Added epicsStrnDup() and dbmfStrndup() routines

The JSON parser passes string arguments with a length
instead or nil-terminating them. These routines make it
simple to copy such strings into either permanent or
temporary storage.

src/libCom/dbmf/dbmf.c

@@ -158,10 +158,18 @@ void* dbmfMalloc(size_t size)
 
 char * dbmfStrdup(const char *str)
 {
-	size_t len = strlen(str);
-	char *buf = dbmfMalloc(len + 1);
-	strcpy(buf, str);
-	return buf;
+    size_t len = strlen(str);
+    char *buf = dbmfMalloc(len + 1);    /* FIXME Can return NULL */
+
+    return strcpy(buf, str);
+}
+
+char * dbmfStrndup(const char *str, size_t len)
+{
+    char *buf = dbmfMalloc(len + 1);    /* FIXME Can return NULL */
+
+    buf[len] = '\0';
+    return strncpy(buf, str, len);
 }
 
 void dbmfFree(void* mem)

src/libCom/dbmf/dbmf.h

@@ -26,6 +26,7 @@ extern "C" {
 epicsShareFunc int dbmfInit(size_t size, int chunkItems);
 epicsShareFunc void * dbmfMalloc(size_t bytes);
 epicsShareFunc char * dbmfStrdup(const char *str);
+epicsShareFunc char * dbmfStrndup(const char *str, size_t len);
 epicsShareFunc char * dbmfStrcat3(const char *lhs, const char *mid,
     const char *rhs);
 epicsShareFunc void dbmfFree(void *bytes);

src/libCom/misc/epicsString.c

@@ -223,6 +223,15 @@ int epicsStrnCaseCmp(const char *s1, const char *s2, size_t len)
     return 0;
 }
 
+char * epicsStrnDup(const char *s, size_t len)
+{
+    char *buf = mallocMustSucceed(len + 1, "epicsStrnDup");
+
+    strncpy(buf, s, len);
+    buf[len] = '\0';
+    return buf;
+}
+
 char * epicsStrDup(const char *s)
 {
     return strcpy(mallocMustSucceed(strlen(s)+1, "epicsStrDup"), s);

src/libCom/misc/epicsString.h

@@ -32,6 +32,7 @@ epicsShareFunc size_t epicsStrnEscapedFromRawSize(const char *buf, size_t len);
 epicsShareFunc int epicsStrCaseCmp(const char *s1, const char *s2);
 epicsShareFunc int epicsStrnCaseCmp(const char *s1, const char *s2, size_t len);
 epicsShareFunc char * epicsStrDup(const char *s);
+epicsShareFunc char * epicsStrnDup(const char *s, size_t len);
 epicsShareFunc int epicsStrPrintEscaped(FILE *fp, const char *s, size_t n);
 #define epicsStrSnPrintEscaped epicsStrnEscapedFromRaw
 epicsShareFunc int epicsStrGlobMatch(const char *str, const char *pattern);