add epicsStrnLen()

Base currently requires only POSIX 2001 while
strnlen() is part of POSIX 2008.

src/libCom/misc/epicsString.c

@@ -239,6 +239,18 @@ int epicsStrPrintEscaped(FILE *fp, const char *s, size_t len)
    return nout;
 }
 
+/* Until Base requires POSIX 2008 we must provide our own implementation */
+size_t epicsStrnLen(const char *s, size_t maxlen)
+{
+    size_t i;
+
+    for (i=0; i<maxlen; i++) {
+        if(s[i]=='\0')
+            return i;
+    }
+    return i;
+}
+
 int epicsStrGlobMatch(const char *str, const char *pattern)
 {
     const char *cp = NULL, *mp = NULL;

src/libCom/misc/epicsString.h

@@ -33,6 +33,7 @@ epicsShareFunc int epicsStrnCaseCmp(const char *s1, const char *s2, size_t len);
 epicsShareFunc char * epicsStrDup(const char *s);
 epicsShareFunc int epicsStrPrintEscaped(FILE *fp, const char *s, size_t n);
 #define epicsStrSnPrintEscaped epicsStrnEscapedFromRaw
+epicsShareFunc size_t epicsStrnLen(const char *s, size_t maxlen);
 epicsShareFunc int epicsStrGlobMatch(const char *str, const char *pattern);
 epicsShareFunc char * epicsStrtok_r(char *s, const char *delim, char **lasts);
 epicsShareFunc unsigned int epicsStrHash(const char *str, unsigned int seed);

src/libCom/test/epicsStringTest.c

@@ -51,7 +51,7 @@ MAIN(epicsStringTest)
     char *s;
     int status;
 
-    testPlan(299);
+    testPlan(303);
 
     testChars();
 
@@ -86,6 +86,11 @@ MAIN(epicsStringTest)
     testOk1(epicsStrHash(abcd, 0) == epicsMemHash(abcde, 4, 0));
     testOk1(epicsStrHash(abcd, 0) != epicsMemHash("abcd\0", 5, 0));
 
+    testOk1(epicsStrnLen("abcd", 5)==4);
+    testOk1(epicsStrnLen("abcd", 4)==4);
+    testOk1(epicsStrnLen("abcd", 3)==3);
+    testOk1(epicsStrnLen("abcd", 0)==0);
+
     memset(result, 'x', sizeof(result));
     status = epicsStrnEscapedFromRaw(result, 4, ABCD, 3);
     testOk(status == 3, "epicsStrnEscapedFromRaw returned %d (exp. 3)", status);