util/StringCompare: add StringIsEmpty()

src/db/update/Archive.cxx

@@ -31,6 +31,7 @@
 #include "archive/ArchiveFile.hxx"
 #include "archive/ArchiveVisitor.hxx"
 #include "util/Error.hxx"
+#include "util/StringCompare.hxx"
 #include "Log.hxx"
 
 #include <string>
@@ -54,7 +55,7 @@ UpdateWalk::UpdateArchiveTree(Directory &directory, const char *name)
 		//create directories first
 		UpdateArchiveTree(*subdir, tmp + 1);
 	} else {
-		if (strlen(name) == 0) {
+		if (StringIsEmpty(name)) {
 			LogWarning(update_domain,
 				   "archive returned directory only");
 			return;

src/db/update/InotifyQueue.cxx

@@ -22,6 +22,7 @@
 #include "InotifyDomain.hxx"
 #include "Service.hxx"
 #include "Log.hxx"
+#include "util/StringCompare.hxx"
 
 #include <string.h>
 
@@ -59,7 +60,7 @@ path_in(const char *path, const char *possible_parent)
 {
 	size_t length = strlen(possible_parent);
 
-	return path[0] == 0 ||
+	return StringIsEmpty(path) ||
 		(memcmp(possible_parent, path, length) == 0 &&
 		 (path[length] == 0 || path[length] == '/'));
 }

src/db/update/Walk.cxx

@@ -38,6 +38,7 @@
 #include "fs/Charset.hxx"
 #include "storage/FileInfo.hxx"
 #include "util/Alloc.hxx"
+#include "util/StringCompare.hxx"
 #include "util/UriUtil.hxx"
 #include "util/Error.hxx"
 #include "Log.hxx"
@@ -435,7 +436,7 @@ UpdateWalk::DirectoryMakeUriParentChecked(Directory &root, const char *uri)
 	while ((slash = strchr(name_utf8, '/')) != nullptr) {
 		*slash = 0;
 
-		if (*name_utf8 == 0)
+		if (StringIsEmpty(name_utf8))
 			continue;
 
 		directory = DirectoryMakeChildChecked(*directory,