func_math: Add DIGIT_SUM function.

Add a function (DIGIT_SUM) which returns the digit sum of a number.

Resolves: #1499

UserNote: The DIGIT_SUM function can be used to return the digit sum of
a number.

diff --git a/funcs/func_math.c b/funcs/func_math.c
index 5c6886613023abb3a2e4992de3de1a9e220ee1cf..9f0ceaa398da15dc81b1a983221b7e4f4319254f 100644 (file)
--- a/funcs/func_math.c
+++ b/funcs/func_math.c
@@ -177,6 +177,28 @@
                        </example>
                </description>
        </function>
+       <function name="DIGIT_SUM" language="en_US">
+               <since>
+                       <version>23.1.0</version>
+                       <version>22.7.0</version>
+                       <version>20.17.0</version>
+               </since>
+               <synopsis>
+                       Returns the sum of all the digits in a number.
+               </synopsis>
+               <syntax>
+                       <parameter name="num" />
+               </syntax>
+               <description>
+                       <para>Returns the numeric sum of all the individual digits in a number, summed up.</para>
+                       <para>This can be useful for computing checksums based on the number,
+                       where errors are typically digits being off by one.</para>
+                       <example title="Get the sum of digits in 859">
+                       same => n,Set(digitsum=${DIGIT_SUM(859)}) ; assigns digitsum=22
+                       same => n,Set(checksum=$[${digitsum} % 10]) ; assigns checksum=2
+                       </example>
+               </description>
+       </function>
  ***/
 
 enum TypeOfFunctions {
@@ -634,6 +656,27 @@ static int acf_abs_exec(struct ast_channel *chan, const char *cmd,
        return 0;
 }
 
+static int acf_digit_sum_exec(struct ast_channel *chan, const char *cmd,
+                        char *parse, char *buffer, size_t buflen)
+{
+       int sum = 0;
+
+       if (ast_strlen_zero(parse)) {
+               ast_log(LOG_WARNING, "Missing argument for number\n");
+               return -1;
+       }
+
+       for (; *parse; parse++) {
+               if (*parse < '0' || *parse > '9') {
+                       continue;
+               }
+               sum += (*parse - '0');
+       }
+
+       snprintf(buffer, buflen, "%d", sum);
+       return 0;
+}
+
 static struct ast_custom_function math_function = {
        .name = "MATH",
        .read = math
@@ -667,6 +710,11 @@ static struct ast_custom_function acf_abs = {
        .read_max = 12,
 };
 
+static struct ast_custom_function acf_digit_sum = {
+       .name = "DIGIT_SUM",
+       .read = acf_digit_sum_exec,
+};
+
 #ifdef TEST_FRAMEWORK
 AST_TEST_DEFINE(test_MATH_function)
 {
@@ -728,6 +776,7 @@ static int unload_module(void)
        res |= ast_custom_function_unregister(&acf_min);
        res |= ast_custom_function_unregister(&acf_max);
        res |= ast_custom_function_unregister(&acf_abs);
+       res |= ast_custom_function_unregister(&acf_digit_sum);
        AST_TEST_UNREGISTER(test_MATH_function);
 
        return res;
@@ -743,6 +792,7 @@ static int load_module(void)
        res |= ast_custom_function_register(&acf_min);
        res |= ast_custom_function_register(&acf_max);
        res |= ast_custom_function_register(&acf_abs);
+       res |= ast_custom_function_register(&acf_digit_sum);
        AST_TEST_REGISTER(test_MATH_function);
 
        return res;