMic32 | Mac::Frame::kKeyIdMode2, 19},
     };
 
-    for (unsigned i = 0; i < sizeof(tests) / sizeof(tests[0]); i++)
+    for (unsigned i = 0; i < OT_ARRAY_LENGTH(tests); i++)
     {
         uint8_t    psdu[Mac::Frame::kMTU];
         Mac::Frame frame;

tests/unit/test_network_data.cpp

@@ -28,6 +28,7 @@
 
 #include <openthread/config.h>
 
+#include "common/code_utils.hpp"
 #include "common/instance.hpp"
 #include "thread/network_data_local.hpp"
 
@@ -108,7 +109,7 @@ void TestNetworkDataIterator(void)
         printf("\nTest #1: Network data 1");
         printf("\n-------------------------------------------------");
 
-        for (uint8_t i = 0; i < sizeof(routes) / sizeof(routes[0]); i++)
+        for (uint8_t i = 0; i < OT_ARRAY_LENGTH(routes); i++)
         {
             SuccessOrQuit(netData.GetNextExternalRoute(&iter, &config), "GetNextExternalRoute() failed\n");
             PrintExternalRouteConfig(config);
@@ -158,7 +159,7 @@ void TestNetworkDataIterator(void)
         printf("\nTest #2: Network data 2");
         printf("\n-------------------------------------------------");
 
-        for (uint8_t i = 0; i < sizeof(routes) / sizeof(routes[0]); i++)
+        for (uint8_t i = 0; i < OT_ARRAY_LENGTH(routes); i++)
         {
             SuccessOrQuit(netData.GetNextExternalRoute(&iter, &config), "GetNextExternalRoute() failed\n");
             PrintExternalRouteConfig(config);

tests/unit/test_timer.cpp

@@ -28,6 +28,7 @@
 
 #include "test_platform.h"
 
+#include "common/code_utils.hpp"
 #include "common/debug.hpp"
 #include "common/instance.hpp"
 #include "common/timer.hpp"
@@ -550,7 +551,7 @@ int TestTenTimers(void)
 
     size_t i;
 
-    for (i = 0; i < sizeof(kTimeShift) / sizeof(kTimeShift[0]); i++)
+    for (i = 0; i < OT_ARRAY_LENGTH(kTimeShift); i++)
     {
         TenTimers(kTimeShift[i]);
     }