opal/util/string_copy: add "safe" string copy function

Do essentially the same thing as strncpy(3), but a) ensure to always
terminate the destination buffer with a \0, and b) do not \0-pad to
the right.

Signed-off-by: Jeff Squyres <jsquyres@cisco.com>

opal/util/Makefile.am

@@ -71,6 +71,7 @@ headers = \
         show_help_lex.h \
         stacktrace.h \
         strncpy.h \
+        string_copy.h \
         sys_limits.h \
         timings.h \
         uri.h \
@@ -110,6 +111,7 @@ libopalutil_la_SOURCES = \
         show_help_lex.l \
         stacktrace.c \
         strncpy.c \
+        string_copy.c \
         sys_limits.c \
         uri.c \
         info_subscriber.c \

opal/util/string_copy.c

@@ -0,0 +1,28 @@
+/*
+ * Copyright (c) 2018 Cisco Systems, Inc.  All rights reserved.
+ * $COPYRIGHT$
+ *
+ * Additional copyrights may follow
+ *
+ * $HEADER$
+ */
+
+#include "opal_config.h"
+
+#include "opal/util/string_copy.h"
+
+
+void opal_string_copy(char *dest, const char *src, size_t len)
+{
+    size_t i;
+    char *new_dest = dest;
+
+    for (i = 0; i < len; ++i, ++src, ++new_dest) {
+        *new_dest = *src;
+        if ('\0' == *src) {
+            return;
+        }
+    }
+
+    dest[i - 1] = '\0';
+}

opal/util/string_copy.h

@@ -0,0 +1,62 @@
+/*
+ * Copyright (c) 2004-2005 The Trustees of Indiana University and Indiana
+ *                         University Research and Technology
+ *                         Corporation.  All rights reserved.
+ * Copyright (c) 2004-2006 The University of Tennessee and The University
+ *                         of Tennessee Research Foundation.  All rights
+ *                         reserved.
+ * Copyright (c) 2004-2005 High Performance Computing Center Stuttgart,
+ *                         University of Stuttgart.  All rights reserved.
+ * Copyright (c) 2004-2005 The Regents of the University of California.
+ *                         All rights reserved.
+ * $COPYRIGHT$
+ *
+ * Additional copyrights may follow
+ *
+ * $HEADER$
+ */
+
+#ifndef OPAL_STRING_COPY_H
+#define OPAL_STRING_COPY_H
+
+#include "opal_config.h"
+#ifdef HAVE_SYS_TYPES_H
+#include <sys/types.h>
+#endif
+
+BEGIN_C_DECLS
+
+/**
+ * Do a "safe" string copy (i.e., guarantee to \0-terminate the
+ * destination string).
+ *
+ * @param dest Destination string buffer.
+ * @param src Source string buffer.
+ * @param len Length of the destination string buffer.
+ *
+ * This function is similar to, but different than, strcpy() and
+ * strncpy().
+ *
+ * It is invalid to pass NULL for either dest or src.
+ *
+ * There is no return value.
+ *
+ * This function will essentially do the same thing as strncpy(),
+ * except that a) it will guarantee to to terminate the destination
+ * string with a \0, and b) it will not \0-pad to the right.
+ * Specifically:
+ *
+ * - If the length of the source string is less than (len), the entire
+ *   source string will be copied to the destination, including the
+ *   \0.
+ * - If the length of the source string is greater than (len), then
+ *   (len-1) characters of the source string will be copied to the
+ *   destination, and dest[len-1] will be set to '\0'.
+ */
+OPAL_DECLSPEC void opal_string_copy(char *dest, const char *src,
+                                    size_t len)
+    __opal_attribute_nonnull__(1) __opal_attribute_nonnull__(2);
+
+END_C_DECLS
+
+#endif /* OPAL_STRING_COPY_H */