diff --git a/src/str.c b/src/str.c
new file mode 100644
index 0000000..323da24
--- /dev/null
+++ b/src/str.c
@@ -0,0 +1,37 @@
+
+#include "str.h"
+
+int string_cmp(char *s1,char *s2, int maxlength) {
+  int i=0;
+  while(*s1 && *s2 && (maxlength==0 || i<maxlength)) { if (*s1!=*s2) return 0; s1++; s2++; i++;}
+  if ((maxlength==0 || i<maxlength) && (*s1 || *s2)) return 0; // only partial match  
+  return 1;
+}
+
+void string_copy(char *dst,char *src, int length) {
+  int i=0;
+  while(*src && (length==0 || i<length)) { *dst=*src; dst++; src++; i++;}
+  *dst=0;
+}
+/*
+  Concat two null-terminated strings dst=dst+src
+*/
+void string_concat(char *dst,char *src) {
+  while (*dst) dst++;
+  while (*src) { *dst=*src; dst++; src++; }
+  *dst=0;
+}
+
+/*
+ Add predix to destiantion sting dst=src+dst
+*/
+void string_rconcat(char *dst,char *prefix) {
+  char *p,*q;
+  int i,pn=string_length(dst),qn=string_length(prefix);
+  for(i=0;i<qn;i++) { dst[i+qn]=dst[i]; dst[i]=prefix[i]; } 
+}
+
+int string_length(char *s) {
+  char *start=s; while (*s) s++;
+  return (int)(s-start); 
+}