strndump function implementation

AUTHORS

@@ -22,3 +22,4 @@ under the licensing terms detailed in LICENSE.
 * Brian Anderson <[email protected]>
 * Jon Bardin <[email protected]>
 * Jukka Jyl�nki <[email protected]>
+* Aleksander Guryanov <[email protected]>

src/library.js

@@ -4199,6 +4199,24 @@ LibraryManager.library = {
     return newStr;
   },
 
+  strndup__deps: ['strdup'],
+  strndup: function(ptr, size) {
+    var len = String_len(ptr);
+
+    if (size >= len) {
+      return _strdup(ptr);
+    }
+
+    if (size < 0) {
+      size = 0;
+    }
+
+    var newStr = _malloc(size + 1);
+    {{{ makeCopyValues('newStr', 'ptr', 'size', 'null', null, 1) }}};
+    {{{ makeSetValue('newStr', 'size', '0', 'i8') }}};
+    return newStr;
+  },
+
   strpbrk: function(ptr1, ptr2) {
     var searchSet = Runtime.set.apply(null, String_copy(ptr2));
     while ({{{ makeGetValue('ptr1', 0, 'i8') }}}) {

tests/runner.py

@@ -1393,6 +1393,48 @@ def test_strings(self):
         '''
         self.do_run(src, '4:10,177,543,def\n4\nwowie\ntoo\n76\n5\n(null)\n/* a comment */\n// another\ntest\n', ['wowie', 'too', '74'])
 
+    def test_strndup(self):
+        src = '''
+          //---------------
+          //- http://pubs.opengroup.org/onlinepubs/9699919799/functions/strndup.html
+          //---------------
+
+          #include <stdio.h>
+          #include <stdlib.h>
+          #include <string.h>
+
+          int main(int argc, char **argv) {
+            const char* source = "strndup - duplicate a specific number of bytes from a string";
+
+            char* strdup_val = strndup(source, 0);
+            printf("1:%s\\n", strdup_val);
+            free(strdup_val);
+
+            strdup_val = strndup(source, 7);
+            printf("2:%s\\n", strdup_val);
+            free(strdup_val);
+
+            strdup_val = strndup(source, 1000);
+            printf("3:%s\\n", strdup_val);
+            free(strdup_val);
+
+            strdup_val = strndup(source, 60);
+            printf("4:%s\\n", strdup_val);
+            free(strdup_val);
+
+            strdup_val = strndup(source, 19);
+            printf("5:%s\\n", strdup_val);
+            free(strdup_val);
+
+            strdup_val = strndup(source, -1);
+            printf("6:%s\\n", strdup_val);
+            free(strdup_val);
+
+            return 0;
+          }
+        '''
+        self.do_run(src, '1:\n2:strndup\n3:strndup - duplicate a specific number of bytes from a string\n4:strndup - duplicate a specific number of bytes from a string\n5:strndup - duplicate\n6:\n')
+
     def test_errar(self):
         src = r'''
           #include <stdio.h>