[cli] allow to define ping interval in milliseconds (#3607)

src/cli/README.md

@@ -1399,6 +1399,10 @@ Done
 
 Send an ICMPv6 Echo Request.
 
+* size: The number of data bytes to be sent.
+* count: The number of ICMPv6 Echo Requests to be sent.
+* interval: The interval between two consecutive ICMPv6 Echo Requests in seconds. The value may have fractional form, for example `0.5`.
+
 ```bash
 > ping fdde:ad00:beef:0:558:f56b:d688:799
 16 bytes from fdde:ad00:beef:0:558:f56b:d688:799: icmp_seq=1 hlim=64 time=28ms

src/cli/cli.cpp

@@ -418,6 +418,52 @@ otError Interpreter::ParseUnsignedLong(char *argv, unsigned long &value)
     return (*endptr == '\0') ? OT_ERROR_NONE : OT_ERROR_PARSE;
 }
 
+otError Interpreter::ParsePingInterval(const char *aString, uint32_t &aInterval)
+{
+    otError        error    = OT_ERROR_NONE;
+    const uint32_t msFactor = 1000;
+    uint32_t       factor   = msFactor;
+
+    aInterval = 0;
+
+    while (*aString)
+    {
+        if ('0' <= *aString && *aString <= '9')
+        {
+            // In the case of seconds, change the base of already calculated value.
+            if (factor == msFactor)
+            {
+                aInterval *= 10;
+            }
+
+            aInterval += static_cast<uint32_t>(*aString - '0') * factor;
+
+            // In the case of milliseconds, change the multiplier factor.
+            if (factor != msFactor)
+            {
+                factor /= 10;
+            }
+        }
+        else if (*aString == '.')
+        {
+            // Accept only one dot character.
+            VerifyOrExit(factor == msFactor, error = OT_ERROR_PARSE);
+
+            // Start analyzing hundreds of milliseconds.
+            factor /= 10;
+        }
+        else
+        {
+            ExitNow(error = OT_ERROR_PARSE);
+        }
+
+        aString++;
+    }
+
+exit:
+    return error;
+}
+
 void Interpreter::ProcessHelp(int argc, char *argv[])
 {
     OT_UNUSED_VARIABLE(argc);
@@ -1926,9 +1972,10 @@ exit:
 
 void Interpreter::ProcessPing(int argc, char *argv[])
 {
-    otError error = OT_ERROR_NONE;
-    uint8_t index = 1;
-    long    value;
+    otError  error = OT_ERROR_NONE;
+    uint8_t  index = 1;
+    long     value;
+    uint32_t interval;
 
     VerifyOrExit(argc > 0, error = OT_ERROR_INVALID_ARGS);
 
@@ -1957,21 +2004,22 @@ void Interpreter::ProcessPing(int argc, char *argv[])
 
     while (index < argc)
     {
-        SuccessOrExit(error = ParseLong(argv[index], value));
-
         switch (index)
         {
         case 1:
+            SuccessOrExit(error = ParseLong(argv[index], value));
             mLength = static_cast<uint16_t>(value);
             break;
 
         case 2:
+            SuccessOrExit(error = ParseLong(argv[index], value));
             mCount = static_cast<uint16_t>(value);
             break;
 
         case 3:
-            VerifyOrExit(0 < value && value <= Timer::kMaxDt / 1000, error = OT_ERROR_INVALID_ARGS);
-            mInterval = static_cast<uint32_t>(value) * 1000;
+            SuccessOrExit(error = ParsePingInterval(argv[index], interval));
+            VerifyOrExit(0 < interval && interval <= Timer::kMaxDt, error = OT_ERROR_INVALID_ARGS);
+            mInterval = interval;
             break;
 
         default:

src/cli/cli.hpp

@@ -188,10 +188,11 @@ private:
         kDefaultJoinerTimeout = 120, ///< Default timeout for Joiners, in seconds.
     };
 
-    void ProcessHelp(int argc, char *argv[]);
-    void ProcessAutoStart(int argc, char *argv[]);
-    void ProcessBufferInfo(int argc, char *argv[]);
-    void ProcessChannel(int argc, char *argv[]);
+    otError ParsePingInterval(const char *aString, uint32_t &aInterval);
+    void    ProcessHelp(int argc, char *argv[]);
+    void    ProcessAutoStart(int argc, char *argv[]);
+    void    ProcessBufferInfo(int argc, char *argv[]);
+    void    ProcessChannel(int argc, char *argv[]);
 #if OPENTHREAD_FTD
     void ProcessChild(int argc, char *argv[]);
     void ProcessChildMax(int argc, char *argv[]);